@ Documentation/admin-guide/kernel-parameters.txt:6541 @ Force threading of all interrupt handlers except those marked explicitly IRQF_NO_THREAD. + threadprintk [KNL] + Force threaded printing of all legacy consoles. Be + aware that with this option, the shutdown, reboot, and + panic messages may not be printed on the legacy + consoles. Also, earlycon/earlyprintk printing will be + delayed until a regular console or the kthread is + available. + + Users can view /proc/consoles to see if their console + driver is legacy or not. Non-legacy (NBCON) console + drivers are already threaded and are shown with 'N'. + topology= [S390,EARLY] Format: {off | on} Specify if the kernel should make use of the cpu @ arch/arm/Kconfig:40 @ config ARM select ARCH_SUPPORTS_ATOMIC_RMW select ARCH_SUPPORTS_HUGETLBFS if ARM_LPAE select ARCH_SUPPORTS_PER_VMA_LOCK + select ARCH_SUPPORTS_RT if HAVE_POSIX_CPU_TIMERS_TASK_WORK select ARCH_USE_BUILTIN_BSWAP select ARCH_USE_CMPXCHG_LOCKREF select ARCH_USE_MEMTEST @ arch/arm/Kconfig:80 @ config ARM select HAS_IOPORT select HAVE_ARCH_AUDITSYSCALL if AEABI && !OABI_COMPAT select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6 - select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU + select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU && !PREEMPT_RT select HAVE_ARCH_KFENCE if MMU && !XIP_KERNEL select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU select HAVE_ARCH_KASAN if MMU && !XIP_KERNEL @ arch/arm/Kconfig:103 @ config ARM select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE select HAVE_EFFICIENT_UNALIGNED_ACCESS if (CPU_V6 || CPU_V6K || CPU_V7) && MMU select HAVE_EXIT_THREAD - select HAVE_FAST_GUP if ARM_LPAE + select HAVE_FAST_GUP if ARM_LPAE && !(PREEMPT_RT && HIGHPTE) select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL select HAVE_FUNCTION_ERROR_INJECTION select HAVE_FUNCTION_GRAPH_TRACER @ arch/arm/Kconfig:126 @ config ARM select HAVE_PERF_EVENTS select HAVE_PERF_REGS select HAVE_PERF_USER_STACK_DUMP + select HAVE_POSIX_CPU_TIMERS_TASK_WORK if !KVM select MMU_GATHER_RCU_TABLE_FREE if SMP && ARM_LPAE select HAVE_REGS_AND_STACK_ACCESS_API select HAVE_RSEQ @ arch/arm/mm/fault.c:446 @ do_translation_fault(unsigned long addr, unsigned int fsr, if (addr < TASK_SIZE) return do_page_fault(addr, fsr, regs); + if (interrupts_enabled(regs)) + local_irq_enable(); + if (user_mode(regs)) goto bad_area; @ arch/arm/mm/fault.c:519 @ do_translation_fault(unsigned long addr, unsigned int fsr, static int do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs) { + if (interrupts_enabled(regs)) + local_irq_enable(); + do_bad_area(addr, fsr, regs); return 0; } @ arch/arm/vfp/vfpmodule.c:58 @ extern unsigned int VFP_arch_feroceon __alias(VFP_arch); */ union vfp_state *vfp_current_hw_state[NR_CPUS]; +/* + * Claim ownership of the VFP unit. + * + * The caller may change VFP registers until vfp_unlock() is called. + * + * local_bh_disable() is used to disable preemption and to disable VFP + * processing in softirq context. On PREEMPT_RT kernels local_bh_disable() is + * not sufficient because it only serializes soft interrupt related sections + * via a local lock, but stays preemptible. Disabling preemption is the right + * choice here as bottom half processing is always in thread context on RT + * kernels so it implicitly prevents bottom half processing as well. + */ +static void vfp_lock(void) +{ + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + local_bh_disable(); + else + preempt_disable(); +} + +static void vfp_unlock(void) +{ + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + local_bh_enable(); + else + preempt_enable(); +} + /* * Is 'thread's most up to date state stored in this CPUs hardware? * Must be called from non-preemptible context. @ arch/arm/vfp/vfpmodule.c:271 @ static void vfp_panic(char *reason, u32 inst) /* * Process bitmask of exception conditions. */ -static void vfp_raise_exceptions(u32 exceptions, u32 inst, u32 fpscr, struct pt_regs *regs) +static int vfp_raise_exceptions(u32 exceptions, u32 inst, u32 fpscr) { int si_code = 0; @ arch/arm/vfp/vfpmodule.c:279 @ static void vfp_raise_exceptions(u32 exceptions, u32 inst, u32 fpscr, struct pt_ if (exceptions == VFP_EXCEPTION_ERROR) { vfp_panic("unhandled bounce", inst); - vfp_raise_sigfpe(FPE_FLTINV, regs); - return; + return FPE_FLTINV; } /* @ arch/arm/vfp/vfpmodule.c:307 @ static void vfp_raise_exceptions(u32 exceptions, u32 inst, u32 fpscr, struct pt_ RAISE(FPSCR_OFC, FPSCR_OFE, FPE_FLTOVF); RAISE(FPSCR_IOC, FPSCR_IOE, FPE_FLTINV); - if (si_code) - vfp_raise_sigfpe(si_code, regs); + return si_code; } /* @ arch/arm/vfp/vfpmodule.c:353 @ static u32 vfp_emulate_instruction(u32 inst, u32 fpscr, struct pt_regs *regs) static void VFP_bounce(u32 trigger, u32 fpexc, struct pt_regs *regs) { u32 fpscr, orig_fpscr, fpsid, exceptions; + int si_code2 = 0; + int si_code = 0; pr_debug("VFP: bounce: trigger %08x fpexc %08x\n", trigger, fpexc); @ arch/arm/vfp/vfpmodule.c:400 @ static void VFP_bounce(u32 trigger, u32 fpexc, struct pt_regs *regs) * unallocated VFP instruction but with FPSCR.IXE set and not * on VFP subarch 1. */ - vfp_raise_exceptions(VFP_EXCEPTION_ERROR, trigger, fpscr, regs); - return; + si_code = vfp_raise_exceptions(VFP_EXCEPTION_ERROR, trigger, fpscr); + goto exit; } /* @ arch/arm/vfp/vfpmodule.c:425 @ static void VFP_bounce(u32 trigger, u32 fpexc, struct pt_regs *regs) */ exceptions = vfp_emulate_instruction(trigger, fpscr, regs); if (exceptions) - vfp_raise_exceptions(exceptions, trigger, orig_fpscr, regs); + si_code2 = vfp_raise_exceptions(exceptions, trigger, orig_fpscr); /* * If there isn't a second FP instruction, exit now. Note that * the FPEXC.FP2V bit is valid only if FPEXC.EX is 1. */ if ((fpexc & (FPEXC_EX | FPEXC_FP2V)) != (FPEXC_EX | FPEXC_FP2V)) - return; + goto exit; /* * The barrier() here prevents fpinst2 being read @ arch/arm/vfp/vfpmodule.c:444 @ static void VFP_bounce(u32 trigger, u32 fpexc, struct pt_regs *regs) emulate: exceptions = vfp_emulate_instruction(trigger, orig_fpscr, regs); if (exceptions) - vfp_raise_exceptions(exceptions, trigger, orig_fpscr, regs); + si_code = vfp_raise_exceptions(exceptions, trigger, orig_fpscr); +exit: + vfp_unlock(); + if (si_code2) + vfp_raise_sigfpe(si_code2, regs); + if (si_code) + vfp_raise_sigfpe(si_code, regs); } static void vfp_enable(void *unused) @ arch/arm/vfp/vfpmodule.c:549 @ static inline void vfp_pm_init(void) { } */ void vfp_sync_hwstate(struct thread_info *thread) { - unsigned int cpu = get_cpu(); + vfp_lock(); - local_bh_disable(); - - if (vfp_state_in_hw(cpu, thread)) { + if (vfp_state_in_hw(raw_smp_processor_id(), thread)) { u32 fpexc = fmrx(FPEXC); /* @ arch/arm/vfp/vfpmodule.c:562 @ void vfp_sync_hwstate(struct thread_info *thread) fmxr(FPEXC, fpexc); } - local_bh_enable(); - put_cpu(); + vfp_unlock(); } /* Ensure that the thread reloads the hardware VFP state on the next use. */ @ arch/arm/vfp/vfpmodule.c:717 @ static int vfp_support_entry(struct pt_regs *regs, u32 trigger) if (!user_mode(regs)) return vfp_kmode_exception(regs, trigger); - local_bh_disable(); + vfp_lock(); fpexc = fmrx(FPEXC); /* @ arch/arm/vfp/vfpmodule.c:782 @ static int vfp_support_entry(struct pt_regs *regs, u32 trigger) * replay the instruction that trapped. */ fmxr(FPEXC, fpexc); + vfp_unlock(); } else { /* Check for synchronous or asynchronous exceptions */ if (!(fpexc & (FPEXC_EX | FPEXC_DEX))) { @ arch/arm/vfp/vfpmodule.c:797 @ static int vfp_support_entry(struct pt_regs *regs, u32 trigger) if (!(fpscr & FPSCR_IXE)) { if (!(fpscr & FPSCR_LENGTH_MASK)) { pr_debug("not VFP\n"); - local_bh_enable(); + vfp_unlock(); return -ENOEXEC; } fpexc |= FPEXC_DEX; } } bounce: regs->ARM_pc += 4; + /* VFP_bounce() will invoke vfp_unlock() */ VFP_bounce(trigger, fpexc, regs); } - local_bh_enable(); return 0; } @ arch/arm/vfp/vfpmodule.c:872 @ void kernel_neon_begin(void) unsigned int cpu; u32 fpexc; - local_bh_disable(); + vfp_lock(); /* * Kernel mode NEON is only allowed outside of hardirq context with @ arch/arm/vfp/vfpmodule.c:903 @ void kernel_neon_end(void) { /* Disable the NEON/VFP unit. */ fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN); - local_bh_enable(); + vfp_unlock(); } EXPORT_SYMBOL(kernel_neon_end); @ arch/arm64/Kconfig:101 @ config ARM64 select ARCH_SUPPORTS_NUMA_BALANCING select ARCH_SUPPORTS_PAGE_TABLE_CHECK select ARCH_SUPPORTS_PER_VMA_LOCK + select ARCH_SUPPORTS_RT select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH select ARCH_WANT_COMPAT_IPC_PARSE_VERSION if COMPAT select ARCH_WANT_DEFAULT_BPF_JIT @ arch/powerpc/Kconfig:169 @ config PPC select ARCH_STACKWALK select ARCH_SUPPORTS_ATOMIC_RMW select ARCH_SUPPORTS_DEBUG_PAGEALLOC if PPC_BOOK3S || PPC_8xx || 40x + select ARCH_SUPPORTS_RT if HAVE_POSIX_CPU_TIMERS_TASK_WORK select ARCH_USE_BUILTIN_BSWAP select ARCH_USE_CMPXCHG_LOCKREF if PPC64 select ARCH_USE_MEMTEST @ arch/powerpc/Kconfig:274 @ config PPC select HAVE_PERF_USER_STACK_DUMP select HAVE_REGS_AND_STACK_ACCESS_API select HAVE_RELIABLE_STACKTRACE + select HAVE_POSIX_CPU_TIMERS_TASK_WORK if !KVM select HAVE_RSEQ select HAVE_SETUP_PER_CPU_AREA if PPC64 select HAVE_SOFTIRQ_ON_OWN_STACK @ arch/powerpc/include/asm/stackprotector.h:22 @ */ static __always_inline void boot_init_stack_canary(void) { - unsigned long canary = get_random_canary(); + unsigned long canary; +#ifndef CONFIG_PREEMPT_RT + canary = get_random_canary(); +#else + canary = ((unsigned long)&canary) & CANARY_MASK; +#endif current->stack_canary = canary; #ifdef CONFIG_PPC64 get_paca()->canary = canary; @ arch/powerpc/kernel/traps.c:264 @ static char *get_mmu_str(void) static int __die(const char *str, struct pt_regs *regs, long err) { + const char *pr = ""; + printk("Oops: %s, sig: %ld [#%d]\n", str, err, ++die_counter); + if (IS_ENABLED(CONFIG_PREEMPTION)) + pr = IS_ENABLED(CONFIG_PREEMPT_RT) ? " PREEMPT_RT" : " PREEMPT"; + printk("%s PAGE_SIZE=%luK%s%s%s%s%s%s %s\n", IS_ENABLED(CONFIG_CPU_LITTLE_ENDIAN) ? "LE" : "BE", PAGE_SIZE / 1024, get_mmu_str(), - IS_ENABLED(CONFIG_PREEMPT) ? " PREEMPT" : "", + pr, IS_ENABLED(CONFIG_SMP) ? " SMP" : "", IS_ENABLED(CONFIG_SMP) ? (" NR_CPUS=" __stringify(NR_CPUS)) : "", debug_pagealloc_enabled() ? " DEBUG_PAGEALLOC" : "", @ arch/powerpc/kvm/Kconfig:224 @ config KVM_E500MC config KVM_MPIC bool "KVM in-kernel MPIC emulation" depends on KVM && PPC_E500 + depends on !PREEMPT_RT select HAVE_KVM_IRQCHIP select HAVE_KVM_IRQ_ROUTING select HAVE_KVM_MSI @ arch/powerpc/platforms/pseries/Kconfig:5 @ config PPC_PSERIES depends on PPC64 && PPC_BOOK3S bool "IBM pSeries & new (POWER5-based) iSeries" + select GENERIC_ALLOCATOR select HAVE_PCSPKR_PLATFORM select MPIC select OF_DYNAMIC @ arch/powerpc/platforms/pseries/iommu.c:28 @ #include <linux/of_address.h> #include <linux/iommu.h> #include <linux/rculist.h> +#include <linux/local_lock.h> #include <asm/io.h> #include <asm/prom.h> #include <asm/rtas.h> @ arch/powerpc/platforms/pseries/iommu.c:210 @ static int tce_build_pSeriesLP(unsigned long liobn, long tcenum, long tceshift, return ret; } -static DEFINE_PER_CPU(__be64 *, tce_page); +struct tce_page { + __be64 * page; + local_lock_t lock; +}; +static DEFINE_PER_CPU(struct tce_page, tce_page) = { + .lock = INIT_LOCAL_LOCK(lock), +}; static int tce_buildmulti_pSeriesLP(struct iommu_table *tbl, long tcenum, long npages, unsigned long uaddr, @ arch/powerpc/platforms/pseries/iommu.c:239 @ static int tce_buildmulti_pSeriesLP(struct iommu_table *tbl, long tcenum, direction, attrs); } - local_irq_save(flags); /* to protect tcep and the page behind it */ + /* to protect tcep and the page behind it */ + local_lock_irqsave(&tce_page.lock, flags); - tcep = __this_cpu_read(tce_page); + tcep = __this_cpu_read(tce_page.page); /* This is safe to do since interrupts are off when we're called * from iommu_alloc{,_sg}() @ arch/powerpc/platforms/pseries/iommu.c:251 @ static int tce_buildmulti_pSeriesLP(struct iommu_table *tbl, long tcenum, tcep = (__be64 *)__get_free_page(GFP_ATOMIC); /* If allocation fails, fall back to the loop implementation */ if (!tcep) { - local_irq_restore(flags); + local_unlock_irqrestore(&tce_page.lock, flags); return tce_build_pSeriesLP(tbl->it_index, tcenum, tceshift, npages, uaddr, direction, attrs); } - __this_cpu_write(tce_page, tcep); + __this_cpu_write(tce_page.page, tcep); } rpn = __pa(uaddr) >> tceshift; @ arch/powerpc/platforms/pseries/iommu.c:286 @ static int tce_buildmulti_pSeriesLP(struct iommu_table *tbl, long tcenum, tcenum += limit; } while (npages > 0 && !rc); - local_irq_restore(flags); + local_unlock_irqrestore(&tce_page.lock, flags); if (unlikely(rc == H_NOT_ENOUGH_RESOURCES)) { ret = (int)rc; @ arch/powerpc/platforms/pseries/iommu.c:470 @ static int tce_setrange_multi_pSeriesLP(unsigned long start_pfn, DMA_BIDIRECTIONAL, 0); } - local_irq_disable(); /* to protect tcep and the page behind it */ - tcep = __this_cpu_read(tce_page); + /* to protect tcep and the page behind it */ + local_lock_irq(&tce_page.lock); + tcep = __this_cpu_read(tce_page.page); if (!tcep) { tcep = (__be64 *)__get_free_page(GFP_ATOMIC); if (!tcep) { - local_irq_enable(); + local_unlock_irq(&tce_page.lock); return -ENOMEM; } - __this_cpu_write(tce_page, tcep); + __this_cpu_write(tce_page.page, tcep); } proto_tce = TCE_PCI_READ | TCE_PCI_WRITE; @ arch/powerpc/platforms/pseries/iommu.c:523 @ static int tce_setrange_multi_pSeriesLP(unsigned long start_pfn, /* error cleanup: caller will clear whole range */ - local_irq_enable(); + local_unlock_irq(&tce_page.lock); return rc; } @ arch/riscv/Kconfig:59 @ config RISCV select ARCH_SUPPORTS_LTO_CLANG_THIN if LLD_VERSION >= 140000 select ARCH_SUPPORTS_PAGE_TABLE_CHECK if MMU select ARCH_SUPPORTS_PER_VMA_LOCK if MMU + select ARCH_SUPPORTS_RT select ARCH_SUPPORTS_SHADOW_CALL_STACK if HAVE_SHADOW_CALL_STACK select ARCH_USE_MEMTEST select ARCH_USE_QUEUED_RWLOCKS @ arch/riscv/Kconfig:156 @ config RISCV select HAVE_PERF_USER_STACK_DUMP select HAVE_POSIX_CPU_TIMERS_TASK_WORK select HAVE_PREEMPT_DYNAMIC_KEY if !XIP_KERNEL + select HAVE_PREEMPT_AUTO select HAVE_REGS_AND_STACK_ACCESS_API select HAVE_RETHOOK if !XIP_KERNEL select HAVE_RSEQ @ arch/riscv/include/asm/thread_info.h:97 @ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src); * - pending work-to-be-done flags are in lowest half-word * - other flags in upper half-word(s) */ +#define TIF_ARCH_RESCHED_LAZY 0 /* Lazy rescheduling */ #define TIF_NOTIFY_RESUME 1 /* callback before returning to user */ #define TIF_SIGPENDING 2 /* signal pending */ #define TIF_NEED_RESCHED 3 /* rescheduling necessary */ @ arch/riscv/include/asm/thread_info.h:108 @ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src); #define TIF_32BIT 11 /* compat-mode 32bit process */ #define TIF_RISCV_V_DEFER_RESTORE 12 /* restore Vector before returing to user */ +#define _TIF_ARCH_RESCHED_LAZY (1 << TIF_ARCH_RESCHED_LAZY) #define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME) #define _TIF_SIGPENDING (1 << TIF_SIGPENDING) #define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED) @ arch/x86/Kconfig:31 @ config X86_64 select ARCH_HAS_GIGANTIC_PAGE select ARCH_SUPPORTS_INT128 if CC_HAS_INT128 select ARCH_SUPPORTS_PER_VMA_LOCK + select ARCH_SUPPORTS_RT select HAVE_ARCH_SOFT_DIRTY select MODULES_USE_ELF_RELA select NEED_DMA_MAP_STATE @ arch/x86/Kconfig:123 @ config X86 select ARCH_USES_CFI_TRAPS if X86_64 && CFI_CLANG select ARCH_SUPPORTS_LTO_CLANG select ARCH_SUPPORTS_LTO_CLANG_THIN + select ARCH_SUPPORTS_RT select ARCH_USE_BUILTIN_BSWAP select ARCH_USE_CMPXCHG_LOCKREF if X86_CMPXCHG64 select ARCH_USE_MEMTEST @ arch/x86/Kconfig:281 @ config X86 select HAVE_STATIC_CALL select HAVE_STATIC_CALL_INLINE if HAVE_OBJTOOL select HAVE_PREEMPT_DYNAMIC_CALL + select HAVE_PREEMPT_AUTO select HAVE_RSEQ select HAVE_RUST if X86_64 select HAVE_SYSCALL_TRACEPOINTS @ arch/x86/include/asm/thread_info.h:90 @ struct thread_info { #define TIF_NOTIFY_RESUME 1 /* callback before returning to user */ #define TIF_SIGPENDING 2 /* signal pending */ #define TIF_NEED_RESCHED 3 /* rescheduling necessary */ -#define TIF_SINGLESTEP 4 /* reenable singlestep on user return*/ -#define TIF_SSBD 5 /* Speculative store bypass disable */ +#define TIF_ARCH_RESCHED_LAZY 4 /* Lazy rescheduling */ +#define TIF_SINGLESTEP 5 /* reenable singlestep on user return*/ +#define TIF_SSBD 6 /* Speculative store bypass disable */ #define TIF_SPEC_IB 9 /* Indirect branch speculation mitigation */ #define TIF_SPEC_L1D_FLUSH 10 /* Flush L1D on mm switches (processes) */ #define TIF_USER_RETURN_NOTIFY 11 /* notify kernel of userspace return */ @ arch/x86/include/asm/thread_info.h:114 @ struct thread_info { #define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME) #define _TIF_SIGPENDING (1 << TIF_SIGPENDING) #define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED) +#define _TIF_ARCH_RESCHED_LAZY (1 << TIF_ARCH_RESCHED_LAZY) #define _TIF_SINGLESTEP (1 << TIF_SINGLESTEP) #define _TIF_SSBD (1 << TIF_SSBD) #define _TIF_SPEC_IB (1 << TIF_SPEC_IB) @ drivers/acpi/processor_idle.c:111 @ static const struct dmi_system_id processor_power_dmi_table[] = { */ static void __cpuidle acpi_safe_halt(void) { - if (!tif_need_resched()) { + if (!need_resched()) { raw_safe_halt(); raw_local_irq_disable(); } @ drivers/block/zram/zram_drv.c:60 @ static void zram_free_page(struct zram *zram, size_t index); static int zram_read_page(struct zram *zram, struct page *page, u32 index, struct bio *parent); +#ifdef CONFIG_PREEMPT_RT +static void zram_meta_init_table_locks(struct zram *zram, size_t num_pages) +{ + size_t index; + + for (index = 0; index < num_pages; index++) + spin_lock_init(&zram->table[index].lock); +} + +static int zram_slot_trylock(struct zram *zram, u32 index) +{ + int ret; + + ret = spin_trylock(&zram->table[index].lock); + if (ret) + __set_bit(ZRAM_LOCK, &zram->table[index].flags); + return ret; +} + +static void zram_slot_lock(struct zram *zram, u32 index) +{ + spin_lock(&zram->table[index].lock); + __set_bit(ZRAM_LOCK, &zram->table[index].flags); +} + +static void zram_slot_unlock(struct zram *zram, u32 index) +{ + __clear_bit(ZRAM_LOCK, &zram->table[index].flags); + spin_unlock(&zram->table[index].lock); +} + +#else + +static void zram_meta_init_table_locks(struct zram *zram, size_t num_pages) { } + static int zram_slot_trylock(struct zram *zram, u32 index) { return bit_spin_trylock(ZRAM_LOCK, &zram->table[index].flags); @ drivers/block/zram/zram_drv.c:109 @ static void zram_slot_unlock(struct zram *zram, u32 index) { bit_spin_unlock(ZRAM_LOCK, &zram->table[index].flags); } +#endif static inline bool init_done(struct zram *zram) { @ drivers/block/zram/zram_drv.c:1280 @ static bool zram_meta_alloc(struct zram *zram, u64 disksize) if (!huge_class_size) huge_class_size = zs_huge_class_size(zram->mem_pool); + zram_meta_init_table_locks(zram, num_pages); return true; } @ drivers/block/zram/zram_drv.h:72 @ struct zram_table_entry { unsigned long element; }; unsigned long flags; +#ifdef CONFIG_PREEMPT_RT + spinlock_t lock; +#endif #ifdef CONFIG_ZRAM_TRACK_ENTRY_ACTIME ktime_t ac_time; #endif @ drivers/gpu/drm/i915/Kconfig:6 @ config DRM_I915 tristate "Intel 8xx/9xx/G3x/G4x/HD Graphics" depends on DRM depends on X86 && PCI - depends on !PREEMPT_RT select INTEL_GTT if X86 select INTERVAL_TREE # we need shmfs for the swappable backing store, and in particular @ drivers/gpu/drm/i915/display/intel_crtc.c:515 @ void intel_pipe_update_start(struct intel_atomic_state *state, */ intel_psr_wait_for_idle_locked(new_crtc_state); - local_irq_disable(); + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + local_irq_disable(); crtc->debug.min_vbl = evade.min; crtc->debug.max_vbl = evade.max; @ drivers/gpu/drm/i915/display/intel_crtc.c:534 @ void intel_pipe_update_start(struct intel_atomic_state *state, return; irq_disable: - local_irq_disable(); + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + local_irq_disable(); } #if IS_ENABLED(CONFIG_DRM_I915_DEBUG_VBLANK_EVADE) @ drivers/gpu/drm/i915/display/intel_crtc.c:637 @ void intel_pipe_update_end(struct intel_atomic_state *state, */ intel_vrr_send_push(new_crtc_state); - local_irq_enable(); + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + local_irq_enable(); if (intel_vgpu_active(dev_priv)) goto out; @ drivers/gpu/drm/i915/display/intel_vblank.c:279 @ int intel_crtc_scanline_to_hw(struct intel_crtc *crtc, int scanline) * all register accesses to the same cacheline to be serialized, * otherwise they may hang. */ +static void intel_vblank_section_enter_irqsave(struct drm_i915_private *i915, unsigned long *flags) + __acquires(i915->uncore.lock) +{ +#ifdef I915 + spin_lock_irqsave(&i915->uncore.lock, *flags); +#else + *flags = 0; +#endif +} + +static void intel_vblank_section_exit_irqrestore(struct drm_i915_private *i915, unsigned long flags) + __releases(i915->uncore.lock) +{ +#ifdef I915 + spin_unlock_irqrestore(&i915->uncore.lock, flags); +#else + if (flags) + return; +#endif +} static void intel_vblank_section_enter(struct drm_i915_private *i915) __acquires(i915->uncore.lock) { @ drivers/gpu/drm/i915/display/intel_vblank.c:356 @ static bool i915_get_crtc_scanoutpos(struct drm_crtc *_crtc, * timing critical raw register reads, potentially with * preemption disabled, so the following code must not block. */ - local_irq_save(irqflags); - intel_vblank_section_enter(dev_priv); + intel_vblank_section_enter_irqsave(dev_priv, &irqflags); - /* preempt_disable_rt() should go right here in PREEMPT_RT patchset. */ + if (IS_ENABLED(CONFIG_PREEMPT_RT)) + preempt_disable(); /* Get optional system timestamp before query. */ if (stime) @ drivers/gpu/drm/i915/display/intel_vblank.c:423 @ static bool i915_get_crtc_scanoutpos(struct drm_crtc *_crtc, if (etime) *etime = ktime_get(); - /* preempt_enable_rt() should go right here in PREEMPT_RT patchset. */ + if (IS_ENABLED(CONFIG_PREEMPT_RT)) + preempt_enable(); - intel_vblank_section_exit(dev_priv); - local_irq_restore(irqflags); + intel_vblank_section_exit_irqrestore(dev_priv, irqflags); /* * While in vblank, position will be negative @ drivers/gpu/drm/i915/display/intel_vblank.c:464 @ int intel_get_crtc_scanline(struct intel_crtc *crtc) unsigned long irqflags; int position; - local_irq_save(irqflags); - intel_vblank_section_enter(dev_priv); + intel_vblank_section_enter_irqsave(dev_priv, &irqflags); position = __intel_get_crtc_scanline(crtc); - intel_vblank_section_exit(dev_priv); - local_irq_restore(irqflags); + intel_vblank_section_exit_irqrestore(dev_priv, irqflags); return position; } @ drivers/gpu/drm/i915/display/intel_vblank.c:703 @ int intel_vblank_evade(struct intel_vblank_evade_ctx *evade) break; } - local_irq_enable(); + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + local_irq_enable(); timeout = schedule_timeout(timeout); - local_irq_disable(); + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + local_irq_disable(); } finish_wait(wq, &wait); @ drivers/gpu/drm/i915/gt/intel_breadcrumbs.c:320 @ void __intel_breadcrumbs_park(struct intel_breadcrumbs *b) /* Kick the work once more to drain the signalers, and disarm the irq */ irq_work_sync(&b->irq_work); while (READ_ONCE(b->irq_armed) && !atomic_read(&b->active)) { - local_irq_disable(); - signal_irq_work(&b->irq_work); - local_irq_enable(); + irq_work_queue(&b->irq_work); cond_resched(); + irq_work_sync(&b->irq_work); } } @ drivers/gpu/drm/i915/gt/intel_execlists_submission.c:1306 @ static void execlists_dequeue(struct intel_engine_cs *engine) * and context switches) submission. */ - spin_lock(&sched_engine->lock); + spin_lock_irq(&sched_engine->lock); /* * If the queue is higher priority than the last @ drivers/gpu/drm/i915/gt/intel_execlists_submission.c:1406 @ static void execlists_dequeue(struct intel_engine_cs *engine) * Even if ELSP[1] is occupied and not worthy * of timeslices, our queue might be. */ - spin_unlock(&sched_engine->lock); + spin_unlock_irq(&sched_engine->lock); return; } } @ drivers/gpu/drm/i915/gt/intel_execlists_submission.c:1432 @ static void execlists_dequeue(struct intel_engine_cs *engine) if (last && !can_merge_rq(last, rq)) { spin_unlock(&ve->base.sched_engine->lock); - spin_unlock(&engine->sched_engine->lock); + spin_unlock_irq(&engine->sched_engine->lock); return; /* leave this for another sibling */ } @ drivers/gpu/drm/i915/gt/intel_execlists_submission.c:1594 @ static void execlists_dequeue(struct intel_engine_cs *engine) */ sched_engine->queue_priority_hint = queue_prio(sched_engine); i915_sched_engine_reset_on_empty(sched_engine); - spin_unlock(&sched_engine->lock); + spin_unlock_irq(&sched_engine->lock); /* * We can skip poking the HW if we ended up with exactly the same set @ drivers/gpu/drm/i915/gt/intel_execlists_submission.c:1620 @ static void execlists_dequeue(struct intel_engine_cs *engine) } } -static void execlists_dequeue_irq(struct intel_engine_cs *engine) -{ - local_irq_disable(); /* Suspend interrupts across request submission */ - execlists_dequeue(engine); - local_irq_enable(); /* flush irq_work (e.g. breadcrumb enabling) */ -} - static void clear_ports(struct i915_request **ports, int count) { memset_p((void **)ports, NULL, count); @ drivers/gpu/drm/i915/gt/intel_execlists_submission.c:2474 @ static void execlists_submission_tasklet(struct tasklet_struct *t) } if (!engine->execlists.pending[0]) { - execlists_dequeue_irq(engine); + execlists_dequeue(engine); start_timeslice(engine); } @ drivers/gpu/drm/i915/gt/uc/intel_guc.h:363 @ static inline int intel_guc_send_busy_loop(struct intel_guc *guc, { int err; unsigned int sleep_period_ms = 1; - bool not_atomic = !in_atomic() && !irqs_disabled(); + bool not_atomic = !in_atomic() && !irqs_disabled() && !rcu_preempt_depth(); /* * FIXME: Have caller pass in if we are in an atomic context to avoid @ drivers/gpu/drm/i915/i915_request.c:611 @ bool __i915_request_submit(struct i915_request *request) RQ_TRACE(request, "\n"); - GEM_BUG_ON(!irqs_disabled()); lockdep_assert_held(&engine->sched_engine->lock); /* @ drivers/gpu/drm/i915/i915_request.c:719 @ void __i915_request_unsubmit(struct i915_request *request) */ RQ_TRACE(request, "\n"); - GEM_BUG_ON(!irqs_disabled()); lockdep_assert_held(&engine->sched_engine->lock); /* @ drivers/gpu/drm/i915/i915_trace.h:9 @ #if !defined(_I915_TRACE_H_) || defined(TRACE_HEADER_MULTI_READ) #define _I915_TRACE_H_ +#ifdef CONFIG_PREEMPT_RT +#define NOTRACE +#endif + #include <linux/stringify.h> #include <linux/types.h> #include <linux/tracepoint.h> @ drivers/gpu/drm/i915/i915_trace.h:329 @ DEFINE_EVENT(i915_request, i915_request_add, TP_ARGS(rq) ); -#if defined(CONFIG_DRM_I915_LOW_LEVEL_TRACEPOINTS) +#if defined(CONFIG_DRM_I915_LOW_LEVEL_TRACEPOINTS) && !defined(NOTRACE) DEFINE_EVENT(i915_request, i915_request_guc_submit, TP_PROTO(struct i915_request *rq), TP_ARGS(rq) @ drivers/gpu/drm/i915/i915_utils.h:291 @ wait_remaining_ms_from_jiffies(unsigned long timestamp_jiffies, int to_wait_ms) #define wait_for(COND, MS) _wait_for((COND), (MS) * 1000, 10, 1000) /* If CONFIG_PREEMPT_COUNT is disabled, in_atomic() always reports false. */ -#if defined(CONFIG_DRM_I915_DEBUG) && defined(CONFIG_PREEMPT_COUNT) +#if defined(CONFIG_DRM_I915_DEBUG) && defined(CONFIG_PREEMPT_COUNT) && !defined(CONFIG_PREEMPT_RT) # define _WAIT_FOR_ATOMIC_CHECK(ATOMIC) WARN_ON_ONCE((ATOMIC) && !in_atomic()) #else # define _WAIT_FOR_ATOMIC_CHECK(ATOMIC) do { } while (0) @ drivers/gpu/drm/ttm/tests/ttm_bo_test.c:21 @ #define BO_SIZE SZ_8K +#ifdef CONFIG_PREEMPT_RT +#define ww_mutex_base_lock(b) rt_mutex_lock(b) +#else +#define ww_mutex_base_lock(b) mutex_lock(b) +#endif + struct ttm_bo_test_case { const char *description; bool interruptible; @ drivers/gpu/drm/ttm/tests/ttm_bo_test.c:151 @ static void ttm_bo_reserve_deadlock(struct kunit *test) bo2 = ttm_bo_kunit_init(test, test->priv, BO_SIZE); ww_acquire_init(&ctx1, &reservation_ww_class); - mutex_lock(&bo2->base.resv->lock.base); + ww_mutex_base_lock(&bo2->base.resv->lock.base); /* The deadlock will be caught by WW mutex, don't warn about it */ lock_release(&bo2->base.resv->lock.base.dep_map, 1); @ drivers/tty/serial/8250/8250_core.c:595 @ serial8250_register_ports(struct uart_driver *drv, struct device *dev) #ifdef CONFIG_SERIAL_8250_CONSOLE +#ifdef CONFIG_SERIAL_8250_LEGACY_CONSOLE static void univ8250_console_write(struct console *co, const char *s, unsigned int count) { @ drivers/tty/serial/8250/8250_core.c:603 @ static void univ8250_console_write(struct console *co, const char *s, serial8250_console_write(up, s, count); } +#else +static void univ8250_console_write_atomic(struct console *co, + struct nbcon_write_context *wctxt) +{ + struct uart_8250_port *up = &serial8250_ports[co->index]; + + serial8250_console_write_atomic(up, wctxt); +} + +static void univ8250_console_write_thread(struct console *co, + struct nbcon_write_context *wctxt) +{ + struct uart_8250_port *up = &serial8250_ports[co->index]; + + serial8250_console_write_thread(up, wctxt); +} + +static void univ8250_console_device_lock(struct console *con, unsigned long *flags) +{ + struct uart_port *up = &serial8250_ports[con->index].port; + + __uart_port_lock_irqsave(up, flags); +} + +static void univ8250_console_device_unlock(struct console *con, unsigned long flags) +{ + struct uart_port *up = &serial8250_ports[con->index].port; + + __uart_port_unlock_irqrestore(up, flags); +} + +static struct nbcon_drvdata serial8250_nbcon_drvdata; +#endif /* CONFIG_SERIAL_8250_LEGACY_CONSOLE */ static int univ8250_console_setup(struct console *co, char *options) { @ drivers/tty/serial/8250/8250_core.c:664 @ static int univ8250_console_setup(struct console *co, char *options) port = &serial8250_ports[co->index].port; /* link port to console */ - port->cons = co; + uart_port_set_cons(port, co); retval = serial8250_console_setup(port, options, false); if (retval != 0) - port->cons = NULL; + uart_port_set_cons(port, NULL); return retval; } @ drivers/tty/serial/8250/8250_core.c:726 @ static int univ8250_console_match(struct console *co, char *name, int idx, continue; co->index = i; - port->cons = co; + uart_port_set_cons(port, co); return serial8250_console_setup(port, options, true); } @ drivers/tty/serial/8250/8250_core.c:735 @ static int univ8250_console_match(struct console *co, char *name, int idx, static struct console univ8250_console = { .name = "ttyS", +#ifdef CONFIG_SERIAL_8250_LEGACY_CONSOLE .write = univ8250_console_write, + .flags = CON_PRINTBUFFER | CON_ANYTIME, +#else + .write_atomic = univ8250_console_write_atomic, + .write_thread = univ8250_console_write_thread, + .device_lock = univ8250_console_device_lock, + .device_unlock = univ8250_console_device_unlock, + .flags = CON_PRINTBUFFER | CON_ANYTIME | CON_NBCON, + .nbcon_drvdata = &serial8250_nbcon_drvdata, +#endif .device = uart_console_device, .setup = univ8250_console_setup, .exit = univ8250_console_exit, .match = univ8250_console_match, - .flags = CON_PRINTBUFFER | CON_ANYTIME, .index = -1, .data = &serial8250_reg, }; @ drivers/tty/serial/8250/8250_port.c:549 @ static int serial8250_em485_init(struct uart_8250_port *p) if (!p->em485) return -ENOMEM; +#ifndef CONFIG_SERIAL_8250_LEGACY_CONSOLE + if (uart_console(&p->port)) { + dev_warn(p->port.dev, "no atomic printing for rs485 consoles\n"); + p->port.cons->write_atomic = NULL; + } +#endif + hrtimer_init(&p->em485->stop_tx_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); hrtimer_init(&p->em485->start_tx_timer, CLOCK_MONOTONIC, @ drivers/tty/serial/8250/8250_port.c:708 @ static void serial8250_set_sleep(struct uart_8250_port *p, int sleep) serial8250_rpm_put(p); } -static void serial8250_clear_IER(struct uart_8250_port *up) +/* + * Only to be used by write_atomic() and the legacy write(), which do not + * require port lock. + */ +static void __serial8250_clear_IER(struct uart_8250_port *up) { if (up->capabilities & UART_CAP_UUE) serial_out(up, UART_IER, UART_IER_UUE); @ drivers/tty/serial/8250/8250_port.c:720 @ static void serial8250_clear_IER(struct uart_8250_port *up) serial_out(up, UART_IER, 0); } +static inline void serial8250_clear_IER(struct uart_8250_port *up) +{ + /* Port locked to synchronize UART_IER access against the console. */ + lockdep_assert_held_once(&up->port.lock); + + __serial8250_clear_IER(up); +} + #ifdef CONFIG_SERIAL_8250_RSA /* * Attempts to turn on the RSA FIFO. Returns zero on failure. @ drivers/tty/serial/8250/8250_port.c:3294 @ static void serial8250_console_putchar(struct uart_port *port, unsigned char ch) wait_for_xmitr(up, UART_LSR_THRE); serial_port_out(port, UART_TX, ch); + + if (ch == '\n') + up->console_newline_needed = false; + else + up->console_newline_needed = true; } /* @ drivers/tty/serial/8250/8250_port.c:3327 @ static void serial8250_console_restore(struct uart_8250_port *up) serial8250_out_MCR(up, up->mcr | UART_MCR_DTR | UART_MCR_RTS); } +#ifdef CONFIG_SERIAL_8250_LEGACY_CONSOLE /* * Print a string to the serial port using the device FIFO * @ drivers/tty/serial/8250/8250_port.c:3386 @ void serial8250_console_write(struct uart_8250_port *up, const char *s, * First save the IER then disable the interrupts */ ier = serial_port_in(port, UART_IER); - serial8250_clear_IER(up); + __serial8250_clear_IER(up); /* check scratch reg to see if port powered off during system sleep */ if (up->canary && (up->canary != serial_port_in(port, UART_SCR))) { @ drivers/tty/serial/8250/8250_port.c:3452 @ void serial8250_console_write(struct uart_8250_port *up, const char *s, if (locked) uart_port_unlock_irqrestore(port, flags); } +#else +void serial8250_console_write_thread(struct uart_8250_port *up, + struct nbcon_write_context *wctxt) +{ + struct uart_8250_em485 *em485 = up->em485; + struct uart_port *port = &up->port; + unsigned int ier; + + touch_nmi_watchdog(); + + if (!nbcon_enter_unsafe(wctxt)) + return; + + /* First save IER then disable the interrupts. */ + ier = serial_port_in(port, UART_IER); + serial8250_clear_IER(up); + + /* Check scratch reg if port powered off during system sleep. */ + if (up->canary && (up->canary != serial_port_in(port, UART_SCR))) { + serial8250_console_restore(up); + up->canary = 0; + } + + if (em485) { + if (em485->tx_stopped) + up->rs485_start_tx(up); + mdelay(port->rs485.delay_rts_before_send); + } + + if (nbcon_exit_unsafe(wctxt)) { + int len = READ_ONCE(wctxt->len); + int i; + + /* + * Write out the message. Toggle unsafe for each byte in order + * to give another (higher priority) context the opportunity + * for a friendly takeover. If such a takeover occurs, this + * context must reacquire ownership in order to perform final + * actions (such as re-enabling the interrupts). + * + * IMPORTANT: wctxt->outbuf and wctxt->len are no longer valid + * after a reacquire so writing the message must be + * aborted. + */ + for (i = 0; i < len; i++) { + if (!nbcon_enter_unsafe(wctxt)) { + nbcon_reacquire(wctxt); + break; + } + + uart_console_write(port, wctxt->outbuf + i, 1, serial8250_console_putchar); + + if (!nbcon_exit_unsafe(wctxt)) { + nbcon_reacquire(wctxt); + break; + } + } + } else { + nbcon_reacquire(wctxt); + } + + while (!nbcon_enter_unsafe(wctxt)) + nbcon_reacquire(wctxt); + + /* Finally, wait for transmitter to become empty and restore IER. */ + wait_for_xmitr(up, UART_LSR_BOTH_EMPTY); + if (em485) { + mdelay(port->rs485.delay_rts_after_send); + if (em485->tx_stopped) + up->rs485_stop_tx(up); + } + serial_port_out(port, UART_IER, ier); + + /* + * The receive handling will happen properly because the receive ready + * bit will still be set; it is not cleared on read. However, modem + * control will not, we must call it if we have saved something in the + * saved flags while processing with interrupts off. + */ + if (up->msr_saved_flags) + serial8250_modem_status(up); + + nbcon_exit_unsafe(wctxt); +} + +void serial8250_console_write_atomic(struct uart_8250_port *up, + struct nbcon_write_context *wctxt) +{ + struct uart_port *port = &up->port; + unsigned int ier; + + /* Atomic console not supported for rs485 mode. */ + if (WARN_ON_ONCE(up->em485)) + return; + + touch_nmi_watchdog(); + + if (!nbcon_enter_unsafe(wctxt)) + return; + + /* + * First save IER then disable the interrupts. The special variant to + * clear IER is used because atomic printing may occur without holding + * the port lock. + */ + ier = serial_port_in(port, UART_IER); + __serial8250_clear_IER(up); + + /* Check scratch reg if port powered off during system sleep. */ + if (up->canary && (up->canary != serial_port_in(port, UART_SCR))) { + serial8250_console_restore(up); + up->canary = 0; + } + + if (up->console_newline_needed) + uart_console_write(port, "\n", 1, serial8250_console_putchar); + uart_console_write(port, wctxt->outbuf, wctxt->len, serial8250_console_putchar); + + /* Finally, wait for transmitter to become empty and restore IER. */ + wait_for_xmitr(up, UART_LSR_BOTH_EMPTY); + serial_port_out(port, UART_IER, ier); + + nbcon_exit_unsafe(wctxt); +} +#endif /* CONFIG_SERIAL_8250_LEGACY_CONSOLE */ static unsigned int probe_baud(struct uart_port *port) { @ drivers/tty/serial/8250/8250_port.c:3595 @ static unsigned int probe_baud(struct uart_port *port) int serial8250_console_setup(struct uart_port *port, char *options, bool probe) { + struct uart_8250_port *up = up_to_u8250p(port); int baud = 9600; int bits = 8; int parity = 'n'; @ drivers/tty/serial/8250/8250_port.c:3605 @ int serial8250_console_setup(struct uart_port *port, char *options, bool probe) if (!port->iobase && !port->membase) return -ENODEV; + up->console_newline_needed = false; + if (options) uart_parse_options(options, &baud, &parity, &bits, &flow); else if (probe) @ drivers/tty/serial/amba-pl011.c:2491 @ static int pl011_console_match(struct console *co, char *name, int idx, continue; co->index = i; - port->cons = co; + uart_port_set_cons(port, co); return pl011_console_setup(co, options); } @ drivers/tty/serial/serial_core.c:3160 @ static int serial_core_add_one_port(struct uart_driver *drv, struct uart_port *u state->uart_port = uport; uport->state = state; + /* + * If this port is in use as a console then the spinlock is already + * initialised. + */ + if (!uart_console_registered(uport)) + uart_port_spin_lock_init(uport); + state->pm_state = UART_PM_STATE_UNDEFINED; - uport->cons = drv->cons; + uart_port_set_cons(uport, drv->cons); uport->minor = drv->tty_driver->minor_start + uport->line; uport->name = kasprintf(GFP_KERNEL, "%s%d", drv->dev_name, drv->tty_driver->name_base + uport->line); @ drivers/tty/serial/serial_core.c:3177 @ static int serial_core_add_one_port(struct uart_driver *drv, struct uart_port *u goto out; } - /* - * If this port is in use as a console then the spinlock is already - * initialised. - */ - if (!uart_console_registered(uport)) - uart_port_spin_lock_init(uport); - if (uport->cons && uport->dev) of_console_check(uport->dev->of_node, uport->cons->name, uport->line); @ drivers/tty/tty_io.c:3570 @ static ssize_t show_cons_active(struct device *dev, for_each_console(c) { if (!c->device) continue; - if (!c->write) - continue; + if (c->flags & CON_NBCON) { + if (!c->write_atomic && !c->write_thread) + continue; + } else { + if (!c->write) + continue; + } if ((c->flags & CON_ENABLED) == 0) continue; cs[i++] = c; @ fs/proc/consoles.c:24 @ static int show_console_dev(struct seq_file *m, void *v) { CON_ENABLED, 'E' }, { CON_CONSDEV, 'C' }, { CON_BOOT, 'B' }, + { CON_NBCON, 'N' }, { CON_PRINTBUFFER, 'p' }, { CON_BRL, 'b' }, { CON_ANYTIME, 'a' }, }; char flags[ARRAY_SIZE(con_flags) + 1]; struct console *con = v; + char con_write = '-'; unsigned int a; dev_t dev = 0; @ fs/proc/consoles.c:62 @ static int show_console_dev(struct seq_file *m, void *v) seq_setwidth(m, 21 - 1); seq_printf(m, "%s%d", con->name, con->index); seq_pad(m, ' '); - seq_printf(m, "%c%c%c (%s)", con->read ? 'R' : '-', - con->write ? 'W' : '-', con->unblank ? 'U' : '-', - flags); + if (con->flags & CON_NBCON) { + if (con->write_atomic || con->write_thread) + con_write = 'W'; + } else { + if (con->write) + con_write = 'W'; + } + seq_printf(m, "%c%c%c (%s)", con->read ? 'R' : '-', con_write, + con->unblank ? 'U' : '-', flags); if (dev) seq_printf(m, " %4d:%d", MAJOR(dev), MINOR(dev)); @ include/linux/bottom_half.h:38 @ static inline void local_bh_enable(void) #ifdef CONFIG_PREEMPT_RT extern bool local_bh_blocked(void); +extern void softirq_preempt(void); #else static inline bool local_bh_blocked(void) { return false; } +static inline void softirq_preempt(void) { } #endif #endif /* _LINUX_BH_H */ @ include/linux/console.h:19 @ #include <linux/atomic.h> #include <linux/bits.h> +#include <linux/irq_work.h> #include <linux/rculist.h> +#include <linux/rcuwait.h> #include <linux/types.h> #include <linux/vesa.h> @ include/linux/console.h:305 @ struct nbcon_write_context { bool unsafe_takeover; }; +/** + * struct nbcon_drvdata - Data to allow nbcon acquire in non-print context + * @ctxt: The core console context + * @srcu_cookie: Storage for a console_srcu_lock cookie, if needed + * @owner_index: Storage for the owning console index, if needed + * @locked: Storage for the locked state, if needed + * + * All fields (except for @ctxt) are available exclusively to the driver to + * use as needed. They are not used by the printk subsystem. + */ +struct nbcon_drvdata { + struct nbcon_context __private ctxt; + + /* reserved for driver use */ + int srcu_cookie; + short owner_index; + bool locked; +}; + /** * struct console - The console descriptor structure * @name: The name of the console driver - * @write: Write callback to output messages (Optional) + * @write: Legacy write callback to output messages (Optional) * @read: Read callback for console input (Optional) * @device: The underlying TTY device driver (Optional) * @unblank: Callback to unblank the console (Optional) @ include/linux/console.h:344 @ struct nbcon_write_context { * @data: Driver private data * @node: hlist node for the console list * - * @write_atomic: Write callback for atomic context * @nbcon_state: State for nbcon consoles * @nbcon_seq: Sequence number of the next record for nbcon to print + * @nbcon_prev_seq: Seq num the previous nbcon owner was assigned to print * @pbufs: Pointer to nbcon private buffer + * @kthread: Printer kthread for this console + * @rcuwait: RCU-safe wait object for @kthread waking + * @irq_work: Defer @kthread waking to IRQ work context */ struct console { char name[16]; @ include/linux/console.h:372 @ struct console { struct hlist_node node; /* nbcon console specific members */ - bool (*write_atomic)(struct console *con, - struct nbcon_write_context *wctxt); + + /** + * @write_atomic: + * + * NBCON callback to write out text in any context. + * + * This callback is called with the console already acquired. The + * callback can use nbcon_can_proceed() at any time to verify that + * it is still the owner of the console. In the case that it has + * lost ownership, it is no longer allowed to go forward. In this + * case it must back out immediately and carefully. The buffer + * content is also no longer trusted since it no longer belongs to + * the context. + * + * If the callback needs to perform actions where ownership is not + * allowed to be taken over, nbcon_enter_unsafe() and + * nbcon_exit_unsafe() can be used to mark such sections. These + * functions are also points of possible ownership transfer. If + * either function returns false, ownership has been lost. + * + * If the driver must reacquire ownership in order to finalize or + * revert hardware changes, nbcon_reacquire() can be used. However, + * on reacquire the buffer content is no longer available. A + * reacquire cannot be used to resume printing. + * + * This callback can be called from any context (including NMI). + * Therefore it must avoid usage of any locking and instead rely + * on the console ownership for synchronization. + */ + void (*write_atomic)(struct console *con, struct nbcon_write_context *wctxt); + + /** + * @write_thread: + * + * NBCON callback to write out text in task context. (Optional) + * + * This callback is called with the console already acquired. Any + * additional driver synchronization should have been performed by + * device_lock(). + * + * This callback is always called from task context but with migration + * disabled. + * + * The same criteria for console ownership verification and unsafe + * sections applies as with write_atomic(). The difference between + * this callback and write_atomic() is that this callback is used + * during normal operation and is always called from task context. + * This provides drivers with a relatively relaxed locking context + * for synchronizing output to the hardware. + */ + void (*write_thread)(struct console *con, struct nbcon_write_context *wctxt); + + /** + * @device_lock: + * + * NBCON callback to begin synchronization with driver code. + * + * Console drivers typically must deal with access to the hardware + * via user input/output (such as an interactive login shell) and + * output of kernel messages via printk() calls. This callback is + * called by the printk-subsystem whenever it needs to synchronize + * with hardware access by the driver. It should be implemented to + * use whatever synchronization mechanism the driver is using for + * itself (for example, the port lock for uart serial consoles). + * + * This callback is always called from task context. It may use any + * synchronization method required by the driver. BUT this callback + * MUST also disable migration. The console driver may be using a + * synchronization mechanism that already takes care of this (such as + * spinlocks). Otherwise this function must explicitly call + * migrate_disable(). + * + * The flags argument is provided as a convenience to the driver. It + * will be passed again to device_unlock(). It can be ignored if the + * driver does not need it. + */ + void (*device_lock)(struct console *con, unsigned long *flags); + + /** + * @device_unlock: + * + * NBCON callback to finish synchronization with driver code. + * + * It is the counterpart to device_lock(). + * + * This callback is always called from task context. It must + * appropriately re-enable migration (depending on how device_lock() + * disabled migration). + * + * The flags argument is the value of the same variable that was + * passed to device_lock(). + */ + void (*device_unlock)(struct console *con, unsigned long flags); + atomic_t __private nbcon_state; atomic_long_t __private nbcon_seq; + atomic_long_t __private nbcon_prev_seq; + + /** + * @nbcon_drvdata: + * + * Data for nbcon ownership tracking to allow acquiring nbcon consoles + * in non-printing contexts. + * + * Drivers may need to acquire nbcon consoles in non-printing + * contexts. This is achieved by providing a struct nbcon_drvdata. + * Then the driver can call nbcon_driver_acquire() and + * nbcon_driver_release(). The struct does not require any special + * initialization. + */ + struct nbcon_drvdata *nbcon_drvdata; + struct printk_buffers *pbufs; + struct task_struct *kthread; + struct rcuwait rcuwait; + struct irq_work irq_work; }; #ifdef CONFIG_LOCKDEP @ include/linux/console.h:516 @ extern void console_list_unlock(void) __releases(console_mutex); extern struct hlist_head console_list; /** - * console_srcu_read_flags - Locklessly read the console flags + * console_srcu_read_flags - Locklessly read flags of a possibly registered + * console * @con: struct console pointer of console to read flags from * - * This function provides the necessary READ_ONCE() and data_race() - * notation for locklessly reading the console flags. The READ_ONCE() - * in this function matches the WRITE_ONCE() when @flags are modified - * for registered consoles with console_srcu_write_flags(). + * Locklessly reading @con->flags provides a consistent read value because + * there is at most one CPU modifying @con->flags and that CPU is using only + * read-modify-write operations to do so. * - * Only use this function to read console flags when locklessly - * iterating the console list via srcu. + * Requires console_srcu_read_lock to be held, which implies that @con might + * be a registered console. If the caller is holding the console_list_lock or + * it is certain that the console is not registered, the caller may read + * @con->flags directly instead. * * Context: Any context. + * Return: The current value of the @con->flags field. */ static inline short console_srcu_read_flags(const struct console *con) { WARN_ON_ONCE(!console_srcu_read_lock_is_held()); /* - * Locklessly reading console->flags provides a consistent - * read value because there is at most one CPU modifying - * console->flags and that CPU is using only read-modify-write - * operations to do so. + * The READ_ONCE() matches the WRITE_ONCE() when @flags are modified + * for registered consoles with console_srcu_write_flags(). */ return data_race(READ_ONCE(con->flags)); } @ include/linux/console.h:616 @ static inline bool console_is_registered(const struct console *con) hlist_for_each_entry(con, &console_list, node) #ifdef CONFIG_PRINTK +extern void nbcon_cpu_emergency_enter(void); +extern void nbcon_cpu_emergency_exit(void); extern bool nbcon_can_proceed(struct nbcon_write_context *wctxt); extern bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt); extern bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt); +extern void nbcon_reacquire(struct nbcon_write_context *wctxt); #else +static inline void nbcon_cpu_emergency_enter(void) { } +static inline void nbcon_cpu_emergency_exit(void) { } static inline bool nbcon_can_proceed(struct nbcon_write_context *wctxt) { return false; } static inline bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt) { return false; } static inline bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt) { return false; } +static inline void nbcon_reacquire(struct nbcon_write_context *wctxt) { } #endif extern int console_set_on_cmdline; @ include/linux/entry-common.h:68 @ #define EXIT_TO_USER_MODE_WORK \ (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE | \ _TIF_NEED_RESCHED | _TIF_PATCH_PENDING | _TIF_NOTIFY_SIGNAL | \ - ARCH_EXIT_TO_USER_MODE_WORK) + _TIF_NEED_RESCHED_LAZY | ARCH_EXIT_TO_USER_MODE_WORK) /** * arch_enter_from_user_mode - Architecture specific sanity check for user mode regs @ include/linux/entry-kvm.h:21 @ #define XFER_TO_GUEST_MODE_WORK \ (_TIF_NEED_RESCHED | _TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL | \ - _TIF_NOTIFY_RESUME | ARCH_XFER_TO_GUEST_MODE_WORK) + _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED_LAZY | ARCH_XFER_TO_GUEST_MODE_WORK) struct kvm_vcpu; @ include/linux/interrupt.h:615 @ extern void __raise_softirq_irqoff(unsigned int nr); extern void raise_softirq_irqoff(unsigned int nr); extern void raise_softirq(unsigned int nr); +#ifdef CONFIG_PREEMPT_RT +DECLARE_PER_CPU(struct task_struct *, timersd); +DECLARE_PER_CPU(unsigned long, pending_timer_softirq); + +extern void raise_timer_softirq(void); +extern void raise_hrtimer_softirq(void); + +static inline unsigned int local_pending_timers(void) +{ + return __this_cpu_read(pending_timer_softirq); +} + +#else +static inline void raise_timer_softirq(void) +{ + raise_softirq(TIMER_SOFTIRQ); +} + +static inline void raise_hrtimer_softirq(void) +{ + raise_softirq_irqoff(HRTIMER_SOFTIRQ); +} + +static inline unsigned int local_pending_timers(void) +{ + return local_softirq_pending(); +} +#endif + DECLARE_PER_CPU(struct task_struct *, ksoftirqd); static inline struct task_struct *this_cpu_ksoftirqd(void) @ include/linux/netdevice.h:3290 @ static inline void dev_xmit_recursion_dec(void) __this_cpu_dec(softnet_data.xmit.recursion); } +void kick_defer_list_purge(struct softnet_data *sd, unsigned int cpu); void __netif_schedule(struct Qdisc *q); void netif_schedule_queue(struct netdev_queue *txq); @ include/linux/perf_event.h:784 @ struct perf_event { unsigned int pending_wakeup; unsigned int pending_kill; unsigned int pending_disable; - unsigned int pending_sigtrap; unsigned long pending_addr; /* SIGTRAP */ struct irq_work pending_irq; + struct irq_work pending_disable_irq; struct callback_head pending_task; unsigned int pending_work; @ include/linux/perf_event.h:962 @ struct perf_event_context { struct rcu_head rcu_head; /* - * Sum (event->pending_sigtrap + event->pending_work) + * Sum (event->pending_work + event->pending_work) * * The SIGTRAP is targeted at ctx->task, as such it won't do changing * that until the signal is delivered. @ include/linux/printk.h:12 @ #include <linux/ratelimit_types.h> #include <linux/once_lite.h> +struct console; + extern const char linux_banner[]; extern const char linux_proc_banner[]; @ include/linux/printk.h:162 @ int _printk(const char *fmt, ...); */ __printf(1, 2) __cold int _printk_deferred(const char *fmt, ...); -extern void __printk_safe_enter(void); -extern void __printk_safe_exit(void); +extern void __printk_deferred_enter(void); +extern void __printk_deferred_exit(void); + /* * The printk_deferred_enter/exit macros are available only as a hack for * some code paths that need to defer all printk console printing. Interrupts * must be disabled for the deferred duration. */ -#define printk_deferred_enter __printk_safe_enter -#define printk_deferred_exit __printk_safe_exit +#define printk_deferred_enter() __printk_deferred_enter() +#define printk_deferred_exit() __printk_deferred_exit() /* * Please don't use printk_ratelimit(), because it shares ratelimiting state @ include/linux/printk.h:198 @ void show_regs_print_info(const char *log_lvl); extern asmlinkage void dump_stack_lvl(const char *log_lvl) __cold; extern asmlinkage void dump_stack(void) __cold; void printk_trigger_flush(void); +void printk_legacy_allow_panic_sync(void); +extern void nbcon_driver_acquire(struct console *con); +extern void nbcon_driver_release(struct console *con); +void nbcon_atomic_flush_unsafe(void); #else static inline __printf(1, 0) int vprintk(const char *s, va_list args) @ include/linux/printk.h:281 @ static inline void dump_stack(void) static inline void printk_trigger_flush(void) { } + +static inline void printk_legacy_allow_panic_sync(void) +{ +} + +static inline void nbcon_driver_acquire(struct console *con) +{ +} + +static inline void nbcon_driver_release(struct console *con) +{ +} + +static inline void nbcon_atomic_flush_unsafe(void) +{ +} + #endif bool this_cpu_in_panic(void); @ include/linux/rwbase_rt.h:34 @ static __always_inline bool rw_base_is_locked(const struct rwbase_rt *rwb) return atomic_read(&rwb->readers) != READER_BIAS; } -static inline void rw_base_assert_held_write(const struct rwbase_rt *rwb) +static __always_inline bool rw_base_is_write_locked(const struct rwbase_rt *rwb) { - WARN_ON(atomic_read(&rwb->readers) != WRITER_BIAS); + return atomic_read(&rwb->readers) == WRITER_BIAS; } static __always_inline bool rw_base_is_contended(const struct rwbase_rt *rwb) @ include/linux/rwsem.h:170 @ static __always_inline int rwsem_is_locked(const struct rw_semaphore *sem) return rw_base_is_locked(&sem->rwbase); } -static inline void rwsem_assert_held_nolockdep(const struct rw_semaphore *sem) +static __always_inline void rwsem_assert_held_nolockdep(const struct rw_semaphore *sem) { WARN_ON(!rwsem_is_locked(sem)); } -static inline void rwsem_assert_held_write_nolockdep(const struct rw_semaphore *sem) +static __always_inline void rwsem_assert_held_write_nolockdep(const struct rw_semaphore *sem) { - rw_base_assert_held_write(sem); + WARN_ON(!rw_base_is_write_locked(&sem->rwbase)); } static __always_inline int rwsem_is_contended(struct rw_semaphore *sem) @ include/linux/sched.h:1798 @ static inline int dl_task_check_affinity(struct task_struct *p, const struct cpu } #endif +extern bool task_is_pi_boosted(const struct task_struct *p); extern int yield_to(struct task_struct *p, bool preempt); extern void set_user_nice(struct task_struct *p, long nice); extern int task_prio(const struct task_struct *p); @ include/linux/sched.h:1941 @ static inline void update_tsk_thread_flag(struct task_struct *tsk, int flag, update_ti_thread_flag(task_thread_info(tsk), flag, value); } -static inline int test_and_set_tsk_thread_flag(struct task_struct *tsk, int flag) +static inline bool test_and_set_tsk_thread_flag(struct task_struct *tsk, int flag) { return test_and_set_ti_thread_flag(task_thread_info(tsk), flag); } -static inline int test_and_clear_tsk_thread_flag(struct task_struct *tsk, int flag) +static inline bool test_and_clear_tsk_thread_flag(struct task_struct *tsk, int flag) { return test_and_clear_ti_thread_flag(task_thread_info(tsk), flag); } -static inline int test_tsk_thread_flag(struct task_struct *tsk, int flag) +static inline bool test_tsk_thread_flag(struct task_struct *tsk, int flag) { return test_ti_thread_flag(task_thread_info(tsk), flag); } @ include/linux/sched.h:1964 @ static inline void set_tsk_need_resched(struct task_struct *tsk) static inline void clear_tsk_need_resched(struct task_struct *tsk) { clear_tsk_thread_flag(tsk,TIF_NEED_RESCHED); + if (IS_ENABLED(CONFIG_PREEMPT_BUILD_AUTO)) + clear_tsk_thread_flag(tsk, TIF_NEED_RESCHED_LAZY); } -static inline int test_tsk_need_resched(struct task_struct *tsk) +static inline bool test_tsk_need_resched(struct task_struct *tsk) { return unlikely(test_tsk_thread_flag(tsk,TIF_NEED_RESCHED)); } @ include/linux/sched.h:2109 @ static inline bool preempt_model_preemptible(void) static __always_inline bool need_resched(void) { - return unlikely(tif_need_resched()); + return unlikely(tif_need_resched_lazy() || tif_need_resched()); } /* @ include/linux/sched/idle.h:66 @ static __always_inline bool __must_check current_set_polling_and_test(void) */ smp_mb__after_atomic(); - return unlikely(tif_need_resched()); + return unlikely(need_resched()); } static __always_inline bool __must_check current_clr_polling_and_test(void) @ include/linux/sched/idle.h:79 @ static __always_inline bool __must_check current_clr_polling_and_test(void) */ smp_mb__after_atomic(); - return unlikely(tif_need_resched()); + return unlikely(need_resched()); } #else @ include/linux/sched/idle.h:88 @ static inline void __current_clr_polling(void) { } static inline bool __must_check current_set_polling_and_test(void) { - return unlikely(tif_need_resched()); + return unlikely(need_resched()); } static inline bool __must_check current_clr_polling_and_test(void) { - return unlikely(tif_need_resched()); + return unlikely(need_resched()); } #endif @ include/linux/serial_8250.h:156 @ struct uart_8250_port { #define MSR_SAVE_FLAGS UART_MSR_ANY_DELTA unsigned char msr_saved_flags; + bool console_newline_needed; + struct uart_8250_dma *dma; const struct uart_8250_ops *ops; @ include/linux/serial_8250.h:209 @ void serial8250_init_port(struct uart_8250_port *up); void serial8250_set_defaults(struct uart_8250_port *up); void serial8250_console_write(struct uart_8250_port *up, const char *s, unsigned int count); +void serial8250_console_write_atomic(struct uart_8250_port *up, + struct nbcon_write_context *wctxt); +void serial8250_console_write_thread(struct uart_8250_port *up, + struct nbcon_write_context *wctxt); int serial8250_console_setup(struct uart_port *port, char *options, bool probe); int serial8250_console_exit(struct uart_port *port); @ include/linux/serial_core.h:11 @ #define LINUX_SERIAL_CORE_H #include <linux/bitops.h> +#include <linux/bug.h> #include <linux/compiler.h> #include <linux/console.h> #include <linux/interrupt.h> #include <linux/circ_buf.h> +#include <linux/lockdep.h> +#include <linux/printk.h> #include <linux/spinlock.h> #include <linux/sched.h> #include <linux/tty.h> @ include/linux/serial_core.h:597 @ struct uart_port { void *private_data; /* generic platform data pointer */ }; +/* + * Only for console->device_lock()/_unlock() callbacks and internal + * port lock wrapper synchronization. + */ +static inline void __uart_port_lock_irqsave(struct uart_port *up, unsigned long *flags) +{ + spin_lock_irqsave(&up->lock, *flags); +} + +/* + * Only for console->device_lock()/_unlock() callbacks and internal + * port lock wrapper synchronization. + */ +static inline void __uart_port_unlock_irqrestore(struct uart_port *up, unsigned long flags) +{ + spin_unlock_irqrestore(&up->lock, flags); +} + +/** + * uart_port_set_cons - Safely set the @cons field for a uart + * @up: The uart port to set + * @con: The new console to set to + * + * This function must be used to set @up->cons. It uses the port lock to + * synchronize with the port lock wrappers in order to ensure that the console + * cannot change or disappear while another context is holding the port lock. + */ +static inline void uart_port_set_cons(struct uart_port *up, struct console *con) +{ + unsigned long flags; + + __uart_port_lock_irqsave(up, &flags); + up->cons = con; + __uart_port_unlock_irqrestore(up, flags); +} + +/* Only for internal port lock wrapper usage. */ +static inline void __uart_port_nbcon_acquire(struct uart_port *up) +{ + lockdep_assert_held_once(&up->lock); + + if (likely(!uart_console(up))) + return; + + if (up->cons->nbcon_drvdata) { + /* + * If @up->cons is registered, prevent it from fully + * unregistering until this context releases the nbcon. + */ + int cookie = console_srcu_read_lock(); + + /* Ensure console is registered and is an nbcon console. */ + if (!hlist_unhashed_lockless(&up->cons->node) && + (console_srcu_read_flags(up->cons) & CON_NBCON)) { + WARN_ON_ONCE(up->cons->nbcon_drvdata->locked); + + nbcon_driver_acquire(up->cons); + + /* + * Record @up->line to be used during release because + * @up->cons->index can change while the port and + * nbcon are locked. + */ + up->cons->nbcon_drvdata->owner_index = up->line; + up->cons->nbcon_drvdata->srcu_cookie = cookie; + up->cons->nbcon_drvdata->locked = true; + } else { + console_srcu_read_unlock(cookie); + } + } +} + +/* Only for internal port lock wrapper usage. */ +static inline void __uart_port_nbcon_release(struct uart_port *up) +{ + lockdep_assert_held_once(&up->lock); + + /* + * uart_console() cannot be used here because @up->cons->index might + * have changed. Check against @up->cons->nbcon_drvdata->owner_index + * instead. + */ + + if (unlikely(up->cons && + up->cons->nbcon_drvdata && + up->cons->nbcon_drvdata->locked && + up->cons->nbcon_drvdata->owner_index == up->line)) { + WARN_ON_ONCE(!up->cons->nbcon_drvdata->locked); + + up->cons->nbcon_drvdata->locked = false; + nbcon_driver_release(up->cons); + console_srcu_read_unlock(up->cons->nbcon_drvdata->srcu_cookie); + } +} + /** * uart_port_lock - Lock the UART port * @up: Pointer to UART port structure @ include/linux/serial_core.h:699 @ struct uart_port { static inline void uart_port_lock(struct uart_port *up) { spin_lock(&up->lock); + __uart_port_nbcon_acquire(up); } /** @ include/linux/serial_core.h:709 @ static inline void uart_port_lock(struct uart_port *up) static inline void uart_port_lock_irq(struct uart_port *up) { spin_lock_irq(&up->lock); + __uart_port_nbcon_acquire(up); } /** @ include/linux/serial_core.h:720 @ static inline void uart_port_lock_irq(struct uart_port *up) static inline void uart_port_lock_irqsave(struct uart_port *up, unsigned long *flags) { spin_lock_irqsave(&up->lock, *flags); + __uart_port_nbcon_acquire(up); } /** @ include/linux/serial_core.h:731 @ static inline void uart_port_lock_irqsave(struct uart_port *up, unsigned long *f */ static inline bool uart_port_trylock(struct uart_port *up) { - return spin_trylock(&up->lock); + if (!spin_trylock(&up->lock)) + return false; + + __uart_port_nbcon_acquire(up); + return true; } /** @ include/linux/serial_core.h:747 @ static inline bool uart_port_trylock(struct uart_port *up) */ static inline bool uart_port_trylock_irqsave(struct uart_port *up, unsigned long *flags) { - return spin_trylock_irqsave(&up->lock, *flags); + if (!spin_trylock_irqsave(&up->lock, *flags)) + return false; + + __uart_port_nbcon_acquire(up); + return true; } /** @ include/linux/serial_core.h:760 @ static inline bool uart_port_trylock_irqsave(struct uart_port *up, unsigned long */ static inline void uart_port_unlock(struct uart_port *up) { + __uart_port_nbcon_release(up); spin_unlock(&up->lock); } @ include/linux/serial_core.h:770 @ static inline void uart_port_unlock(struct uart_port *up) */ static inline void uart_port_unlock_irq(struct uart_port *up) { + __uart_port_nbcon_release(up); spin_unlock_irq(&up->lock); } @ include/linux/serial_core.h:781 @ static inline void uart_port_unlock_irq(struct uart_port *up) */ static inline void uart_port_unlock_irqrestore(struct uart_port *up, unsigned long flags) { + __uart_port_nbcon_release(up); spin_unlock_irqrestore(&up->lock, flags); } @ include/linux/thread_info.h:62 @ enum syscall_work_bit { #include <asm/thread_info.h> +#ifdef CONFIG_PREEMPT_BUILD_AUTO +# define TIF_NEED_RESCHED_LAZY TIF_ARCH_RESCHED_LAZY +# define _TIF_NEED_RESCHED_LAZY _TIF_ARCH_RESCHED_LAZY +# define TIF_NEED_RESCHED_LAZY_OFFSET (TIF_NEED_RESCHED_LAZY - TIF_NEED_RESCHED) +#else +# define TIF_NEED_RESCHED_LAZY TIF_NEED_RESCHED +# define _TIF_NEED_RESCHED_LAZY _TIF_NEED_RESCHED +# define TIF_NEED_RESCHED_LAZY_OFFSET 0 +#endif + #ifdef __KERNEL__ #ifndef arch_set_restart_data @ include/linux/thread_info.h:198 @ static __always_inline bool tif_need_resched(void) (unsigned long *)(¤t_thread_info()->flags)); } +static __always_inline bool tif_need_resched_lazy(void) +{ + return IS_ENABLED(CONFIG_PREEMPT_BUILD_AUTO) && + arch_test_bit(TIF_NEED_RESCHED_LAZY, + (unsigned long *)(¤t_thread_info()->flags)); +} + #else static __always_inline bool tif_need_resched(void) @ include/linux/thread_info.h:213 @ static __always_inline bool tif_need_resched(void) (unsigned long *)(¤t_thread_info()->flags)); } +static __always_inline bool tif_need_resched_lazy(void) +{ + return IS_ENABLED(CONFIG_PREEMPT_BUILD_AUTO) && + test_bit(TIF_NEED_RESCHED_LAZY, + (unsigned long *)(¤t_thread_info()->flags)); +} + #endif /* _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H */ #ifndef CONFIG_HAVE_ARCH_WITHIN_STACK_FRAMES @ include/linux/trace_events.h:187 @ unsigned int tracing_gen_ctx_irq_test(unsigned int irqs_status); enum trace_flag_type { TRACE_FLAG_IRQS_OFF = 0x01, - TRACE_FLAG_IRQS_NOSUPPORT = 0x02, - TRACE_FLAG_NEED_RESCHED = 0x04, + TRACE_FLAG_NEED_RESCHED = 0x02, + TRACE_FLAG_NEED_RESCHED_LAZY = 0x04, TRACE_FLAG_HARDIRQ = 0x08, TRACE_FLAG_SOFTIRQ = 0x10, TRACE_FLAG_PREEMPT_RESCHED = 0x20, @ include/linux/trace_events.h:214 @ static inline unsigned int tracing_gen_ctx(void) static inline unsigned int tracing_gen_ctx_flags(unsigned long irqflags) { - return tracing_gen_ctx_irq_test(TRACE_FLAG_IRQS_NOSUPPORT); + return tracing_gen_ctx_irq_test(0); } static inline unsigned int tracing_gen_ctx(void) { - return tracing_gen_ctx_irq_test(TRACE_FLAG_IRQS_NOSUPPORT); + return tracing_gen_ctx_irq_test(0); } #endif @ kernel/Kconfig.preempt:14 @ config PREEMPT_BUILD select PREEMPTION select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK +config PREEMPT_BUILD_AUTO + bool + select PREEMPT_BUILD + +config HAVE_PREEMPT_AUTO + bool + choice prompt "Preemption Model" default PREEMPT_NONE @ kernel/Kconfig.preempt:77 @ config PREEMPT embedded system with latency requirements in the milliseconds range. +config PREEMPT_AUTO + bool "Automagic preemption mode with runtime tweaking support" + depends on HAVE_PREEMPT_AUTO + select PREEMPT_BUILD_AUTO + help + Add some sensible blurb here + config PREEMPT_RT bool "Fully Preemptible Kernel (Real-Time)" depends on EXPERT && ARCH_SUPPORTS_RT + select PREEMPT_BUILD_AUTO if HAVE_PREEMPT_AUTO select PREEMPTION help This option turns the kernel into a real-time kernel by replacing @ kernel/Kconfig.preempt:113 @ config PREEMPTION config PREEMPT_DYNAMIC bool "Preemption behaviour defined on boot" - depends on HAVE_PREEMPT_DYNAMIC && !PREEMPT_RT + depends on HAVE_PREEMPT_DYNAMIC && !PREEMPT_RT && !PREEMPT_AUTO select JUMP_LABEL if HAVE_PREEMPT_DYNAMIC_KEY select PREEMPT_BUILD default y if HAVE_PREEMPT_DYNAMIC_CALL @ kernel/entry/common.c:101 @ __always_inline unsigned long exit_to_user_mode_loop(struct pt_regs *regs, local_irq_enable_exit_to_user(ti_work); - if (ti_work & _TIF_NEED_RESCHED) + if (ti_work & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)) schedule(); if (ti_work & _TIF_UPROBE) @ kernel/entry/common.c:310 @ void raw_irqentry_exit_cond_resched(void) rcu_irq_exit_check_preempt(); if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) WARN_ON_ONCE(!on_thread_stack()); - if (need_resched()) + if (test_tsk_need_resched(current)) preempt_schedule_irq(); } } @ kernel/entry/kvm.c:16 @ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work) return -EINTR; } - if (ti_work & _TIF_NEED_RESCHED) + if (ti_work & (_TIF_NEED_RESCHED | TIF_NEED_RESCHED_LAZY)) schedule(); if (ti_work & _TIF_NOTIFY_RESUME) @ kernel/events/core.c:2286 @ event_sched_out(struct perf_event *event, struct perf_event_context *ctx) state = PERF_EVENT_STATE_OFF; } - if (event->pending_sigtrap) { - bool dec = true; - - event->pending_sigtrap = 0; - if (state != PERF_EVENT_STATE_OFF && - !event->pending_work) { - event->pending_work = 1; - dec = false; - WARN_ON_ONCE(!atomic_long_inc_not_zero(&event->refcount)); - task_work_add(current, &event->pending_task, TWA_RESUME); - } - if (dec) - local_dec(&event->ctx->nr_pending); - } - perf_event_set_state(event, state); if (!is_software_event(event)) @ kernel/events/core.c:2452 @ static void __perf_event_disable(struct perf_event *event, * hold the top-level event's child_mutex, so any descendant that * goes to exit will block in perf_event_exit_event(). * - * When called from perf_pending_irq it's OK because event->ctx + * When called from perf_pending_disable it's OK because event->ctx * is the current context on this CPU and preemption is disabled, * hence we can't get into perf_event_task_sched_out for this context. */ @ kernel/events/core.c:2492 @ EXPORT_SYMBOL_GPL(perf_event_disable); void perf_event_disable_inatomic(struct perf_event *event) { event->pending_disable = 1; - irq_work_queue(&event->pending_irq); + irq_work_queue(&event->pending_disable_irq); } #define MAX_INTERRUPTS (~0ULL) @ kernel/events/core.c:5178 @ static void perf_addr_filters_splice(struct perf_event *event, static void _free_event(struct perf_event *event) { irq_work_sync(&event->pending_irq); + irq_work_sync(&event->pending_disable_irq); unaccount_event(event); @ kernel/events/core.c:6715 @ static void perf_sigtrap(struct perf_event *event) /* * Deliver the pending work in-event-context or follow the context. */ -static void __perf_pending_irq(struct perf_event *event) +static void __perf_pending_disable(struct perf_event *event) { int cpu = READ_ONCE(event->oncpu); @ kernel/events/core.c:6730 @ static void __perf_pending_irq(struct perf_event *event) * Yay, we hit home and are in the context of the event. */ if (cpu == smp_processor_id()) { - if (event->pending_sigtrap) { - event->pending_sigtrap = 0; - perf_sigtrap(event); - local_dec(&event->ctx->nr_pending); - } if (event->pending_disable) { event->pending_disable = 0; perf_event_disable_local(event); @ kernel/events/core.c:6753 @ static void __perf_pending_irq(struct perf_event *event) * irq_work_queue(); // FAILS * * irq_work_run() - * perf_pending_irq() + * perf_pending_disable() * * But the event runs on CPU-B and wants disabling there. */ - irq_work_queue_on(&event->pending_irq, cpu); + irq_work_queue_on(&event->pending_disable_irq, cpu); +} + +static void perf_pending_disable(struct irq_work *entry) +{ + struct perf_event *event = container_of(entry, struct perf_event, pending_disable_irq); + int rctx; + + /* + * If we 'fail' here, that's OK, it means recursion is already disabled + * and we won't recurse 'further'. + */ + rctx = perf_swevent_get_recursion_context(); + __perf_pending_disable(event); + if (rctx >= 0) + perf_swevent_put_recursion_context(rctx); } static void perf_pending_irq(struct irq_work *entry) @ kernel/events/core.c:6795 @ static void perf_pending_irq(struct irq_work *entry) perf_event_wakeup(event); } - __perf_pending_irq(event); - if (rctx >= 0) perf_swevent_put_recursion_context(rctx); } @ kernel/events/core.c:6802 @ static void perf_pending_irq(struct irq_work *entry) static void perf_pending_task(struct callback_head *head) { struct perf_event *event = container_of(head, struct perf_event, pending_task); - int rctx; - - /* - * If we 'fail' here, that's OK, it means recursion is already disabled - * and we won't recurse 'further'. - */ - preempt_disable_notrace(); - rctx = perf_swevent_get_recursion_context(); if (event->pending_work) { event->pending_work = 0; @ kernel/events/core.c:6809 @ static void perf_pending_task(struct callback_head *head) local_dec(&event->ctx->nr_pending); } - if (rctx >= 0) - perf_swevent_put_recursion_context(rctx); - preempt_enable_notrace(); - put_event(event); } @ kernel/events/core.c:9573 @ static int __perf_event_overflow(struct perf_event *event, if (regs) pending_id = hash32_ptr((void *)instruction_pointer(regs)) ?: 1; - if (!event->pending_sigtrap) { - event->pending_sigtrap = pending_id; + if (!event->pending_work) { + event->pending_work = pending_id; local_inc(&event->ctx->nr_pending); + WARN_ON_ONCE(!atomic_long_inc_not_zero(&event->refcount)); + task_work_add(current, &event->pending_task, TWA_RESUME); + /* + * The NMI path returns directly to userland. The + * irq_work is raised as a dummy interrupt to ensure + * regular return path to user is taken and task_work + * is processed. + */ + if (in_nmi()) + irq_work_queue(&event->pending_disable_irq); } else if (event->attr.exclude_kernel && valid_sample) { /* * Should not be able to return to user space without - * consuming pending_sigtrap; with exceptions: + * consuming pending_work; with exceptions: * * 1. Where !exclude_kernel, events can overflow again * in the kernel without returning to user space. @ kernel/events/core.c:9599 @ static int __perf_event_overflow(struct perf_event *event, * To approximate progress (with false negatives), * check 32-bit hash of the current IP. */ - WARN_ON_ONCE(event->pending_sigtrap != pending_id); + WARN_ON_ONCE(event->pending_work != pending_id); } event->pending_addr = 0; if (valid_sample && (data->sample_flags & PERF_SAMPLE_ADDR)) event->pending_addr = data->addr; - irq_work_queue(&event->pending_irq); } READ_ONCE(event->overflow_handler)(event, data, regs); @ kernel/events/core.c:11925 @ perf_event_alloc(struct perf_event_attr *attr, int cpu, init_waitqueue_head(&event->waitq); init_irq_work(&event->pending_irq, perf_pending_irq); + event->pending_disable_irq = IRQ_WORK_INIT_HARD(perf_pending_disable); init_task_work(&event->pending_task, perf_pending_task); mutex_init(&event->mmap_mutex); @ kernel/events/core.c:13040 @ static void sync_child_event(struct perf_event *child_event) &parent_event->child_total_time_running); } +static bool task_work_cb_match(struct callback_head *cb, void *data) +{ + struct perf_event *event = container_of(cb, struct perf_event, pending_task); + + return event == data; +} + static void perf_event_exit_event(struct perf_event *event, struct perf_event_context *ctx) { @ kernel/events/core.c:13086 @ perf_event_exit_event(struct perf_event *event, struct perf_event_context *ctx) * Kick perf_poll() for is_event_hup(); */ perf_event_wakeup(parent_event); + /* + * Cancel pending task_work and update counters if it has not + * yet been delivered to userland. free_event() expects the + * reference counter at 1 and keeping the event around until the + * task return to userland will be a unexpected. + */ + if (event->pending_work && + task_work_cancel_match(current, task_work_cb_match, event)) { + put_event(event); + local_dec(&event->ctx->nr_pending); + } free_event(event); put_event(parent_event); return; @ kernel/ksysfs.c:184 @ KERNEL_ATTR_RO(crash_elfcorehdr_size); #endif /* CONFIG_VMCORE_INFO */ +#if defined(CONFIG_PREEMPT_RT) +static ssize_t realtime_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%d\n", 1); +} +KERNEL_ATTR_RO(realtime); +#endif + /* whether file capabilities are enabled */ static ssize_t fscaps_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) @ kernel/ksysfs.c:290 @ static struct attribute * kernel_attrs[] = { #ifndef CONFIG_TINY_RCU &rcu_expedited_attr.attr, &rcu_normal_attr.attr, +#endif +#ifdef CONFIG_PREEMPT_RT + &realtime_attr.attr, #endif NULL }; @ kernel/locking/lockdep.c:59 @ #include <linux/kprobes.h> #include <linux/lockdep.h> #include <linux/context_tracking.h> +#include <linux/console.h> #include <asm/sections.h> @ kernel/locking/lockdep.c:578 @ static struct lock_trace *save_trace(void) if (!debug_locks_off_graph_unlock()) return NULL; + nbcon_cpu_emergency_enter(); print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!"); dump_stack(); + nbcon_cpu_emergency_exit(); return NULL; } @ kernel/locking/lockdep.c:788 @ static void lockdep_print_held_locks(struct task_struct *p) { int i, depth = READ_ONCE(p->lockdep_depth); + nbcon_cpu_emergency_enter(); + if (!depth) printk("no locks held by %s/%d.\n", p->comm, task_pid_nr(p)); else @ kernel/locking/lockdep.c:800 @ static void lockdep_print_held_locks(struct task_struct *p) * and it's not the current task. */ if (p != current && task_is_running(p)) - return; + goto out; for (i = 0; i < depth; i++) { printk(" #%d: ", i); print_lock(p->held_locks + i); } +out: + nbcon_cpu_emergency_exit(); } static void print_kernel_ident(void) @ kernel/locking/lockdep.c:898 @ look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass) if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) { instrumentation_begin(); debug_locks_off(); + nbcon_cpu_emergency_enter(); printk(KERN_ERR "BUG: looking up invalid subclass: %u\n", subclass); printk(KERN_ERR "turning off the locking correctness validator.\n"); dump_stack(); + nbcon_cpu_emergency_exit(); instrumentation_end(); return NULL; } @ kernel/locking/lockdep.c:981 @ static bool assign_lock_key(struct lockdep_map *lock) else { /* Debug-check: all keys must be persistent! */ debug_locks_off(); + nbcon_cpu_emergency_enter(); pr_err("INFO: trying to register non-static key.\n"); pr_err("The code is fine but needs lockdep annotation, or maybe\n"); pr_err("you didn't initialize this object before use?\n"); pr_err("turning off the locking correctness validator.\n"); dump_stack(); + nbcon_cpu_emergency_exit(); return false; } @ kernel/locking/lockdep.c:1331 @ register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force) return NULL; } + nbcon_cpu_emergency_enter(); print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!"); dump_stack(); + nbcon_cpu_emergency_exit(); return NULL; } nr_lock_classes++; @ kernel/locking/lockdep.c:1366 @ register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force) if (verbose(class)) { graph_unlock(); + nbcon_cpu_emergency_enter(); printk("\nnew class %px: %s", class->key, class->name); if (class->name_version > 1) printk(KERN_CONT "#%d", class->name_version); printk(KERN_CONT "\n"); dump_stack(); + nbcon_cpu_emergency_exit(); if (!graph_lock()) { return NULL; @ kernel/locking/lockdep.c:1411 @ static struct lock_list *alloc_list_entry(void) if (!debug_locks_off_graph_unlock()) return NULL; + nbcon_cpu_emergency_enter(); print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!"); dump_stack(); + nbcon_cpu_emergency_exit(); return NULL; } nr_list_entries++; @ kernel/locking/lockdep.c:2060 @ static noinline void print_circular_bug(struct lock_list *this, depth = get_lock_depth(target); + nbcon_cpu_emergency_enter(); + print_circular_bug_header(target, depth, check_src, check_tgt); parent = get_lock_parent(target); @ kernel/locking/lockdep.c:2080 @ static noinline void print_circular_bug(struct lock_list *this, printk("\nstack backtrace:\n"); dump_stack(); + + nbcon_cpu_emergency_exit(); } static noinline void print_bfs_bug(int ret) @ kernel/locking/lockdep.c:2594 @ print_bad_irq_dependency(struct task_struct *curr, if (!debug_locks_off_graph_unlock() || debug_locks_silent) return; + nbcon_cpu_emergency_enter(); + pr_warn("\n"); pr_warn("=====================================================\n"); pr_warn("WARNING: %s-safe -> %s-unsafe lock order detected\n", @ kernel/locking/lockdep.c:2645 @ print_bad_irq_dependency(struct task_struct *curr, pr_warn(" and %s-irq-unsafe lock:\n", irqclass); next_root->trace = save_trace(); if (!next_root->trace) - return; + goto out; print_shortest_lock_dependencies(forwards_entry, next_root); pr_warn("\nstack backtrace:\n"); dump_stack(); +out: + nbcon_cpu_emergency_exit(); } static const char *state_names[] = { @ kernel/locking/lockdep.c:3016 @ print_deadlock_bug(struct task_struct *curr, struct held_lock *prev, if (!debug_locks_off_graph_unlock() || debug_locks_silent) return; + nbcon_cpu_emergency_enter(); + pr_warn("\n"); pr_warn("============================================\n"); pr_warn("WARNING: possible recursive locking detected\n"); @ kernel/locking/lockdep.c:3040 @ print_deadlock_bug(struct task_struct *curr, struct held_lock *prev, pr_warn("\nstack backtrace:\n"); dump_stack(); + + nbcon_cpu_emergency_exit(); } /* @ kernel/locking/lockdep.c:3639 @ static void print_collision(struct task_struct *curr, struct held_lock *hlock_next, struct lock_chain *chain) { + nbcon_cpu_emergency_enter(); + pr_warn("\n"); pr_warn("============================\n"); pr_warn("WARNING: chain_key collision\n"); @ kernel/locking/lockdep.c:3657 @ static void print_collision(struct task_struct *curr, pr_warn("\nstack backtrace:\n"); dump_stack(); + + nbcon_cpu_emergency_exit(); } #endif @ kernel/locking/lockdep.c:3749 @ static inline int add_chain_cache(struct task_struct *curr, if (!debug_locks_off_graph_unlock()) return 0; + nbcon_cpu_emergency_enter(); print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!"); dump_stack(); + nbcon_cpu_emergency_exit(); return 0; } chain->chain_key = chain_key; @ kernel/locking/lockdep.c:3769 @ static inline int add_chain_cache(struct task_struct *curr, if (!debug_locks_off_graph_unlock()) return 0; + nbcon_cpu_emergency_enter(); print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!"); dump_stack(); + nbcon_cpu_emergency_exit(); return 0; } @ kernel/locking/lockdep.c:4011 @ print_usage_bug(struct task_struct *curr, struct held_lock *this, if (!debug_locks_off() || debug_locks_silent) return; + nbcon_cpu_emergency_enter(); + pr_warn("\n"); pr_warn("================================\n"); pr_warn("WARNING: inconsistent lock state\n"); @ kernel/locking/lockdep.c:4041 @ print_usage_bug(struct task_struct *curr, struct held_lock *this, pr_warn("\nstack backtrace:\n"); dump_stack(); + + nbcon_cpu_emergency_exit(); } /* @ kernel/locking/lockdep.c:4077 @ print_irq_inversion_bug(struct task_struct *curr, if (!debug_locks_off_graph_unlock() || debug_locks_silent) return; + nbcon_cpu_emergency_enter(); + pr_warn("\n"); pr_warn("========================================================\n"); pr_warn("WARNING: possible irq lock inversion dependency detected\n"); @ kernel/locking/lockdep.c:4119 @ print_irq_inversion_bug(struct task_struct *curr, pr_warn("\nthe shortest dependencies between 2nd lock and 1st lock:\n"); root->trace = save_trace(); if (!root->trace) - return; + goto out; print_shortest_lock_dependencies(other, root); pr_warn("\nstack backtrace:\n"); dump_stack(); +out: + nbcon_cpu_emergency_exit(); } /* @ kernel/locking/lockdep.c:4202 @ void print_irqtrace_events(struct task_struct *curr) { const struct irqtrace_events *trace = &curr->irqtrace; + nbcon_cpu_emergency_enter(); + printk("irq event stamp: %u\n", trace->irq_events); printk("hardirqs last enabled at (%u): [<%px>] %pS\n", trace->hardirq_enable_event, (void *)trace->hardirq_enable_ip, @ kernel/locking/lockdep.c:4217 @ void print_irqtrace_events(struct task_struct *curr) printk("softirqs last disabled at (%u): [<%px>] %pS\n", trace->softirq_disable_event, (void *)trace->softirq_disable_ip, (void *)trace->softirq_disable_ip); + + nbcon_cpu_emergency_exit(); } static int HARDIRQ_verbose(struct lock_class *class) @ kernel/locking/lockdep.c:4739 @ static int mark_lock(struct task_struct *curr, struct held_lock *this, * We must printk outside of the graph_lock: */ if (ret == 2) { + nbcon_cpu_emergency_enter(); printk("\nmarked lock as {%s}:\n", usage_str[new_bit]); print_lock(this); print_irqtrace_events(curr); dump_stack(); + nbcon_cpu_emergency_exit(); } return ret; @ kernel/locking/lockdep.c:4785 @ print_lock_invalid_wait_context(struct task_struct *curr, if (debug_locks_silent) return 0; + nbcon_cpu_emergency_enter(); + pr_warn("\n"); pr_warn("=============================\n"); pr_warn("[ BUG: Invalid wait context ]\n"); @ kernel/locking/lockdep.c:4806 @ print_lock_invalid_wait_context(struct task_struct *curr, pr_warn("stack backtrace:\n"); dump_stack(); + nbcon_cpu_emergency_exit(); + return 0; } @ kernel/locking/lockdep.c:5012 @ print_lock_nested_lock_not_held(struct task_struct *curr, if (debug_locks_silent) return; + nbcon_cpu_emergency_enter(); + pr_warn("\n"); pr_warn("==================================\n"); pr_warn("WARNING: Nested lock was not taken\n"); @ kernel/locking/lockdep.c:5034 @ print_lock_nested_lock_not_held(struct task_struct *curr, pr_warn("\nstack backtrace:\n"); dump_stack(); + + nbcon_cpu_emergency_exit(); } static int __lock_is_held(const struct lockdep_map *lock, int read); @ kernel/locking/lockdep.c:5081 @ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass, debug_class_ops_inc(class); if (very_verbose(class)) { + nbcon_cpu_emergency_enter(); printk("\nacquire class [%px] %s", class->key, class->name); if (class->name_version > 1) printk(KERN_CONT "#%d", class->name_version); printk(KERN_CONT "\n"); dump_stack(); + nbcon_cpu_emergency_exit(); } /* @ kernel/locking/lockdep.c:5214 @ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass, #endif if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) { debug_locks_off(); + nbcon_cpu_emergency_enter(); print_lockdep_off("BUG: MAX_LOCK_DEPTH too low!"); printk(KERN_DEBUG "depth: %i max: %lu!\n", curr->lockdep_depth, MAX_LOCK_DEPTH); @ kernel/locking/lockdep.c:5222 @ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass, lockdep_print_held_locks(current); debug_show_all_locks(); dump_stack(); + nbcon_cpu_emergency_exit(); return 0; } @ kernel/locking/lockdep.c:5242 @ static void print_unlock_imbalance_bug(struct task_struct *curr, if (debug_locks_silent) return; + nbcon_cpu_emergency_enter(); + pr_warn("\n"); pr_warn("=====================================\n"); pr_warn("WARNING: bad unlock balance detected!\n"); @ kernel/locking/lockdep.c:5260 @ static void print_unlock_imbalance_bug(struct task_struct *curr, pr_warn("\nstack backtrace:\n"); dump_stack(); + + nbcon_cpu_emergency_exit(); } static noinstr int match_held_lock(const struct held_lock *hlock, @ kernel/locking/lockdep.c:5965 @ static void print_lock_contention_bug(struct task_struct *curr, if (debug_locks_silent) return; + nbcon_cpu_emergency_enter(); + pr_warn("\n"); pr_warn("=================================\n"); pr_warn("WARNING: bad contention detected!\n"); @ kernel/locking/lockdep.c:5983 @ static void print_lock_contention_bug(struct task_struct *curr, pr_warn("\nstack backtrace:\n"); dump_stack(); + + nbcon_cpu_emergency_exit(); } static void @ kernel/locking/lockdep.c:6598 @ print_freed_lock_bug(struct task_struct *curr, const void *mem_from, if (debug_locks_silent) return; + nbcon_cpu_emergency_enter(); + pr_warn("\n"); pr_warn("=========================\n"); pr_warn("WARNING: held lock freed!\n"); @ kernel/locking/lockdep.c:6612 @ print_freed_lock_bug(struct task_struct *curr, const void *mem_from, pr_warn("\nstack backtrace:\n"); dump_stack(); + + nbcon_cpu_emergency_exit(); } static inline int not_in_range(const void* mem_from, unsigned long mem_len, @ kernel/locking/lockdep.c:6660 @ static void print_held_locks_bug(void) if (debug_locks_silent) return; + nbcon_cpu_emergency_enter(); + pr_warn("\n"); pr_warn("====================================\n"); pr_warn("WARNING: %s/%d still has locks held!\n", @ kernel/locking/lockdep.c:6671 @ static void print_held_locks_bug(void) lockdep_print_held_locks(current); pr_warn("\nstack backtrace:\n"); dump_stack(); + + nbcon_cpu_emergency_exit(); } void debug_check_no_locks_held(void) @ kernel/locking/lockdep.c:6691 @ void debug_show_all_locks(void) pr_warn("INFO: lockdep is turned off.\n"); return; } + nbcon_cpu_emergency_enter(); pr_warn("\nShowing all locks held in the system:\n"); rcu_read_lock(); @ kernel/locking/lockdep.c:6706 @ void debug_show_all_locks(void) pr_warn("\n"); pr_warn("=============================================\n\n"); + nbcon_cpu_emergency_exit(); } EXPORT_SYMBOL_GPL(debug_show_all_locks); #endif @ kernel/locking/lockdep.c:6732 @ asmlinkage __visible void lockdep_sys_exit(void) if (unlikely(curr->lockdep_depth)) { if (!debug_locks_off()) return; + nbcon_cpu_emergency_enter(); pr_warn("\n"); pr_warn("================================================\n"); pr_warn("WARNING: lock held when returning to user space!\n"); @ kernel/locking/lockdep.c:6741 @ asmlinkage __visible void lockdep_sys_exit(void) pr_warn("%s/%d is leaving the kernel with locks still held!\n", curr->comm, curr->pid); lockdep_print_held_locks(curr); + nbcon_cpu_emergency_exit(); } /* @ kernel/locking/lockdep.c:6758 @ void lockdep_rcu_suspicious(const char *file, const int line, const char *s) bool rcu = warn_rcu_enter(); /* Note: the following can be executed concurrently, so be careful. */ + nbcon_cpu_emergency_enter(); pr_warn("\n"); pr_warn("=============================\n"); pr_warn("WARNING: suspicious RCU usage\n"); @ kernel/locking/lockdep.c:6797 @ void lockdep_rcu_suspicious(const char *file, const int line, const char *s) lockdep_print_held_locks(curr); pr_warn("\nstack backtrace:\n"); dump_stack(); + nbcon_cpu_emergency_exit(); warn_rcu_exit(rcu); } EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious); @ kernel/panic.c:371 @ void panic(const char *fmt, ...) panic_other_cpus_shutdown(_crash_kexec_post_notifiers); + printk_legacy_allow_panic_sync(); + /* * Run any panic handlers, including those that might need to * add information to the kmsg dump output. @ kernel/panic.c:462 @ void panic(const char *fmt, ...) * Explicitly flush the kernel log buffer one last time. */ console_flush_on_panic(CONSOLE_FLUSH_PENDING); + nbcon_atomic_flush_unsafe(); local_irq_enable(); for (i = 0; ; i += PANIC_TIMER_STEP) { @ kernel/panic.c:641 @ bool oops_may_print(void) */ void oops_enter(void) { + nbcon_cpu_emergency_enter(); tracing_off(); /* can't trust the integrity of the kernel anymore: */ debug_locks_off(); @ kernel/panic.c:664 @ void oops_exit(void) { do_oops_enter_exit(); print_oops_end_marker(); + nbcon_cpu_emergency_exit(); kmsg_dump(KMSG_DUMP_OOPS); } @ kernel/panic.c:676 @ struct warn_args { void __warn(const char *file, int line, void *caller, unsigned taint, struct pt_regs *regs, struct warn_args *args) { + nbcon_cpu_emergency_enter(); + disable_trace_on_warning(); if (file) @ kernel/panic.c:713 @ void __warn(const char *file, int line, void *caller, unsigned taint, /* Just a warning, don't kill lockdep. */ add_taint(taint, LOCKDEP_STILL_OK); + + nbcon_cpu_emergency_exit(); } #ifdef CONFIG_BUG @ kernel/printk/internal.h:5 @ /* * internal.h - printk internal definitions */ -#include <linux/percpu.h> #include <linux/console.h> -#include "printk_ringbuffer.h" +#include <linux/jump_label.h> +#include <linux/percpu.h> +#include <linux/types.h> #if defined(CONFIG_PRINTK) && defined(CONFIG_SYSCTL) +struct ctl_table; void __init printk_sysctl_init(void); int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write, void *buffer, size_t *lenp, loff_t *ppos); @ kernel/printk/internal.h:25 @ int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write, (con->flags & CON_BOOT) ? "boot" : "", \ con->name, con->index, ##__VA_ARGS__) +#ifdef CONFIG_PREEMPT_RT +# define force_printkthreads() (true) +#else +DECLARE_STATIC_KEY_FALSE(force_printkthreads_key); +# define force_printkthreads() (static_branch_unlikely(&force_printkthreads_key)) +#endif + #ifdef CONFIG_PRINTK #ifdef CONFIG_PRINTK_CALLER @ kernel/printk/internal.h:55 @ enum printk_info_flags { LOG_CONT = 8, /* text is a fragment of a continuation line */ }; +struct printk_ringbuffer; +struct dev_printk_info; + extern struct printk_ringbuffer *prb; +extern bool printk_threads_enabled; __printf(4, 0) int vprintk_store(int facility, int level, @ kernel/printk/internal.h:69 @ int vprintk_store(int facility, int level, __printf(1, 0) int vprintk_default(const char *fmt, va_list args); __printf(1, 0) int vprintk_deferred(const char *fmt, va_list args); +void __printk_safe_enter(void); +void __printk_safe_exit(void); + bool printk_percpu_data_ready(void); #define printk_safe_enter_irqsave(flags) \ @ kernel/printk/internal.h:90 @ void defer_console_output(void); u16 printk_parse_prefix(const char *text, int *level, enum printk_info_flags *flags); +void console_lock_spinning_enable(void); +int console_lock_spinning_disable_and_check(int cookie); u64 nbcon_seq_read(struct console *con); void nbcon_seq_force(struct console *con, u64 seq); bool nbcon_alloc(struct console *con); void nbcon_init(struct console *con); void nbcon_free(struct console *con); +enum nbcon_prio nbcon_get_default_prio(void); +void nbcon_atomic_flush_pending(void); +bool nbcon_legacy_emit_next_record(struct console *con, bool *handover, + int cookie, bool use_atomic); +void nbcon_kthread_create(struct console *con); +void nbcon_wake_threads(void); +void nbcon_legacy_kthread_create(void); + +/* + * Check if the given console is currently capable and allowed to print + * records. Note that this function does not consider the current context, + * which can also play a role in deciding if @con can be used to print + * records. + */ +static inline bool console_is_usable(struct console *con, short flags, bool use_atomic) +{ + if (!(flags & CON_ENABLED)) + return false; + + if ((flags & CON_SUSPENDED)) + return false; + + if (flags & CON_NBCON) { + if (use_atomic) { + if (!con->write_atomic) + return false; + } else { + if (!con->write_thread) + return false; + } + } else { + if (!con->write) + return false; + } + + /* + * Console drivers may assume that per-cpu resources have been + * allocated. So unless they're explicitly marked as being able to + * cope (CON_ANYTIME) don't call them until this CPU is officially up. + */ + if (!cpu_online(raw_smp_processor_id()) && !(flags & CON_ANYTIME)) + return false; + + return true; +} + +/** + * nbcon_kthread_wake - Wake up a printk thread + * @con: Console to operate on + */ +static inline void nbcon_kthread_wake(struct console *con) +{ + /* + * Guarantee any new records can be seen by tasks preparing to wait + * before this context checks if the rcuwait is empty. + * + * The full memory barrier in rcuwait_wake_up() pairs with the full + * memory barrier within set_current_state() of + * ___rcuwait_wait_event(), which is called after prepare_to_rcuwait() + * adds the waiter but before it has checked the wait condition. + * + * This pairs with nbcon_kthread_func:A. + */ + rcuwait_wake_up(&con->rcuwait); /* LMM(nbcon_kthread_wake:A) */ +} #else @ kernel/printk/internal.h:170 @ void nbcon_free(struct console *con); #define PRINTK_MESSAGE_MAX 0 #define PRINTKRB_RECORD_MAX 0 +static inline void nbcon_kthread_wake(struct console *con) { } +static inline void nbcon_kthread_create(struct console *con) { } +#define printk_threads_enabled (false) + /* * In !PRINTK builds we still export console_sem * semaphore and some of console functions (console_unlock()/etc.), so @ kernel/printk/internal.h:188 @ static inline void nbcon_seq_force(struct console *con, u64 seq) { } static inline bool nbcon_alloc(struct console *con) { return false; } static inline void nbcon_init(struct console *con) { } static inline void nbcon_free(struct console *con) { } +static inline enum nbcon_prio nbcon_get_default_prio(void) { return NBCON_PRIO_NONE; } +static inline void nbcon_atomic_flush_pending(void) { } +static inline bool nbcon_legacy_emit_next_record(struct console *con, bool *handover, + int cookie, bool use_atomic) { return false; } + +static inline bool console_is_usable(struct console *con, short flags, + bool use_atomic) { return false; } #endif /* CONFIG_PRINTK */ +extern bool have_boot_console; +extern bool have_legacy_console; + +/* + * Specifies if the console lock/unlock dance is needed for console + * printing. If @have_boot_console is true, the nbcon consoles will + * be printed serially along with the legacy consoles because nbcon + * consoles cannot print simultaneously with boot consoles. + */ +#define printing_via_unlock (have_legacy_console || have_boot_console) + extern struct printk_buffers printk_shared_pbufs; /** @ kernel/printk/internal.h:243 @ bool printk_get_next_message(struct printk_message *pmsg, u64 seq, #ifdef CONFIG_PRINTK void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped); +void console_prepend_replay(struct printk_message *pmsg); #endif @ kernel/printk/nbcon.c:5 @ // Copyright (C) 2022 Linutronix GmbH, John Ogness // Copyright (C) 2022 Intel, Thomas Gleixner -#include <linux/kernel.h> +#include <linux/atomic.h> +#include <linux/bug.h> #include <linux/console.h> #include <linux/delay.h> +#include <linux/errno.h> +#include <linux/export.h> +#include <linux/init.h> +#include <linux/irqflags.h> +#include <linux/kthread.h> +#include <linux/minmax.h> +#include <linux/percpu.h> +#include <linux/preempt.h> #include <linux/slab.h> +#include <linux/smp.h> +#include <linux/stddef.h> +#include <linux/string.h> +#include <linux/syscore_ops.h> +#include <linux/types.h> #include "internal.h" +#include "printk_ringbuffer.h" /* * Printk console printing implementation for consoles which does not depend * on the legacy style console_lock mechanism. @ kernel/printk/nbcon.c:190 @ void nbcon_seq_force(struct console *con, u64 seq) u64 valid_seq = max_t(u64, seq, prb_first_valid_seq(prb)); atomic_long_set(&ACCESS_PRIVATE(con, nbcon_seq), __u64seq_to_ulseq(valid_seq)); - - /* Clear con->seq since nbcon consoles use con->nbcon_seq instead. */ - con->seq = 0; } /** @ kernel/printk/nbcon.c:216 @ static void nbcon_seq_try_update(struct nbcon_context *ctxt, u64 new_seq) } } +bool printk_threads_enabled __ro_after_init; + /** * nbcon_context_try_acquire_direct - Try to acquire directly * @ctxt: The context of the caller @ kernel/printk/nbcon.c:548 @ static struct printk_buffers panic_nbcon_pbufs; * nbcon_context_try_acquire - Try to acquire nbcon console * @ctxt: The context of the caller * + * Context: Any context which could not be migrated to another CPU. * Return: True if the console was acquired. False otherwise. * * If the caller allowed an unsafe hostile takeover, on success the @ kernel/printk/nbcon.c:556 @ static struct printk_buffers panic_nbcon_pbufs; * in an unsafe state. Otherwise, on success the caller may assume * the console is not in an unsafe state. */ -__maybe_unused static bool nbcon_context_try_acquire(struct nbcon_context *ctxt) { unsigned int cpu = smp_processor_id(); @ kernel/printk/nbcon.c:841 @ bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt) } EXPORT_SYMBOL_GPL(nbcon_exit_unsafe); +/** + * nbcon_reacquire - Reacquire a console after losing ownership + * @wctxt: The write context that was handed to the write function + * + * Since ownership can be lost at any time due to handover or takeover, a + * printing context _should_ be prepared to back out immediately and + * carefully. However, there are many scenarios where the context _must_ + * reacquire ownership in order to finalize or revert hardware changes. + * + * This function allows a context to reacquire ownership using the same + * priority as its previous ownership. + * + * Note that for printing contexts, after a successful reacquire the + * context will have no output buffer because that has been lost. This + * function cannot be used to resume printing. + */ +void nbcon_reacquire(struct nbcon_write_context *wctxt) +{ + struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt); + struct console *con = ctxt->console; + struct nbcon_state cur; + + while (!nbcon_context_try_acquire(ctxt)) + cpu_relax(); + + wctxt->outbuf = NULL; + wctxt->len = 0; + nbcon_state_read(con, &cur); + wctxt->unsafe_takeover = cur.unsafe_takeover; +} +EXPORT_SYMBOL_GPL(nbcon_reacquire); + /** * nbcon_emit_next_record - Emit a record in the acquired context * @wctxt: The write context that will be handed to the write function + * @use_atomic: True if the write_atomic callback is to be used * * Return: True if this context still owns the console. False if * ownership was handed over or taken. @ kernel/printk/nbcon.c:890 @ EXPORT_SYMBOL_GPL(nbcon_exit_unsafe); * When true is returned, @wctxt->ctxt.backlog indicates whether there are * still records pending in the ringbuffer, */ -__maybe_unused -static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt) +static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt, bool use_atomic) { struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt); struct console *con = ctxt->console; @ kernel/printk/nbcon.c:901 @ static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt) unsigned long con_dropped; struct nbcon_state cur; unsigned long dropped; - bool done; + unsigned long ulseq; /* * The printk buffers are filled within an unsafe section. This @ kernel/printk/nbcon.c:927 @ static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt) if (dropped && !is_extended) console_prepend_dropped(&pmsg, dropped); + /* + * If the previous owner was assigned the same record, this context + * has taken over ownership and is replaying the record. Prepend a + * message to let the user know the record is replayed. + */ + ulseq = atomic_long_read(&ACCESS_PRIVATE(con, nbcon_prev_seq)); + if (__ulseq_to_u64seq(prb, ulseq) == pmsg.seq) { + console_prepend_replay(&pmsg); + } else { + /* + * Ensure this context is still the owner before trying to + * update @nbcon_prev_seq. Otherwise the value in @ulseq may + * not be from the previous owner. + */ + nbcon_state_read(con, &cur); + if (!nbcon_context_can_proceed(ctxt, &cur)) + return false; + + atomic_long_try_cmpxchg(&ACCESS_PRIVATE(con, nbcon_prev_seq), &ulseq, + __u64seq_to_ulseq(pmsg.seq)); + } + if (!nbcon_context_exit_unsafe(ctxt)) return false; @ kernel/printk/nbcon.c:962 @ static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt) nbcon_state_read(con, &cur); wctxt->unsafe_takeover = cur.unsafe_takeover; - if (con->write_atomic) { - done = con->write_atomic(con, wctxt); + if (use_atomic && + con->write_atomic) { + con->write_atomic(con, wctxt); + + } else if (!use_atomic && + con->write_thread) { + con->write_thread(con, wctxt); + } else { - nbcon_context_release(ctxt); + /* + * This function should never be called for legacy consoles. + * Handle it as if ownership was lost and try to continue. + */ WARN_ON_ONCE(1); - done = false; + nbcon_context_release(ctxt); + return false; } - /* If not done, the emit was aborted. */ - if (!done) + if (!wctxt->outbuf) { + /* + * Ownership was lost and reacquired by the driver. + * Handle it as if ownership was lost and try to continue. + */ + nbcon_context_release(ctxt); return false; + } /* * Since any dropped message was successfully output, reset the @ kernel/printk/nbcon.c:1014 @ static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt) return nbcon_context_exit_unsafe(ctxt); } +/** + * nbcon_kthread_should_wakeup - Check whether a printer thread should wakeup + * @con: Console to operate on + * @ctxt: The acquire context that contains the state + * at console_acquire() + * + * Return: True if the thread should shutdown or if the console is + * allowed to print and a record is available. False otherwise. + * + * After the thread wakes up, it must first check if it should shutdown before + * attempting any printing. + */ +static bool nbcon_kthread_should_wakeup(struct console *con, struct nbcon_context *ctxt) +{ + bool ret = false; + short flags; + int cookie; + + if (kthread_should_stop()) + return true; + + cookie = console_srcu_read_lock(); + + flags = console_srcu_read_flags(con); + if (console_is_usable(con, flags, false)) { + /* Bring the sequence in @ctxt up to date */ + ctxt->seq = nbcon_seq_read(con); + + ret = prb_read_valid(prb, ctxt->seq, NULL); + } + + console_srcu_read_unlock(cookie); + return ret; +} + +/** + * nbcon_kthread_func - The printer thread function + * @__console: Console to operate on + */ +static int nbcon_kthread_func(void *__console) +{ + struct console *con = __console; + struct nbcon_write_context wctxt = { + .ctxt.console = con, + .ctxt.prio = NBCON_PRIO_NORMAL, + }; + struct nbcon_context *ctxt = &ACCESS_PRIVATE(&wctxt, ctxt); + unsigned long flags; + short con_flags; + bool backlog; + int cookie; + int ret; + +wait_for_event: + /* + * Guarantee this task is visible on the rcuwait before + * checking the wake condition. + * + * The full memory barrier within set_current_state() of + * ___rcuwait_wait_event() pairs with the full memory + * barrier within rcuwait_has_sleeper(). + * + * This pairs with rcuwait_has_sleeper:A and nbcon_kthread_wake:A. + */ + ret = rcuwait_wait_event(&con->rcuwait, + nbcon_kthread_should_wakeup(con, ctxt), + TASK_INTERRUPTIBLE); /* LMM(nbcon_kthread_func:A) */ + + if (kthread_should_stop()) + return 0; + + /* Wait was interrupted by a spurious signal, go back to sleep. */ + if (ret) + goto wait_for_event; + + do { + backlog = false; + + cookie = console_srcu_read_lock(); + + con_flags = console_srcu_read_flags(con); + + if (console_is_usable(con, con_flags, false)) { + con->device_lock(con, &flags); + + /* + * Ensure this stays on the CPU to make handover and + * takeover possible. + */ + cant_migrate(); + + if (nbcon_context_try_acquire(ctxt)) { + /* + * If the emit fails, this context is no + * longer the owner. + */ + if (nbcon_emit_next_record(&wctxt, false)) { + nbcon_context_release(ctxt); + backlog = ctxt->backlog; + } + } + + con->device_unlock(con, flags); + } + + console_srcu_read_unlock(cookie); + + } while (backlog); + + goto wait_for_event; +} + +/** + * nbcon_irq_work - irq work to wake printk thread + * @irq_work: The irq work to operate on + */ +static void nbcon_irq_work(struct irq_work *irq_work) +{ + struct console *con = container_of(irq_work, struct console, irq_work); + + nbcon_kthread_wake(con); +} + +static inline bool rcuwait_has_sleeper(struct rcuwait *w) +{ + bool has_sleeper; + + rcu_read_lock(); + /* + * Guarantee any new records can be seen by tasks preparing to wait + * before this context checks if the rcuwait is empty. + * + * This full memory barrier pairs with the full memory barrier within + * set_current_state() of ___rcuwait_wait_event(), which is called + * after prepare_to_rcuwait() adds the waiter but before it has + * checked the wait condition. + * + * This pairs with nbcon_kthread_func:A. + */ + smp_mb(); /* LMM(rcuwait_has_sleeper:A) */ + has_sleeper = !!rcu_dereference(w->task); + rcu_read_unlock(); + + return has_sleeper; +} + +/** + * nbcon_wake_threads - Wake up printing threads using irq_work + */ +void nbcon_wake_threads(void) +{ + struct console *con; + int cookie; + + cookie = console_srcu_read_lock(); + for_each_console_srcu(con) { + /* + * Only schedule irq_work if the printing thread is + * actively waiting. If not waiting, the thread will + * notice by itself that it has work to do. + */ + if (con->kthread && rcuwait_has_sleeper(&con->rcuwait)) + irq_work_queue(&con->irq_work); + } + console_srcu_read_unlock(cookie); +} + +/* Track the nbcon emergency nesting per CPU. */ +static DEFINE_PER_CPU(unsigned int, nbcon_pcpu_emergency_nesting); +static unsigned int early_nbcon_pcpu_emergency_nesting __initdata; + +/** + * nbcon_get_cpu_emergency_nesting - Get the per CPU emergency nesting pointer + * + * Return: Either a pointer to the per CPU emergency nesting counter of + * the current CPU or to the init data during early boot. + */ +static __ref unsigned int *nbcon_get_cpu_emergency_nesting(void) +{ + /* + * The value of __printk_percpu_data_ready gets set in normal + * context and before SMP initialization. As a result it could + * never change while inside an nbcon emergency section. + */ + if (!printk_percpu_data_ready()) + return &early_nbcon_pcpu_emergency_nesting; + + return this_cpu_ptr(&nbcon_pcpu_emergency_nesting); +} + +/** + * nbcon_emit_one - Print one record for an nbcon console using the + * specified callback + * @wctxt: An initialized write context struct to use for this context + * @use_atomic: True if the write_atomic callback is to be used + * + * Return: False if it is known there are no more records to print, + * otherwise true. + * + * This is an internal helper to handle the locking of the console before + * calling nbcon_emit_next_record(). + */ +static bool nbcon_emit_one(struct nbcon_write_context *wctxt, bool use_atomic) +{ + struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt); + + if (!nbcon_context_try_acquire(ctxt)) + return true; + + /* + * nbcon_emit_next_record() returns false when the console was + * handed over or taken over. In both cases the context is no + * longer valid. + */ + if (!nbcon_emit_next_record(wctxt, use_atomic)) + return true; + + nbcon_context_release(ctxt); + + return ctxt->backlog; +} + +/** + * nbcon_get_default_prio - The appropriate nbcon priority to use for nbcon + * printing on the current CPU + * + * Context: Any context which could not be migrated to another CPU. + * Return: The nbcon_prio to use for acquiring an nbcon console in this + * context for printing. + */ +enum nbcon_prio nbcon_get_default_prio(void) +{ + unsigned int *cpu_emergency_nesting; + + if (this_cpu_in_panic()) + return NBCON_PRIO_PANIC; + + cpu_emergency_nesting = nbcon_get_cpu_emergency_nesting(); + if (*cpu_emergency_nesting) + return NBCON_PRIO_EMERGENCY; + + return NBCON_PRIO_NORMAL; +} + +/** + * nbcon_legacy_emit_next_record - Print one record for an nbcon console + * in legacy contexts + * @con: The console to print on + * @handover: Will be set to true if a printk waiter has taken over the + * console_lock, in which case the caller is no longer holding + * both the console_lock and the SRCU read lock. Otherwise it + * is set to false. + * @cookie: The cookie from the SRCU read lock. + * @use_atomic: True if the write_atomic callback is to be used + * + * Context: Any context except NMI. + * Return: False if the given console has no next record to print, + * otherwise true. + * + * This function is meant to be called by console_flush_all() to print records + * on nbcon consoles from legacy context (printing via console unlocking). + * Essentially it is the nbcon version of console_emit_next_record(). + */ +bool nbcon_legacy_emit_next_record(struct console *con, bool *handover, + int cookie, bool use_atomic) +{ + struct nbcon_write_context wctxt = { }; + struct nbcon_context *ctxt = &ACCESS_PRIVATE(&wctxt, ctxt); + unsigned long flags; + bool progress; + + *handover = false; + + ctxt->console = con; + + if (use_atomic) { + /* Use the same procedure as console_emit_next_record(). */ + printk_safe_enter_irqsave(flags); + console_lock_spinning_enable(); + stop_critical_timings(); + + ctxt->prio = nbcon_get_default_prio(); + progress = nbcon_emit_one(&wctxt, use_atomic); + + start_critical_timings(); + *handover = console_lock_spinning_disable_and_check(cookie); + printk_safe_exit_irqrestore(flags); + } else { + con->device_lock(con, &flags); + cant_migrate(); + + ctxt->prio = nbcon_get_default_prio(); + progress = nbcon_emit_one(&wctxt, use_atomic); + + con->device_unlock(con, flags); + } + + return progress; +} + +/** + * __nbcon_atomic_flush_pending_con - Flush specified nbcon console using its + * write_atomic() callback + * @con: The nbcon console to flush + * @stop_seq: Flush up until this record + * @allow_unsafe_takeover: True, to allow unsafe hostile takeovers + * + * Return: True if taken over while printing. Otherwise false. + * + * If flushing up to @stop_seq was not successful, it only makes sense for the + * caller to try again when true was returned. When false is returned, either + * there are no more records available to read or this context is not allowed + * to acquire the console. + */ +static bool __nbcon_atomic_flush_pending_con(struct console *con, u64 stop_seq, + bool allow_unsafe_takeover) +{ + struct nbcon_write_context wctxt = { }; + struct nbcon_context *ctxt = &ACCESS_PRIVATE(&wctxt, ctxt); + + ctxt->console = con; + ctxt->spinwait_max_us = 2000; + ctxt->prio = nbcon_get_default_prio(); + ctxt->allow_unsafe_takeover = allow_unsafe_takeover; + + if (!nbcon_context_try_acquire(ctxt)) + return false; + + while (nbcon_seq_read(con) < stop_seq) { + /* + * nbcon_emit_next_record() returns false when the console was + * handed over or taken over. In both cases the context is no + * longer valid. + */ + if (!nbcon_emit_next_record(&wctxt, true)) + return true; + + if (!ctxt->backlog) + break; + } + + nbcon_context_release(ctxt); + + return false; +} + +/** + * __nbcon_atomic_flush_pending - Flush all nbcon consoles using their + * write_atomic() callback + * @stop_seq: Flush up until this record + * @allow_unsafe_takeover: True, to allow unsafe hostile takeovers + */ +static void __nbcon_atomic_flush_pending(u64 stop_seq, bool allow_unsafe_takeover) +{ + struct console *con; + bool should_retry; + int cookie; + + do { + should_retry = false; + + cookie = console_srcu_read_lock(); + for_each_console_srcu(con) { + short flags = console_srcu_read_flags(con); + unsigned long irq_flags; + + if (!(flags & CON_NBCON)) + continue; + + if (!console_is_usable(con, flags, true)) + continue; + + if (nbcon_seq_read(con) >= stop_seq) + continue; + + /* + * Atomic flushing does not use console driver + * synchronization (i.e. it does not hold the port + * lock for uart consoles). Therefore IRQs must be + * disabled to avoid being interrupted and then + * calling into a driver that will deadlock trying + * to acquire console ownership. + */ + local_irq_save(irq_flags); + + should_retry |= __nbcon_atomic_flush_pending_con(con, stop_seq, + allow_unsafe_takeover); + local_irq_restore(irq_flags); + } + console_srcu_read_unlock(cookie); + } while (should_retry); +} + +/** + * nbcon_atomic_flush_pending - Flush all nbcon consoles using their + * write_atomic() callback + * + * Flush the backlog up through the currently newest record. Any new + * records added while flushing will not be flushed. This is to avoid + * one CPU printing unbounded because other CPUs continue to add records. + */ +void nbcon_atomic_flush_pending(void) +{ + __nbcon_atomic_flush_pending(prb_next_reserve_seq(prb), false); +} + +/** + * nbcon_atomic_flush_unsafe - Flush all nbcon consoles using their + * write_atomic() callback and allowing unsafe hostile takeovers + * + * Flush the backlog up through the currently newest record. Unsafe hostile + * takeovers will be performed, if necessary. + */ +void nbcon_atomic_flush_unsafe(void) +{ + __nbcon_atomic_flush_pending(prb_next_reserve_seq(prb), true); +} + +/** + * nbcon_cpu_emergency_enter - Enter an emergency section where printk() + * messages for that CPU are only stored + * + * Upon exiting the emergency section, all stored messages are flushed. + * + * Context: Any context. Disables preemption. + * + * When within an emergency section, no printing occurs on that CPU. This + * is to allow all emergency messages to be dumped into the ringbuffer before + * flushing the ringbuffer. The actual printing occurs when exiting the + * outermost emergency section. + */ +void nbcon_cpu_emergency_enter(void) +{ + unsigned int *cpu_emergency_nesting; + + preempt_disable(); + + cpu_emergency_nesting = nbcon_get_cpu_emergency_nesting(); + (*cpu_emergency_nesting)++; +} + +/** + * nbcon_cpu_emergency_exit - Exit an emergency section and flush the + * stored messages + * + * Flushing only occurs when exiting all nesting for the CPU. + * + * Context: Any context. Enables preemption. + */ +void nbcon_cpu_emergency_exit(void) +{ + unsigned int *cpu_emergency_nesting; + bool do_trigger_flush = false; + + cpu_emergency_nesting = nbcon_get_cpu_emergency_nesting(); + + WARN_ON_ONCE(*cpu_emergency_nesting == 0); + + if (*cpu_emergency_nesting == 1) { + nbcon_atomic_flush_pending(); + do_trigger_flush = true; + } + + /* Undo the nesting count of nbcon_cpu_emergency_enter(). */ + (*cpu_emergency_nesting)--; + + preempt_enable(); + + if (do_trigger_flush) + printk_trigger_flush(); +} + +/** + * nbcon_kthread_stop - Stop a printer thread + * @con: Console to operate on + */ +static void nbcon_kthread_stop(struct console *con) +{ + lockdep_assert_console_list_lock_held(); + + if (!con->kthread) + return; + + kthread_stop(con->kthread); + con->kthread = NULL; +} + +/** + * nbcon_kthread_create - Create a printer thread + * @con: Console to operate on + * + * If it fails, let the console proceed. The atomic part might + * be usable and useful. + */ +void nbcon_kthread_create(struct console *con) +{ + struct task_struct *kt; + + lockdep_assert_console_list_lock_held(); + + if (!(con->flags & CON_NBCON) || !con->write_thread) + return; + + if (!printk_threads_enabled || con->kthread) + return; + + /* + * Printer threads cannot be started as long as any boot console is + * registered because there is no way to synchronize the hardware + * registers between boot console code and regular console code. + */ + if (have_boot_console) + return; + + kt = kthread_run(nbcon_kthread_func, con, "pr/%s%d", con->name, con->index); + if (IS_ERR(kt)) { + con_printk(KERN_ERR, con, "failed to start printing thread\n"); + return; + } + + con->kthread = kt; + + /* + * It is important that console printing threads are scheduled + * shortly after a printk call and with generous runtime budgets. + */ + sched_set_normal(con->kthread, -20); +} + +static int __init printk_setup_threads(void) +{ + struct console *con; + + console_list_lock(); + printk_threads_enabled = true; + for_each_console(con) + nbcon_kthread_create(con); + if (force_printkthreads() && printing_via_unlock) + nbcon_legacy_kthread_create(); + console_list_unlock(); + return 0; +} +early_initcall(printk_setup_threads); + /** * nbcon_alloc - Allocate buffers needed by the nbcon console * @con: Console to allocate buffers for @ kernel/printk/nbcon.c:1594 @ bool nbcon_alloc(struct console *con) * * nbcon_alloc() *must* be called and succeed before this function * is called. - * - * This function expects that the legacy @con->seq has been set. */ void nbcon_init(struct console *con) { @ kernel/printk/nbcon.c:1602 @ void nbcon_init(struct console *con) /* nbcon_alloc() must have been called and successful! */ BUG_ON(!con->pbufs); - nbcon_seq_force(con, con->seq); + rcuwait_init(&con->rcuwait); + init_irq_work(&con->irq_work, nbcon_irq_work); + nbcon_seq_force(con, 0); + atomic_long_set(&ACCESS_PRIVATE(con, nbcon_prev_seq), -1UL); nbcon_state_set(con, &state); + nbcon_kthread_create(con); } /** @ kernel/printk/nbcon.c:1618 @ void nbcon_free(struct console *con) { struct nbcon_state state = { }; + nbcon_kthread_stop(con); nbcon_state_set(con, &state); /* Boot consoles share global printk buffers. */ @ kernel/printk/nbcon.c:1627 @ void nbcon_free(struct console *con) con->pbufs = NULL; } + +/** + * nbcon_driver_acquire - Acquire nbcon console and enter unsafe section + * @con: The nbcon console to acquire + * + * Context: Any context which could not be migrated to another CPU. + * + * Console drivers will usually use their own internal synchronization + * mechasism to synchronize between console printing and non-printing + * activities (such as setting baud rates). However, nbcon console drivers + * supporting atomic consoles may also want to mark unsafe sections when + * performing non-printing activities. + * + * This function acquires the nbcon console using priority NBCON_PRIO_NORMAL + * and marks it unsafe for handover/takeover. + * + * Console drivers using this function must have provided @nbcon_drvdata in + * their struct console, which is used to track ownership and state + * information. + */ +void nbcon_driver_acquire(struct console *con) +{ + struct nbcon_context *ctxt = &ACCESS_PRIVATE(con->nbcon_drvdata, ctxt); + + cant_migrate(); + + do { + do { + memset(ctxt, 0, sizeof(*ctxt)); + ctxt->console = con; + ctxt->prio = NBCON_PRIO_NORMAL; + } while (!nbcon_context_try_acquire(ctxt)); + + } while (!nbcon_context_enter_unsafe(ctxt)); +} +EXPORT_SYMBOL_GPL(nbcon_driver_acquire); + +/** + * nbcon_driver_release - Exit unsafe section and release the nbcon console + * @con: The nbcon console acquired in nbcon_driver_acquire() + */ +void nbcon_driver_release(struct console *con) +{ + struct nbcon_context *ctxt = &ACCESS_PRIVATE(con->nbcon_drvdata, ctxt); + + if (nbcon_context_exit_unsafe(ctxt)) + nbcon_context_release(ctxt); +} +EXPORT_SYMBOL_GPL(nbcon_driver_release); + +/** + * printk_kthread_shutdown - shutdown all threaded printers + * + * On system shutdown all threaded printers are stopped. This allows printk + * to transition back to atomic printing, thus providing a robust mechanism + * for the final shutdown/reboot messages to be output. + */ +static void printk_kthread_shutdown(void) +{ + struct console *con; + + console_list_lock(); + for_each_console(con) { + if (con->flags & CON_NBCON) + nbcon_kthread_stop(con); + } + console_list_unlock(); +} + +static struct syscore_ops printk_syscore_ops = { + .shutdown = printk_kthread_shutdown, +}; + +static int __init printk_init_ops(void) +{ + register_syscore_ops(&printk_syscore_ops); + return 0; +} +device_initcall(printk_init_ops); @ kernel/printk/printk.c:198 @ static int __init control_devkmsg(char *str) } __setup("printk.devkmsg=", control_devkmsg); +#if !defined(CONFIG_PREEMPT_RT) +DEFINE_STATIC_KEY_FALSE(force_printkthreads_key); + +static int __init setup_forced_printkthreads(char *arg) +{ + static_branch_enable(&force_printkthreads_key); + return 0; +} +early_param("threadprintk", setup_forced_printkthreads); +#endif + char devkmsg_log_str[DEVKMSG_STR_MAX_SIZE] = "ratelimit"; #if defined(CONFIG_PRINTK) && defined(CONFIG_SYSCTL) int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write, @ kernel/printk/printk.c:296 @ EXPORT_SYMBOL(console_list_unlock); * Return: A cookie to pass to console_srcu_read_unlock(). */ int console_srcu_read_lock(void) + __acquires(&console_srcu) { return srcu_read_lock_nmisafe(&console_srcu); } @ kernel/printk/printk.c:310 @ EXPORT_SYMBOL(console_srcu_read_lock); * Counterpart to console_srcu_read_lock() */ void console_srcu_read_unlock(int cookie) + __releases(&console_srcu) { srcu_read_unlock_nmisafe(&console_srcu, cookie); } @ kernel/printk/printk.c:477 @ static int console_msg_format = MSG_FORMAT_DEFAULT; /* syslog_lock protects syslog_* variables and write access to clear_seq. */ static DEFINE_MUTEX(syslog_lock); +/* + * Specifies if a legacy console is registered. If legacy consoles are + * present, it is necessary to perform the console lock/unlock dance + * whenever console flushing should occur. + */ +bool have_legacy_console; + +/* + * Specifies if an nbcon console is registered. If nbcon consoles are present, + * synchronous printing of legacy consoles will not occur during panic until + * the backtrace has been stored to the ringbuffer. + */ +static bool have_nbcon_console; + +/* + * Specifies if a boot console is registered. If boot consoles are present, + * nbcon consoles cannot print simultaneously and must be synchronized by + * the console lock. This is because boot consoles and nbcon consoles may + * have mapped the same hardware. + */ +bool have_boot_console; + #ifdef CONFIG_PRINTK DECLARE_WAIT_QUEUE_HEAD(log_wait); + +static DECLARE_WAIT_QUEUE_HEAD(legacy_wait); + /* All 3 protected by @syslog_lock. */ /* the next printk record to read by syslog(READ) or /proc/kmsg */ static u64 syslog_seq; @ kernel/printk/printk.c:1891 @ static bool console_waiter; * there may be a waiter spinning (like a spinlock). Also it must be * ready to hand over the lock at the end of the section. */ -static void console_lock_spinning_enable(void) +void console_lock_spinning_enable(void) { /* * Do not use spinning in panic(). The panic CPU wants to keep the lock. @ kernel/printk/printk.c:1930 @ static void console_lock_spinning_enable(void) * * Return: 1 if the lock rights were passed, 0 otherwise. */ -static int console_lock_spinning_disable_and_check(int cookie) +int console_lock_spinning_disable_and_check(int cookie) { int waiter; @ kernel/printk/printk.c:2341 @ int vprintk_store(int facility, int level, return ret; } +static bool legacy_allow_panic_sync; + +/* + * This acts as a one-way switch to allow legacy consoles to print from + * the printk() caller context on a panic CPU. It also attempts to flush + * the legacy consoles in this context. + */ +void printk_legacy_allow_panic_sync(void) +{ + legacy_allow_panic_sync = true; + + if (printing_via_unlock && !in_nmi()) { + if (console_trylock()) + console_unlock(); + } +} + asmlinkage int vprintk_emit(int facility, int level, const struct dev_printk_info *dev_info, const char *fmt, va_list args) { + bool do_trylock_unlock = printing_via_unlock && + !force_printkthreads(); int printed_len; - bool in_sched = false; /* Suppress unimportant messages after panic happens */ if (unlikely(suppress_printk)) @ kernel/printk/printk.c:2380 @ asmlinkage int vprintk_emit(int facility, int level, if (level == LOGLEVEL_SCHED) { level = LOGLEVEL_DEFAULT; - in_sched = true; + /* If called from the scheduler, we can not call up(). */ + do_trylock_unlock = false; } printk_delay(level); printed_len = vprintk_store(facility, level, dev_info, fmt, args); - /* If called from the scheduler, we can not call up(). */ - if (!in_sched) { + if (have_nbcon_console && !have_boot_console) { + bool is_panic_context = this_cpu_in_panic(); + + /* + * In panic, the legacy consoles are not allowed to print from + * the printk calling context unless explicitly allowed. This + * gives the safe nbcon consoles a chance to print out all the + * panic messages first. This restriction only applies if + * there are nbcon consoles registered. + */ + if (is_panic_context) + do_trylock_unlock &= legacy_allow_panic_sync; + + /* + * There are situations where nbcon atomic printing should + * happen in the printk() caller context: + * + * - When this CPU is in panic. + * + * - When booting, before the printing threads have been + * started. + * + * - During shutdown, since the printing threads may not get + * a chance to print the final messages. + * + * Note that if boot consoles are registered, the console + * lock/unlock dance must be relied upon instead because nbcon + * consoles cannot print simultaneously with boot consoles. + */ + if (is_panic_context || + !printk_threads_enabled || + (system_state > SYSTEM_RUNNING)) { + nbcon_atomic_flush_pending(); + } + } + + nbcon_wake_threads(); + + if (do_trylock_unlock) { /* * The caller may be holding system-critical or * timing-sensitive locks. Disable preemption during * printing of all remaining records to all consoles so that * this context can return as soon as possible. Hopefully * another printk() caller will take over the printing. + * + * Also, nbcon_get_default_prio() requires migration disabled. */ preempt_disable(); + /* * Try to acquire and then immediately release the console * semaphore. The release will print out buffers. With the * spinning variant, this context tries to take over the * printing from another printing context. + * + * Skip it in EMERGENCY priority. The console will be + * explicitly flushed when exiting the emergency section. */ - if (console_trylock_spinning()) - console_unlock(); + if (nbcon_get_default_prio() != NBCON_PRIO_EMERGENCY) { + if (console_trylock_spinning()) + console_unlock(); + } + preempt_enable(); } - if (in_sched) - defer_console_output(); - else + if (do_trylock_unlock) wake_up_klogd(); + else + defer_console_output(); return printed_len; } @ kernel/printk/printk.c:2486 @ EXPORT_SYMBOL(_printk); static bool pr_flush(int timeout_ms, bool reset_on_progress); static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress); +static struct task_struct *nbcon_legacy_kthread; + +static inline void wake_up_legacy_kthread(void) +{ + if (nbcon_legacy_kthread) + wake_up_interruptible(&legacy_wait); +} + #else /* CONFIG_PRINTK */ #define printk_time false @ kernel/printk/printk.c:2507 @ static u64 syslog_seq; static bool pr_flush(int timeout_ms, bool reset_on_progress) { return true; } static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress) { return true; } +static inline void nbcon_legacy_kthread_create(void) { } +static inline void wake_up_legacy_kthread(void) { } #endif /* CONFIG_PRINTK */ #ifdef CONFIG_EARLY_PRINTK @ kernel/printk/printk.c:2724 @ void suspend_console(void) void resume_console(void) { struct console *con; + short flags; + int cookie; if (!console_suspend_enabled) return; @ kernel/printk/printk.c:2742 @ void resume_console(void) */ synchronize_srcu(&console_srcu); + /* + * Since this runs in task context, wake the threaded printers + * directly rather than scheduling irq_work to do it. + */ + cookie = console_srcu_read_lock(); + for_each_console_srcu(con) { + flags = console_srcu_read_flags(con); + if (flags & CON_NBCON) + nbcon_kthread_wake(con); + } + console_srcu_read_unlock(cookie); + + wake_up_legacy_kthread(); + pr_flush(1000, true); } @ kernel/printk/printk.c:2770 @ void resume_console(void) */ static int console_cpu_notify(unsigned int cpu) { - if (!cpuhp_tasks_frozen) { + if (!cpuhp_tasks_frozen && printing_via_unlock && + !force_printkthreads()) { /* If trylock fails, someone else is doing the printing */ if (console_trylock()) console_unlock(); @ kernel/printk/printk.c:2828 @ int is_console_locked(void) } EXPORT_SYMBOL(is_console_locked); -/* - * Check if the given console is currently capable and allowed to print - * records. - * - * Requires the console_srcu_read_lock. - */ -static inline bool console_is_usable(struct console *con) -{ - short flags = console_srcu_read_flags(con); - - if (!(flags & CON_ENABLED)) - return false; - - if ((flags & CON_SUSPENDED)) - return false; - - if (!con->write) - return false; - - /* - * Console drivers may assume that per-cpu resources have been - * allocated. So unless they're explicitly marked as being able to - * cope (CON_ANYTIME) don't call them until this CPU is officially up. - */ - if (!cpu_online(raw_smp_processor_id()) && !(flags & CON_ANYTIME)) - return false; - - return true; -} - static void __console_unlock(void) { console_locked = 0; @ kernel/printk/printk.c:2837 @ static void __console_unlock(void) #ifdef CONFIG_PRINTK /* - * Prepend the message in @pmsg->pbufs->outbuf with a "dropped message". This - * is achieved by shifting the existing message over and inserting the dropped - * message. + * Prepend the message in @pmsg->pbufs->outbuf with the message in + * @pmsg->pbufs->scratchbuf. This is achieved by shifting the existing message + * over and inserting the scratchbuf message. * * @pmsg is the printk message to prepend. * - * @dropped is the dropped count to report in the dropped message. + * @len is the length of the message in @pmsg->pbufs->scratchbuf. * * If the message text in @pmsg->pbufs->outbuf does not have enough space for - * the dropped message, the message text will be sufficiently truncated. + * the scratchbuf message, the message text will be sufficiently truncated. * * If @pmsg->pbufs->outbuf is modified, @pmsg->outbuf_len is updated. */ -void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped) +static void __console_prepend_scratch(struct printk_message *pmsg, size_t len) { struct printk_buffers *pbufs = pmsg->pbufs; - const size_t scratchbuf_sz = sizeof(pbufs->scratchbuf); const size_t outbuf_sz = sizeof(pbufs->outbuf); char *scratchbuf = &pbufs->scratchbuf[0]; char *outbuf = &pbufs->outbuf[0]; - size_t len; - - len = scnprintf(scratchbuf, scratchbuf_sz, - "** %lu printk messages dropped **\n", dropped); /* * Make sure outbuf is sufficiently large before prepending. @ kernel/printk/printk.c:2877 @ void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped) pmsg->outbuf_len += len; } +/* + * Prepend the message in @pmsg->pbufs->outbuf with a "dropped message". + * @pmsg->outbuf_len is updated appropriately. + * + * @pmsg is the printk message to prepend. + * + * @dropped is the dropped count to report in the dropped message. + */ +void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped) +{ + struct printk_buffers *pbufs = pmsg->pbufs; + const size_t scratchbuf_sz = sizeof(pbufs->scratchbuf); + char *scratchbuf = &pbufs->scratchbuf[0]; + size_t len; + + len = scnprintf(scratchbuf, scratchbuf_sz, + "** %lu printk messages dropped **\n", dropped); + + __console_prepend_scratch(pmsg, len); +} + +/* + * Prepend the message in @pmsg->pbufs->outbuf with a "replay message". + * @pmsg->outbuf_len is updated appropriately. + * + * @pmsg is the printk message to prepend. + */ +void console_prepend_replay(struct printk_message *pmsg) +{ + struct printk_buffers *pbufs = pmsg->pbufs; + const size_t scratchbuf_sz = sizeof(pbufs->scratchbuf); + char *scratchbuf = &pbufs->scratchbuf[0]; + size_t len; + + len = scnprintf(scratchbuf, scratchbuf_sz, + "** replaying previous printk message **\n"); + + __console_prepend_scratch(pmsg, len); +} + /* * Read and format the specified record (or a later record if the specified * record is not available). @ kernel/printk/printk.c:2982 @ bool printk_get_next_message(struct printk_message *pmsg, u64 seq, return true; } +/* + * Legacy console printing from printk() caller context does not respect + * raw_spinlock/spinlock nesting. For !PREEMPT_RT the lockdep warning is a + * false positive. For PREEMPT_RT the false positive condition does not + * occur. + * + * This map is used to establish LD_WAIT_SLEEP context for the console write + * callbacks when legacy printing to avoid false positive lockdep complaints, + * thus allowing lockdep to continue to function for real issues. + */ +#ifdef CONFIG_PREEMPT_RT +static inline void printk_legacy_lock_map_acquire_try(void) { } +static inline void printk_legacy_lock_map_release(void) { } +#else +static DEFINE_WAIT_OVERRIDE_MAP(printk_legacy_map, LD_WAIT_SLEEP); + +static inline void printk_legacy_lock_map_acquire_try(void) +{ + lock_map_acquire_try(&printk_legacy_map); +} + +static inline void printk_legacy_lock_map_release(void) +{ + lock_map_release(&printk_legacy_map); +} +#endif /* CONFIG_PREEMPT_RT */ + /* * Used as the printk buffers for non-panic, serialized console printing. * This is for legacy (!CON_NBCON) as well as all boot (CON_BOOT) consoles. @ kernel/printk/printk.c:3058 @ static bool console_emit_next_record(struct console *con, bool *handover, int co con->dropped = 0; } - /* - * While actively printing out messages, if another printk() - * were to occur on another CPU, it may wait for this one to - * finish. This task can not be preempted if there is a - * waiter waiting to take over. - * - * Interrupts are disabled because the hand over to a waiter - * must not be interrupted until the hand over is completed - * (@console_waiter is cleared). - */ - printk_safe_enter_irqsave(flags); - console_lock_spinning_enable(); - - /* Do not trace print latency. */ - stop_critical_timings(); - /* Write everything out to the hardware. */ - con->write(con, outbuf, pmsg.outbuf_len); - start_critical_timings(); + if (force_printkthreads()) { + /* + * With forced threading this function is either in a thread + * or panic context. So there is no need for concern about + * printk reentrance, handovers, or lockdep complaints. + */ - con->seq = pmsg.seq + 1; + con->write(con, outbuf, pmsg.outbuf_len); + con->seq = pmsg.seq + 1; + } else { + /* + * While actively printing out messages, if another printk() + * were to occur on another CPU, it may wait for this one to + * finish. This task can not be preempted if there is a + * waiter waiting to take over. + * + * Interrupts are disabled because the hand over to a waiter + * must not be interrupted until the hand over is completed + * (@console_waiter is cleared). + */ + printk_safe_enter_irqsave(flags); + console_lock_spinning_enable(); - *handover = console_lock_spinning_disable_and_check(cookie); - printk_safe_exit_irqrestore(flags); + /* Do not trace print latency. */ + stop_critical_timings(); + + printk_legacy_lock_map_acquire_try(); + con->write(con, outbuf, pmsg.outbuf_len); + printk_legacy_lock_map_release(); + + start_critical_timings(); + + con->seq = pmsg.seq + 1; + + *handover = console_lock_spinning_disable_and_check(cookie); + printk_safe_exit_irqrestore(flags); + } skip: return true; } @ kernel/printk/printk.c:3149 @ static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handove cookie = console_srcu_read_lock(); for_each_console_srcu(con) { + short flags = console_srcu_read_flags(con); + u64 printk_seq; bool progress; - if (!console_is_usable(con)) + /* + * console_flush_all() is only for legacy consoles, + * unless the nbcon console has no kthread printer. + */ + if ((flags & CON_NBCON) && con->kthread) + continue; + + if (!console_is_usable(con, flags, !do_cond_resched)) continue; any_usable = true; - progress = console_emit_next_record(con, handover, cookie); + if (flags & CON_NBCON) { + progress = nbcon_legacy_emit_next_record(con, handover, cookie, + !do_cond_resched); + printk_seq = nbcon_seq_read(con); + } else { + progress = console_emit_next_record(con, handover, cookie); + printk_seq = con->seq; + } /* * If a handover has occurred, the SRCU read lock @ kernel/printk/printk.c:3181 @ static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handove return false; /* Track the next of the highest seq flushed. */ - if (con->seq > *next_seq) - *next_seq = con->seq; + if (printk_seq > *next_seq) + *next_seq = printk_seq; if (!progress) continue; @ kernel/printk/printk.c:3205 @ static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handove return false; } -/** - * console_unlock - unblock the console subsystem from printing - * - * Releases the console_lock which the caller holds to block printing of - * the console subsystem. - * - * While the console_lock was held, console output may have been buffered - * by printk(). If this is the case, console_unlock(); emits - * the output prior to releasing the lock. - * - * console_unlock(); may be called from any context. - */ -void console_unlock(void) +static void console_flush_and_unlock(void) { bool do_cond_resched; bool handover; @ kernel/printk/printk.c:3249 @ void console_unlock(void) */ } while (prb_read_valid(prb, next_seq, NULL) && console_trylock()); } + +/** + * console_unlock - unblock the console subsystem from printing + * + * Releases the console_lock which the caller holds to block printing of + * the console subsystem. + * + * While the console_lock was held, console output may have been buffered + * by printk(). If this is the case, console_unlock(); emits + * the output prior to releasing the lock. + * + * console_unlock(); may be called from any context. + */ +void console_unlock(void) +{ + /* + * Forced threading relies on kthread and atomic consoles for + * printing. It never attempts to print from console_unlock(). + */ + if (force_printkthreads()) { + __console_unlock(); + return; + } + + console_flush_and_unlock(); +} EXPORT_SYMBOL(console_unlock); /** @ kernel/printk/printk.c:3408 @ void console_flush_on_panic(enum con_flush_mode mode) console_srcu_read_unlock(cookie); } - console_flush_all(false, &next_seq, &handover); + nbcon_atomic_flush_pending(); + + if (printing_via_unlock) + console_flush_all(false, &next_seq, &handover); } /* @ kernel/printk/printk.c:3468 @ EXPORT_SYMBOL(console_stop); void console_start(struct console *console) { + short flags; + console_list_lock(); console_srcu_write_flags(console, console->flags | CON_ENABLED); + flags = console->flags; console_list_unlock(); + + /* + * Ensure that all SRCU list walks have completed. The related + * printing context must be able to see it is enabled so that + * it is guaranteed to wake up and resume printing. + */ + synchronize_srcu(&console_srcu); + + if (flags & CON_NBCON) + nbcon_kthread_wake(console); + else + wake_up_legacy_kthread(); + __pr_flush(console, 1000, true); } EXPORT_SYMBOL(console_start); +#ifdef CONFIG_PRINTK +static bool printer_should_wake(void) +{ + bool available = false; + struct console *con; + int cookie; + + if (kthread_should_stop()) + return true; + + cookie = console_srcu_read_lock(); + for_each_console_srcu(con) { + short flags = console_srcu_read_flags(con); + u64 printk_seq; + + /* + * The legacy printer thread is only for legacy consoles, + * unless the nbcon console has no kthread printer. + */ + if ((flags & CON_NBCON) && con->kthread) + continue; + + if (!console_is_usable(con, flags, true)) + continue; + + if (flags & CON_NBCON) { + printk_seq = nbcon_seq_read(con); + } else { + /* + * It is safe to read @seq because only this + * thread context updates @seq. + */ + printk_seq = con->seq; + } + + if (prb_read_valid(prb, printk_seq, NULL)) { + available = true; + break; + } + } + console_srcu_read_unlock(cookie); + + return available; +} + +static int nbcon_legacy_kthread_func(void *unused) +{ + int error; + + for (;;) { + error = wait_event_interruptible(legacy_wait, printer_should_wake()); + + if (kthread_should_stop()) + break; + + if (error) + continue; + + console_lock(); + console_flush_and_unlock(); + } + + return 0; +} + +void nbcon_legacy_kthread_create(void) +{ + struct task_struct *kt; + + lockdep_assert_held(&console_mutex); + + if (!force_printkthreads()) + return; + + if (!printk_threads_enabled || nbcon_legacy_kthread) + return; + + kt = kthread_run(nbcon_legacy_kthread_func, NULL, "pr/legacy"); + if (IS_ERR(kt)) { + pr_err("unable to start legacy printing thread\n"); + return; + } + + nbcon_legacy_kthread = kt; + + /* + * It is important that console printing threads are scheduled + * shortly after a printk call and with generous runtime budgets. + */ + sched_set_normal(nbcon_legacy_kthread, -20); +} +#endif /* CONFIG_PRINTK */ + static int __read_mostly keep_bootcon; static int __init keep_bootcon_setup(char *str) @ kernel/printk/printk.c:3682 @ static void try_enable_default_console(struct console *newcon) newcon->flags |= CON_CONSDEV; } +/* Set @newcon->seq to the first record this console should print. */ static void console_init_seq(struct console *newcon, bool bootcon_registered) { struct console *con; @ kernel/printk/printk.c:3731 @ static void console_init_seq(struct console *newcon, bool bootcon_registered) newcon->seq = prb_next_seq(prb); for_each_console(con) { - if ((con->flags & CON_BOOT) && - (con->flags & CON_ENABLED) && - con->seq < newcon->seq) { - newcon->seq = con->seq; + u64 seq; + + if (!((con->flags & CON_BOOT) && + (con->flags & CON_ENABLED))) { + continue; } + + if (con->flags & CON_NBCON) + seq = nbcon_seq_read(con); + else + seq = con->seq; + + if (seq < newcon->seq) + newcon->seq = seq; } } @ kernel/printk/printk.c:3782 @ void register_console(struct console *newcon) struct console *con; bool bootcon_registered = false; bool realcon_registered = false; + unsigned long flags; int err; console_list_lock(); @ kernel/printk/printk.c:3862 @ void register_console(struct console *newcon) newcon->dropped = 0; console_init_seq(newcon, bootcon_registered); - if (newcon->flags & CON_NBCON) + if (newcon->flags & CON_NBCON) { + have_nbcon_console = true; nbcon_init(newcon); + /* + * nbcon consoles have their own sequence counter. The legacy + * sequence counter is reset so that it is clear it is not + * being used. + */ + nbcon_seq_force(newcon, newcon->seq); + newcon->seq = 0; + } else { + have_legacy_console = true; + nbcon_legacy_kthread_create(); + } + + if (newcon->flags & CON_BOOT) + have_boot_console = true; + + /* + * If another context is actively using the hardware of this new + * console, it will not be aware of the nbcon synchronization. This + * is a risk that two contexts could access the hardware + * simultaneously if this new console is used for atomic printing + * and the other context is still using the hardware. + * + * Use the driver synchronization to ensure that the hardware is not + * in use while this new console transitions to being registered. + */ + if ((newcon->flags & CON_NBCON) && newcon->write_atomic) + newcon->device_lock(newcon, &flags); + /* * Put this console in the list - keep the * preferred driver at the head of the list. @ kernel/printk/printk.c:3918 @ void register_console(struct console *newcon) * register_console() completes. */ + /* This new console is now registered. */ + if ((newcon->flags & CON_NBCON) && newcon->write_atomic) + newcon->device_unlock(newcon, flags); + console_sysfs_notify(); /* @ kernel/printk/printk.c:3950 @ EXPORT_SYMBOL(register_console); /* Must be called under console_list_lock(). */ static int unregister_console_locked(struct console *console) { + bool is_boot_con = (console->flags & CON_BOOT); + bool found_legacy_con = false; + bool found_nbcon_con = false; + bool found_boot_con = false; + struct console *c; int res; lockdep_assert_console_list_lock_held(); @ kernel/printk/printk.c:4002 @ static int unregister_console_locked(struct console *console) if (console->exit) res = console->exit(console); + /* + * With this console gone, the global flags tracking registered + * console types may have changed. Update them. + */ + for_each_console(c) { + if (c->flags & CON_BOOT) + found_boot_con = true; + + if (c->flags & CON_NBCON) + found_nbcon_con = true; + else + found_legacy_con = true; + } + if (!found_boot_con) + have_boot_console = found_boot_con; + if (!found_legacy_con) + have_legacy_console = found_legacy_con; + if (!found_nbcon_con) + have_nbcon_console = found_nbcon_con; + + /* + * When the last boot console unregisters, start up the + * printing threads. + */ + if (is_boot_con && !have_boot_console) { + for_each_console(c) + nbcon_kthread_create(c); + } + +#ifdef CONFIG_PRINTK + if (!printing_via_unlock && nbcon_legacy_kthread) { + kthread_stop(nbcon_legacy_kthread); + nbcon_legacy_kthread = NULL; + } +#endif + return res; } @ kernel/printk/printk.c:4196 @ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre seq = prb_next_reserve_seq(prb); - /* Flush the consoles so that records up to @seq are printed. */ - console_lock(); - console_unlock(); + /* + * Flush the consoles so that records up to @seq are printed. + * Otherwise this function will just wait for the threaded printers + * to print up to @seq. + */ + if (printing_via_unlock && !force_printkthreads()) { + console_lock(); + console_unlock(); + } for (;;) { unsigned long begin_jiffies; unsigned long slept_jiffies; + bool use_console_lock = printing_via_unlock; + + /* + * Ensure the compiler does not optimize @use_console_lock to + * be @printing_via_unlock since the latter can change at any + * time. + */ + barrier(); diff = 0; - /* - * Hold the console_lock to guarantee safe access to - * console->seq. Releasing console_lock flushes more - * records in case @seq is still not printed on all - * usable consoles. - */ - console_lock(); + if (use_console_lock) { + /* + * Hold the console_lock to guarantee safe access to + * console->seq. Releasing console_lock flushes more + * records in case @seq is still not printed on all + * usable consoles. + */ + console_lock(); + } cookie = console_srcu_read_lock(); for_each_console_srcu(c) { @ kernel/printk/printk.c:4242 @ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre * that they make forward progress, so only increment * @diff for usable consoles. */ - if (!console_is_usable(c)) + if (!console_is_usable(c, flags, true) && + !console_is_usable(c, flags, false)) { continue; + } if (flags & CON_NBCON) { printk_seq = nbcon_seq_read(c); } else { + WARN_ON_ONCE(!use_console_lock); printk_seq = c->seq; } @ kernel/printk/printk.c:4262 @ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre if (diff != last_diff && reset_on_progress) remaining_jiffies = timeout_jiffies; - console_unlock(); + if (use_console_lock) + console_unlock(); /* Note: @diff is 0 if there are no usable consoles. */ if (diff == 0 || remaining_jiffies == 0) @ kernel/printk/printk.c:4315 @ static void wake_up_klogd_work_func(struct irq_work *irq_work) int pending = this_cpu_xchg(printk_pending, 0); if (pending & PRINTK_PENDING_OUTPUT) { - /* If trylock fails, someone else is doing the printing */ - if (console_trylock()) - console_unlock(); + if (force_printkthreads()) { + wake_up_legacy_kthread(); + } else { + /* + * If trylock fails, some other context + * will do the printing. + */ + if (console_trylock()) + console_unlock(); + } } if (pending & PRINTK_PENDING_WAKEUP) @ kernel/printk/printk.c:4340 @ static void __wake_up_klogd(int val) return; preempt_disable(); + /* * Guarantee any new records can be seen by tasks preparing to wait * before this context checks if the wait queue is empty. @ kernel/printk/printk.c:4352 @ static void __wake_up_klogd(int val) * * This pairs with devkmsg_read:A and syslog_print:A. */ - if (wq_has_sleeper(&log_wait) || /* LMM(__wake_up_klogd:A) */ - (val & PRINTK_PENDING_OUTPUT)) { + if (!wq_has_sleeper(&log_wait)) /* LMM(__wake_up_klogd:A) */ + val &= ~PRINTK_PENDING_WAKEUP; + + /* + * Simple read is safe. register_console() would flush a newly + * registered legacy console when writing the message about it + * being enabled. + */ + if (!printing_via_unlock) + val &= ~PRINTK_PENDING_OUTPUT; + + if (val) { this_cpu_or(printk_pending, val); irq_work_queue(this_cpu_ptr(&wake_up_klogd_work)); } + preempt_enable(); } @ kernel/printk/printk.c:4409 @ void defer_console_output(void) void printk_trigger_flush(void) { + nbcon_wake_threads(); defer_console_output(); } @ kernel/printk/printk_ringbuffer.h:8 @ #include <linux/atomic.h> #include <linux/dev_printk.h> +#include <linux/stddef.h> +#include <linux/types.h> /* * Meta information about each stored message. @ kernel/printk/printk_safe.c:29 @ void __printk_safe_exit(void) this_cpu_dec(printk_context); } +void __printk_deferred_enter(void) +{ + cant_migrate(); + __printk_safe_enter(); +} + +void __printk_deferred_exit(void) +{ + cant_migrate(); + __printk_safe_exit(); +} + asmlinkage int vprintk(const char *fmt, va_list args) { #ifdef CONFIG_KGDB_KDB @ kernel/rcu/rcutorture.c:2416 @ static int rcutorture_booster_init(unsigned int cpu) WARN_ON_ONCE(!t); sp.sched_priority = 2; sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); +#ifdef CONFIG_PREEMPT_RT + t = per_cpu(timersd, cpu); + WARN_ON_ONCE(!t); + sp.sched_priority = 2; + sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); +#endif } /* Don't allow time recalculation while creating a new task. */ @ kernel/rcu/tree_exp.h:10 @ * Authors: Paul E. McKenney <paulmck@linux.ibm.com> */ +#include <linux/console.h> #include <linux/lockdep.h> static void rcu_exp_handler(void *unused); @ kernel/rcu/tree_exp.h:575 @ static void synchronize_rcu_expedited_wait(void) return; if (rcu_stall_is_suppressed()) continue; + + nbcon_cpu_emergency_enter(); + j = jiffies; rcu_stall_notifier_call_chain(RCU_STALL_NOTIFY_EXP, (void *)(j - jiffies_start)); trace_rcu_stall_warning(rcu_state.name, TPS("ExpeditedStall")); @ kernel/rcu/tree_exp.h:631 @ static void synchronize_rcu_expedited_wait(void) rcu_exp_print_detail_task_stall_rnp(rnp); } jiffies_stall = 3 * rcu_exp_jiffies_till_stall_check() + 3; + + nbcon_cpu_emergency_exit(); + panic_on_rcu_stall(); } } @ kernel/rcu/tree_stall.h:10 @ * Author: Paul E. McKenney <paulmck@linux.ibm.com> */ +#include <linux/console.h> #include <linux/kvm_para.h> #include <linux/rcu_notifier.h> @ kernel/rcu/tree_stall.h:608 @ static void print_other_cpu_stall(unsigned long gp_seq, unsigned long gps) if (rcu_stall_is_suppressed()) return; + nbcon_cpu_emergency_enter(); + /* * OK, time to rat on our buddy... * See Documentation/RCU/stallwarn.rst for info on how to debug @ kernel/rcu/tree_stall.h:661 @ static void print_other_cpu_stall(unsigned long gp_seq, unsigned long gps) rcu_check_gp_kthread_expired_fqs_timer(); rcu_check_gp_kthread_starvation(); + nbcon_cpu_emergency_exit(); + panic_on_rcu_stall(); rcu_force_quiescent_state(); /* Kick them all. */ @ kernel/rcu/tree_stall.h:683 @ static void print_cpu_stall(unsigned long gps) if (rcu_stall_is_suppressed()) return; + nbcon_cpu_emergency_enter(); + /* * OK, time to rat on ourselves... * See Documentation/RCU/stallwarn.rst for info on how to debug @ kernel/rcu/tree_stall.h:713 @ static void print_cpu_stall(unsigned long gps) jiffies + 3 * rcu_jiffies_till_stall_check() + 3); raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + nbcon_cpu_emergency_exit(); + panic_on_rcu_stall(); /* @ kernel/sched/core.c:902 @ static inline void hrtick_rq_init(struct rq *rq) #if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG) /* - * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG, + * Atomically set TIF_NEED_RESCHED[_LAZY] and test for TIF_POLLING_NRFLAG, * this avoids any races wrt polling state changes and thereby avoids * spurious IPIs. */ -static inline bool set_nr_and_not_polling(struct task_struct *p) +static inline bool set_nr_and_not_polling(struct task_struct *p, int tif_bit) { struct thread_info *ti = task_thread_info(p); - return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG); + + return !(fetch_or(&ti->flags, 1 << tif_bit) & _TIF_POLLING_NRFLAG); } /* @ kernel/sched/core.c:927 @ static bool set_nr_if_polling(struct task_struct *p) do { if (!(val & _TIF_POLLING_NRFLAG)) return false; - if (val & _TIF_NEED_RESCHED) + if (val & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)) return true; } while (!try_cmpxchg(&ti->flags, &val, val | _TIF_NEED_RESCHED)); @ kernel/sched/core.c:935 @ static bool set_nr_if_polling(struct task_struct *p) } #else -static inline bool set_nr_and_not_polling(struct task_struct *p) +static inline bool set_nr_and_not_polling(struct task_struct *p, int tif_bit) { - set_tsk_need_resched(p); + set_tsk_thread_flag(p, tif_bit); return true; } @ kernel/sched/core.c:1042 @ void wake_up_q(struct wake_q_head *head) * might also involve a cross-CPU call to trigger the scheduler on * the target CPU. */ -void resched_curr(struct rq *rq) +static void __resched_curr(struct rq *rq, int lazy) { + int cpu, tif_bit = TIF_NEED_RESCHED + lazy; struct task_struct *curr = rq->curr; - int cpu; lockdep_assert_rq_held(rq); - if (test_tsk_need_resched(curr)) + if (unlikely(test_tsk_thread_flag(curr, tif_bit))) return; cpu = cpu_of(rq); if (cpu == smp_processor_id()) { - set_tsk_need_resched(curr); - set_preempt_need_resched(); + set_tsk_thread_flag(curr, tif_bit); + if (!lazy) + set_preempt_need_resched(); return; } - if (set_nr_and_not_polling(curr)) - smp_send_reschedule(cpu); - else + if (set_nr_and_not_polling(curr, tif_bit)) { + if (!lazy) + smp_send_reschedule(cpu); + } else { trace_sched_wake_idle_without_ipi(cpu); + } +} + +void resched_curr(struct rq *rq) +{ + __resched_curr(rq, 0); +} + +void resched_curr_lazy(struct rq *rq) +{ + int lazy = IS_ENABLED(CONFIG_PREEMPT_BUILD_AUTO) && !sched_feat(FORCE_NEED_RESCHED) ? + TIF_NEED_RESCHED_LAZY_OFFSET : 0; + + if (lazy && unlikely(test_tsk_thread_flag(rq->curr, TIF_NEED_RESCHED))) + return; + + __resched_curr(rq, lazy); } void resched_cpu(int cpu) @ kernel/sched/core.c:1177 @ static void wake_up_idle_cpu(int cpu) * and testing of the above solutions didn't appear to report * much benefits. */ - if (set_nr_and_not_polling(rq->idle)) + if (set_nr_and_not_polling(rq->idle, TIF_NEED_RESCHED)) smp_send_reschedule(cpu); else trace_sched_wake_idle_without_ipi(cpu); @ kernel/sched/core.c:8934 @ static inline void preempt_dynamic_init(void) { } #endif /* #ifdef CONFIG_PREEMPT_DYNAMIC */ +/* + * task_is_pi_boosted - Check if task has been PI boosted. + * @p: Task to check. + * + * Return true if task is subject to priority inheritance. + */ +bool task_is_pi_boosted(const struct task_struct *p) +{ + int prio = p->prio; + + if (!rt_prio(prio)) + return false; + return prio != p->normal_prio; +} + /** * yield - yield the current processor to other threads. * @ kernel/sched/debug.c:336 @ static const struct file_operations sched_debug_fops = { .release = seq_release, }; +static ssize_t sched_hog_write(struct file *filp, const char __user *ubuf, + size_t cnt, loff_t *ppos) +{ + unsigned long end = jiffies + 60 * HZ; + + for (; time_before(jiffies, end) && !signal_pending(current);) + cpu_relax(); + + return cnt; +} + +static const struct file_operations sched_hog_fops = { + .write = sched_hog_write, + .open = simple_open, + .llseek = default_llseek, +}; + static struct dentry *debugfs_sched; static __init int sched_init_debug(void) @ kernel/sched/debug.c:394 @ static __init int sched_init_debug(void) debugfs_create_file("debug", 0444, debugfs_sched, NULL, &sched_debug_fops); + debugfs_create_file("hog", 0200, debugfs_sched, NULL, &sched_hog_fops); + return 0; } late_initcall(sched_init_debug); @ kernel/sched/fair.c:978 @ static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se); * XXX: strictly: vd_i += N*r_i/w_i such that: vd_i > ve_i * this is probably good enough. */ -static void update_deadline(struct cfs_rq *cfs_rq, struct sched_entity *se) +static void update_deadline(struct cfs_rq *cfs_rq, struct sched_entity *se, bool tick) { + struct rq *rq = rq_of(cfs_rq); + if ((s64)(se->vruntime - se->deadline) < 0) return; @ kernel/sched/fair.c:1000 @ static void update_deadline(struct cfs_rq *cfs_rq, struct sched_entity *se) /* * The task has consumed its request, reschedule. */ - if (cfs_rq->nr_running > 1) { - resched_curr(rq_of(cfs_rq)); - clear_buddies(cfs_rq, se); + if (cfs_rq->nr_running < 2) + return; + + if (!IS_ENABLED(CONFIG_PREEMPT_BUILD_AUTO) || sched_feat(FORCE_NEED_RESCHED)) { + resched_curr(rq); + } else { + /* Did the task ignore the lazy reschedule request? */ + if (tick && test_tsk_thread_flag(rq->curr, TIF_NEED_RESCHED_LAZY)) + resched_curr(rq); + else + resched_curr_lazy(rq); } + clear_buddies(cfs_rq, se); } #include "pelt.h" @ kernel/sched/fair.c:1167 @ s64 update_curr_common(struct rq *rq) /* * Update the current task's runtime statistics. */ -static void update_curr(struct cfs_rq *cfs_rq) +static void __update_curr(struct cfs_rq *cfs_rq, bool tick) { struct sched_entity *curr = cfs_rq->curr; s64 delta_exec; @ kernel/sched/fair.c:1180 @ static void update_curr(struct cfs_rq *cfs_rq) return; curr->vruntime += calc_delta_fair(delta_exec, curr); - update_deadline(cfs_rq, curr); + update_deadline(cfs_rq, curr, tick); update_min_vruntime(cfs_rq); if (entity_is_task(curr)) @ kernel/sched/fair.c:1189 @ static void update_curr(struct cfs_rq *cfs_rq) account_cfs_rq_runtime(cfs_rq, delta_exec); } +static inline void update_curr(struct cfs_rq *cfs_rq) +{ + __update_curr(cfs_rq, false); +} + static void update_curr_fair(struct rq *rq) { update_curr(cfs_rq_of(&rq->curr->se)); @ kernel/sched/fair.c:5518 @ entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued) /* * Update run-time statistics of the 'current'. */ - update_curr(cfs_rq); + __update_curr(cfs_rq, true); /* * Ensure that runnable average is periodically updated. @ kernel/sched/fair.c:5532 @ entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued) * validating it and just reschedule. */ if (queued) { - resched_curr(rq_of(cfs_rq)); + resched_curr_lazy(rq_of(cfs_rq)); return; } /* @ kernel/sched/fair.c:5678 @ static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) * hierarchy can be throttled */ if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr)) - resched_curr(rq_of(cfs_rq)); + resched_curr_lazy(rq_of(cfs_rq)); } static __always_inline @ kernel/sched/fair.c:5938 @ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq) /* Determine whether we need to wake up potentially idle CPU: */ if (rq->curr == rq->idle && rq->cfs.nr_running) - resched_curr(rq); + resched_curr_lazy(rq); } #ifdef CONFIG_SMP @ kernel/sched/fair.c:6653 @ static void hrtick_start_fair(struct rq *rq, struct task_struct *p) if (delta < 0) { if (task_current(rq, p)) - resched_curr(rq); + resched_curr_lazy(rq); return; } hrtick_start(rq, delta); @ kernel/sched/fair.c:8329 @ static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int * prevents us from potentially nominating it as a false LAST_BUDDY * below. */ - if (test_tsk_need_resched(curr)) + if (need_resched()) return; /* Idle tasks are by definition preempted by non-idle tasks. */ @ kernel/sched/fair.c:8371 @ static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int return; preempt: - resched_curr(rq); + resched_curr_lazy(rq); } #ifdef CONFIG_SMP @ kernel/sched/fair.c:12517 @ static inline void task_tick_core(struct rq *rq, struct task_struct *curr) */ if (rq->core->core_forceidle_count && rq->cfs.nr_running == 1 && __entity_slice_used(&curr->se, MIN_NR_TASKS_DURING_FORCEIDLE)) - resched_curr(rq); + resched_curr_lazy(rq); } /* @ kernel/sched/fair.c:12682 @ prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio) */ if (task_current(rq, p)) { if (p->prio > oldprio) - resched_curr(rq); + resched_curr_lazy(rq); } else wakeup_preempt(rq, p, 0); } @ kernel/sched/features.h:90 @ SCHED_FEAT(UTIL_EST, true) SCHED_FEAT(LATENCY_WARN, false) SCHED_FEAT(HZ_BW, true) + +SCHED_FEAT(FORCE_NEED_RESCHED, false) @ kernel/sched/idle.c:60 @ static noinline int __cpuidle cpu_idle_poll(void) ct_cpuidle_enter(); raw_local_irq_enable(); - while (!tif_need_resched() && - (cpu_idle_force_poll || tick_check_broadcast_expired())) + while (!need_resched() && (cpu_idle_force_poll || tick_check_broadcast_expired())) cpu_relax(); raw_local_irq_disable(); @ kernel/sched/rt.c:2197 @ static int rto_next_cpu(struct root_domain *rd) rd->rto_cpu = cpu; - if (cpu < nr_cpu_ids) + if (cpu < nr_cpu_ids) { + if (!has_pushable_tasks(cpu_rq(cpu))) + continue; return cpu; + } rd->rto_cpu = -1; @ kernel/sched/sched.h:2466 @ extern void init_sched_fair_class(void); extern void reweight_task(struct task_struct *p, int prio); extern void resched_curr(struct rq *rq); +extern void resched_curr_lazy(struct rq *rq); extern void resched_cpu(int cpu); extern struct rt_bandwidth def_rt_bandwidth; @ kernel/softirq.c:251 @ void __local_bh_enable_ip(unsigned long ip, unsigned int cnt) } EXPORT_SYMBOL(__local_bh_enable_ip); +void softirq_preempt(void) +{ + if (WARN_ON_ONCE(!preemptible())) + return; + + if (WARN_ON_ONCE(__this_cpu_read(softirq_ctrl.cnt) != SOFTIRQ_OFFSET)) + return; + + __local_bh_enable(SOFTIRQ_OFFSET, true); + /* preemption point */ + __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET); +} + /* * Invoked from ksoftirqd_run() outside of the interrupt disabled section * to acquire the per CPU local lock for reentrancy protection. @ kernel/softirq.c:636 @ static inline void tick_irq_exit(void) #endif } +#ifdef CONFIG_PREEMPT_RT +DEFINE_PER_CPU(struct task_struct *, timersd); +DEFINE_PER_CPU(unsigned long, pending_timer_softirq); + +static void wake_timersd(void) +{ + struct task_struct *tsk = __this_cpu_read(timersd); + + if (tsk) + wake_up_process(tsk); +} + +#else + +static inline void wake_timersd(void) { } + +#endif + static inline void __irq_exit_rcu(void) { #ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED @ kernel/softirq.c:666 @ static inline void __irq_exit_rcu(void) if (!in_interrupt() && local_softirq_pending()) invoke_softirq(); + if (IS_ENABLED(CONFIG_PREEMPT_RT) && local_pending_timers() && + !(in_nmi() | in_hardirq())) + wake_timersd(); + tick_irq_exit(); } @ kernel/softirq.c:1006 @ static struct smp_hotplug_thread softirq_threads = { .thread_comm = "ksoftirqd/%u", }; +#ifdef CONFIG_PREEMPT_RT +static void timersd_setup(unsigned int cpu) +{ + sched_set_fifo_low(current); +} + +static int timersd_should_run(unsigned int cpu) +{ + return local_pending_timers(); +} + +static void run_timersd(unsigned int cpu) +{ + unsigned int timer_si; + + ksoftirqd_run_begin(); + + timer_si = local_pending_timers(); + __this_cpu_write(pending_timer_softirq, 0); + or_softirq_pending(timer_si); + + __do_softirq(); + + ksoftirqd_run_end(); +} + +static void raise_ktimers_thread(unsigned int nr) +{ + trace_softirq_raise(nr); + __this_cpu_or(pending_timer_softirq, 1 << nr); +} + +void raise_hrtimer_softirq(void) +{ + raise_ktimers_thread(HRTIMER_SOFTIRQ); +} + +void raise_timer_softirq(void) +{ + unsigned long flags; + + local_irq_save(flags); + raise_ktimers_thread(TIMER_SOFTIRQ); + wake_timersd(); + local_irq_restore(flags); +} + +static struct smp_hotplug_thread timer_threads = { + .store = &timersd, + .setup = timersd_setup, + .thread_should_run = timersd_should_run, + .thread_fn = run_timersd, + .thread_comm = "ktimers/%u", +}; +#endif + static __init int spawn_ksoftirqd(void) { cpuhp_setup_state_nocalls(CPUHP_SOFTIRQ_DEAD, "softirq:dead", NULL, takeover_tasklets); BUG_ON(smpboot_register_percpu_thread(&softirq_threads)); - +#ifdef CONFIG_PREEMPT_RT + BUG_ON(smpboot_register_percpu_thread(&timer_threads)); +#endif return 0; } early_initcall(spawn_ksoftirqd); @ kernel/time/hrtimer.c:1815 @ void hrtimer_interrupt(struct clock_event_device *dev) if (!ktime_before(now, cpu_base->softirq_expires_next)) { cpu_base->softirq_expires_next = KTIME_MAX; cpu_base->softirq_activated = 1; - raise_softirq_irqoff(HRTIMER_SOFTIRQ); + raise_hrtimer_softirq(); } __hrtimer_run_queues(cpu_base, now, flags, HRTIMER_ACTIVE_HARD); @ kernel/time/hrtimer.c:1928 @ void hrtimer_run_queues(void) if (!ktime_before(now, cpu_base->softirq_expires_next)) { cpu_base->softirq_expires_next = KTIME_MAX; cpu_base->softirq_activated = 1; - raise_softirq_irqoff(HRTIMER_SOFTIRQ); + raise_hrtimer_softirq(); } __hrtimer_run_queues(cpu_base, now, flags, HRTIMER_ACTIVE_HARD); @ kernel/time/tick-sched.c:858 @ static void tick_nohz_restart(struct tick_sched *ts, ktime_t now) static inline bool local_timer_softirq_pending(void) { - return local_softirq_pending() & BIT(TIMER_SOFTIRQ); + return local_pending_timers() & BIT(TIMER_SOFTIRQ); } /* @ kernel/time/timer.c:1566 @ static inline void timer_base_unlock_expiry(struct timer_base *base) */ static void timer_sync_wait_running(struct timer_base *base) { - if (atomic_read(&base->timer_waiters)) { + bool need_preempt; + + need_preempt = task_is_pi_boosted(current); + if (need_preempt || atomic_read(&base->timer_waiters)) { raw_spin_unlock_irq(&base->lock); spin_unlock(&base->expiry_lock); + + if (need_preempt) + softirq_preempt(); + spin_lock(&base->expiry_lock); raw_spin_lock_irq(&base->lock); } @ kernel/time/timer.c:2476 @ static void run_local_timers(void) /* Raise the softirq only if required. */ if (time_after_eq(jiffies, base->next_expiry) || (i == BASE_DEF && tmigr_requires_handle_remote())) { - raise_softirq(TIMER_SOFTIRQ); + raise_timer_softirq(); return; } } @ kernel/trace/trace.c:2516 @ unsigned int tracing_gen_ctx_irq_test(unsigned int irqs_status) if (tif_need_resched()) trace_flags |= TRACE_FLAG_NEED_RESCHED; + if (tif_need_resched_lazy()) + trace_flags |= TRACE_FLAG_NEED_RESCHED_LAZY; if (test_preempt_need_resched()) trace_flags |= TRACE_FLAG_PREEMPT_RESCHED; return (trace_flags << 16) | (min_t(unsigned int, pc & 0xff, 0xf)) | @ kernel/trace/trace_output.c:463 @ int trace_print_lat_fmt(struct trace_seq *s, struct trace_entry *entry) (entry->flags & TRACE_FLAG_IRQS_OFF && bh_off) ? 'D' : (entry->flags & TRACE_FLAG_IRQS_OFF) ? 'd' : bh_off ? 'b' : - (entry->flags & TRACE_FLAG_IRQS_NOSUPPORT) ? 'X' : + !IS_ENABLED(CONFIG_TRACE_IRQFLAGS_SUPPORT) ? 'X' : '.'; - switch (entry->flags & (TRACE_FLAG_NEED_RESCHED | + switch (entry->flags & (TRACE_FLAG_NEED_RESCHED | TRACE_FLAG_NEED_RESCHED_LAZY | TRACE_FLAG_PREEMPT_RESCHED)) { + case TRACE_FLAG_NEED_RESCHED | TRACE_FLAG_NEED_RESCHED_LAZY | TRACE_FLAG_PREEMPT_RESCHED: + need_resched = 'B'; + break; case TRACE_FLAG_NEED_RESCHED | TRACE_FLAG_PREEMPT_RESCHED: need_resched = 'N'; break; + case TRACE_FLAG_NEED_RESCHED_LAZY | TRACE_FLAG_PREEMPT_RESCHED: + need_resched = 'L'; + break; + case TRACE_FLAG_NEED_RESCHED | TRACE_FLAG_NEED_RESCHED_LAZY: + need_resched = 'b'; + break; case TRACE_FLAG_NEED_RESCHED: need_resched = 'n'; break; + case TRACE_FLAG_NEED_RESCHED_LAZY: + need_resched = 'l'; + break; case TRACE_FLAG_PREEMPT_RESCHED: need_resched = 'p'; break; @ localversion-rt:1 @ +-rt1 @ net/core/dev.c:81 @ #include <linux/slab.h> #include <linux/sched.h> #include <linux/sched/mm.h> +#include <linux/smpboot.h> #include <linux/mutex.h> #include <linux/rwsem.h> #include <linux/string.h> @ net/core/dev.c:201 @ static inline struct hlist_head *dev_index_hash(struct net *net, int ifindex) return &net->dev_index_head[ifindex & (NETDEV_HASHENTRIES - 1)]; } -static inline void rps_lock_irqsave(struct softnet_data *sd, - unsigned long *flags) +#ifndef CONFIG_PREEMPT_RT + +static DEFINE_STATIC_KEY_FALSE(use_backlog_threads_key); + +static int __init setup_backlog_napi_threads(char *arg) { - if (IS_ENABLED(CONFIG_RPS)) + static_branch_enable(&use_backlog_threads_key); + return 0; +} +early_param("thread_backlog_napi", setup_backlog_napi_threads); + +static bool use_backlog_threads(void) +{ + return static_branch_unlikely(&use_backlog_threads_key); +} + +#else + +static bool use_backlog_threads(void) +{ + return true; +} + +#endif + +static inline void backlog_lock_irq_save(struct softnet_data *sd, + unsigned long *flags) +{ + if (IS_ENABLED(CONFIG_RPS) || use_backlog_threads()) spin_lock_irqsave(&sd->input_pkt_queue.lock, *flags); else if (!IS_ENABLED(CONFIG_PREEMPT_RT)) local_irq_save(*flags); } -static inline void rps_lock_irq_disable(struct softnet_data *sd) +static inline void backlog_lock_irq_disable(struct softnet_data *sd) { - if (IS_ENABLED(CONFIG_RPS)) + if (IS_ENABLED(CONFIG_RPS) || use_backlog_threads()) spin_lock_irq(&sd->input_pkt_queue.lock); else if (!IS_ENABLED(CONFIG_PREEMPT_RT)) local_irq_disable(); } -static inline void rps_unlock_irq_restore(struct softnet_data *sd, - unsigned long *flags) +static inline void backlog_unlock_irq_restore(struct softnet_data *sd, + unsigned long *flags) { - if (IS_ENABLED(CONFIG_RPS)) + if (IS_ENABLED(CONFIG_RPS) || use_backlog_threads()) spin_unlock_irqrestore(&sd->input_pkt_queue.lock, *flags); else if (!IS_ENABLED(CONFIG_PREEMPT_RT)) local_irq_restore(*flags); } -static inline void rps_unlock_irq_enable(struct softnet_data *sd) +static inline void backlog_unlock_irq_enable(struct softnet_data *sd) { - if (IS_ENABLED(CONFIG_RPS)) + if (IS_ENABLED(CONFIG_RPS) || use_backlog_threads()) spin_unlock_irq(&sd->input_pkt_queue.lock); else if (!IS_ENABLED(CONFIG_PREEMPT_RT)) local_irq_enable(); @ net/core/dev.c:4433 @ EXPORT_SYMBOL(__dev_direct_xmit); /************************************************************************* * Receiver routines *************************************************************************/ +static DEFINE_PER_CPU(struct task_struct *, backlog_napi); unsigned int sysctl_skb_defer_max __read_mostly = 64; int weight_p __read_mostly = 64; /* old backlog weight */ @ net/core/dev.c:4457 @ static inline void ____napi_schedule(struct softnet_data *sd, */ thread = READ_ONCE(napi->thread); if (thread) { - /* Avoid doing set_bit() if the thread is in - * INTERRUPTIBLE state, cause napi_thread_wait() - * makes sure to proceed with napi polling - * if the thread is explicitly woken from here. - */ - if (READ_ONCE(thread->__state) != TASK_INTERRUPTIBLE) - set_bit(NAPI_STATE_SCHED_THREADED, &napi->state); + if (use_backlog_threads() && thread == raw_cpu_read(backlog_napi)) + goto use_local_napi; + + set_bit(NAPI_STATE_SCHED_THREADED, &napi->state); wake_up_process(thread); return; } } +use_local_napi: list_add_tail(&napi->poll_list, &sd->poll_list); WRITE_ONCE(napi->list_owner, smp_processor_id()); /* If not called from net_rx_action() @ net/core/dev.c:4706 @ static void napi_schedule_rps(struct softnet_data *sd) #ifdef CONFIG_RPS if (sd != mysd) { + if (use_backlog_threads()) { + __napi_schedule_irqoff(&sd->backlog); + return; + } + sd->rps_ipi_next = mysd->rps_ipi_list; mysd->rps_ipi_list = sd; @ net/core/dev.c:4725 @ static void napi_schedule_rps(struct softnet_data *sd) __napi_schedule_irqoff(&mysd->backlog); } +void kick_defer_list_purge(struct softnet_data *sd, unsigned int cpu) +{ + unsigned long flags; + + if (use_backlog_threads()) { + backlog_lock_irq_save(sd, &flags); + + if (!__test_and_set_bit(NAPI_STATE_SCHED, &sd->backlog.state)) + __napi_schedule_irqoff(&sd->backlog); + + backlog_unlock_irq_restore(sd, &flags); + + } else if (!cmpxchg(&sd->defer_ipi_scheduled, 0, 1)) { + smp_call_function_single_async(cpu, &sd->defer_csd); + } +} + #ifdef CONFIG_NET_FLOW_LIMIT int netdev_flow_limit_table_len __read_mostly = (1 << 12); #endif @ net/core/dev.c:4797 @ static int enqueue_to_backlog(struct sk_buff *skb, int cpu, reason = SKB_DROP_REASON_NOT_SPECIFIED; sd = &per_cpu(softnet_data, cpu); - rps_lock_irqsave(sd, &flags); + backlog_lock_irq_save(sd, &flags); if (!netif_running(skb->dev)) goto drop; qlen = skb_queue_len(&sd->input_pkt_queue); @ net/core/dev.c:4807 @ static int enqueue_to_backlog(struct sk_buff *skb, int cpu, enqueue: __skb_queue_tail(&sd->input_pkt_queue, skb); input_queue_tail_incr_save(sd, qtail); - rps_unlock_irq_restore(sd, &flags); + backlog_unlock_irq_restore(sd, &flags); return NET_RX_SUCCESS; } @ net/core/dev.c:4822 @ static int enqueue_to_backlog(struct sk_buff *skb, int cpu, drop: sd->dropped++; - rps_unlock_irq_restore(sd, &flags); + backlog_unlock_irq_restore(sd, &flags); dev_core_stats_rx_dropped_inc(skb->dev); kfree_skb_reason(skb, reason); @ net/core/dev.c:5888 @ static void flush_backlog(struct work_struct *work) local_bh_disable(); sd = this_cpu_ptr(&softnet_data); - rps_lock_irq_disable(sd); + backlog_lock_irq_disable(sd); skb_queue_walk_safe(&sd->input_pkt_queue, skb, tmp) { if (skb->dev->reg_state == NETREG_UNREGISTERING) { __skb_unlink(skb, &sd->input_pkt_queue); @ net/core/dev.c:5896 @ static void flush_backlog(struct work_struct *work) input_queue_head_incr(sd); } } - rps_unlock_irq_enable(sd); + backlog_unlock_irq_enable(sd); skb_queue_walk_safe(&sd->process_queue, skb, tmp) { if (skb->dev->reg_state == NETREG_UNREGISTERING) { @ net/core/dev.c:5914 @ static bool flush_required(int cpu) struct softnet_data *sd = &per_cpu(softnet_data, cpu); bool do_flush; - rps_lock_irq_disable(sd); + backlog_lock_irq_disable(sd); /* as insertion into process_queue happens with the rps lock held, * process_queue access may race only with dequeue */ do_flush = !skb_queue_empty(&sd->input_pkt_queue) || !skb_queue_empty_lockless(&sd->process_queue); - rps_unlock_irq_enable(sd); + backlog_unlock_irq_enable(sd); return do_flush; #endif @ net/core/dev.c:5987 @ static void net_rps_action_and_irq_enable(struct softnet_data *sd) #ifdef CONFIG_RPS struct softnet_data *remsd = sd->rps_ipi_list; - if (remsd) { + if (!use_backlog_threads() && remsd) { sd->rps_ipi_list = NULL; local_irq_enable(); @ net/core/dev.c:6002 @ static void net_rps_action_and_irq_enable(struct softnet_data *sd) static bool sd_has_rps_ipi_waiting(struct softnet_data *sd) { #ifdef CONFIG_RPS - return sd->rps_ipi_list != NULL; + return !use_backlog_threads() && sd->rps_ipi_list; #else return false; #endif @ net/core/dev.c:6036 @ static int process_backlog(struct napi_struct *napi, int quota) } - rps_lock_irq_disable(sd); + backlog_lock_irq_disable(sd); if (skb_queue_empty(&sd->input_pkt_queue)) { /* * Inline a custom version of __napi_complete(). @ net/core/dev.c:6046 @ static int process_backlog(struct napi_struct *napi, int quota) * We can use a plain write instead of clear_bit(), * and we dont need an smp_mb() memory barrier. */ - napi->state = 0; + napi->state &= NAPIF_STATE_THREADED; again = false; } else { skb_queue_splice_tail_init(&sd->input_pkt_queue, &sd->process_queue); } - rps_unlock_irq_enable(sd); + backlog_unlock_irq_enable(sd); } return work; @ net/core/dev.c:6760 @ static int napi_poll(struct napi_struct *n, struct list_head *repoll) static int napi_thread_wait(struct napi_struct *napi) { - bool woken = false; - set_current_state(TASK_INTERRUPTIBLE); while (!kthread_should_stop()) { @ net/core/dev.c:6768 @ static int napi_thread_wait(struct napi_struct *napi) * Testing SCHED bit is not enough because SCHED bit might be * set by some other busy poll thread or by napi_disable(). */ - if (test_bit(NAPI_STATE_SCHED_THREADED, &napi->state) || woken) { + if (test_bit(NAPI_STATE_SCHED_THREADED, &napi->state)) { WARN_ON(!list_empty(&napi->poll_list)); __set_current_state(TASK_RUNNING); return 0; } schedule(); - /* woken being true indicates this thread owns this napi. */ - woken = true; set_current_state(TASK_INTERRUPTIBLE); } __set_current_state(TASK_RUNNING); @ net/core/dev.c:6782 @ static int napi_thread_wait(struct napi_struct *napi) return -1; } +static void napi_threaded_poll_loop(struct napi_struct *napi) +{ + struct softnet_data *sd; + unsigned long last_qs = jiffies; + + for (;;) { + bool repoll = false; + void *have; + + local_bh_disable(); + sd = this_cpu_ptr(&softnet_data); + sd->in_napi_threaded_poll = true; + + have = netpoll_poll_lock(napi); + __napi_poll(napi, &repoll); + netpoll_poll_unlock(have); + + sd->in_napi_threaded_poll = false; + barrier(); + + if (sd_has_rps_ipi_waiting(sd)) { + local_irq_disable(); + net_rps_action_and_irq_enable(sd); + } + skb_defer_free_flush(sd); + local_bh_enable(); + + if (!repoll) + break; + + rcu_softirq_qs_periodic(last_qs); + cond_resched(); + } +} + static int napi_threaded_poll(void *data) { struct napi_struct *napi = data; - struct softnet_data *sd; - void *have; - while (!napi_thread_wait(napi)) { - unsigned long last_qs = jiffies; + while (!napi_thread_wait(napi)) + napi_threaded_poll_loop(napi); - for (;;) { - bool repoll = false; - - local_bh_disable(); - sd = this_cpu_ptr(&softnet_data); - sd->in_napi_threaded_poll = true; - - have = netpoll_poll_lock(napi); - __napi_poll(napi, &repoll); - netpoll_poll_unlock(have); - - sd->in_napi_threaded_poll = false; - barrier(); - - if (sd_has_rps_ipi_waiting(sd)) { - local_irq_disable(); - net_rps_action_and_irq_enable(sd); - } - skb_defer_free_flush(sd); - local_bh_enable(); - - if (!repoll) - break; - - rcu_softirq_qs_periodic(last_qs); - cond_resched(); - } - } return 0; } @ net/core/dev.c:11424 @ static int dev_cpu_dead(unsigned int oldcpu) list_del_init(&napi->poll_list); if (napi->poll == process_backlog) - napi->state = 0; + napi->state &= NAPIF_STATE_THREADED; else ____napi_schedule(sd, napi); } @ net/core/dev.c:11432 @ static int dev_cpu_dead(unsigned int oldcpu) raise_softirq_irqoff(NET_TX_SOFTIRQ); local_irq_enable(); + if (!use_backlog_threads()) { #ifdef CONFIG_RPS - remsd = oldsd->rps_ipi_list; - oldsd->rps_ipi_list = NULL; + remsd = oldsd->rps_ipi_list; + oldsd->rps_ipi_list = NULL; #endif - /* send out pending IPI's on offline CPU */ - net_rps_send_ipi(remsd); + /* send out pending IPI's on offline CPU */ + net_rps_send_ipi(remsd); + } /* Process offline CPU's input_pkt_queue */ while ((skb = __skb_dequeue(&oldsd->process_queue))) { @ net/core/dev.c:11778 @ static int net_page_pool_create(int cpuid) return 0; } +static int backlog_napi_should_run(unsigned int cpu) +{ + struct softnet_data *sd = per_cpu_ptr(&softnet_data, cpu); + struct napi_struct *napi = &sd->backlog; + + return test_bit(NAPI_STATE_SCHED_THREADED, &napi->state); +} + +static void run_backlog_napi(unsigned int cpu) +{ + struct softnet_data *sd = per_cpu_ptr(&softnet_data, cpu); + + napi_threaded_poll_loop(&sd->backlog); +} + +static void backlog_napi_setup(unsigned int cpu) +{ + struct softnet_data *sd = per_cpu_ptr(&softnet_data, cpu); + struct napi_struct *napi = &sd->backlog; + + napi->thread = this_cpu_read(backlog_napi); + set_bit(NAPI_STATE_THREADED, &napi->state); +} + +static struct smp_hotplug_thread backlog_threads = { + .store = &backlog_napi, + .thread_should_run = backlog_napi_should_run, + .thread_fn = run_backlog_napi, + .thread_comm = "backlog_napi/%u", + .setup = backlog_napi_setup, +}; + /* * This is called single threaded during boot, so no need * to take the rtnl semaphore. @ net/core/dev.c:11861 @ static int __init net_dev_init(void) init_gro_hash(&sd->backlog); sd->backlog.poll = process_backlog; sd->backlog.weight = weight_p; + INIT_LIST_HEAD(&sd->backlog.poll_list); if (net_page_pool_create(i)) goto out; } + if (use_backlog_threads()) + smpboot_register_percpu_thread(&backlog_threads); dev_boot_phase = 0; @ net/core/skbuff.c:7042 @ nodefer: __kfree_skb(skb); /* Make sure to trigger NET_RX_SOFTIRQ on the remote CPU * if we are unlucky enough (this seems very unlikely). */ - if (unlikely(kick) && !cmpxchg(&sd->defer_ipi_scheduled, 0, 1)) - smp_call_function_single_async(cpu, &sd->defer_csd); + if (unlikely(kick)) + kick_defer_list_purge(sd, cpu); } static void skb_splice_csum_page(struct sk_buff *skb, struct page *page,