From 857c5229514affff639badafb10269b9e2e08fad Mon Sep 17 00:00:00 2001 From: Thomas Gleixner <tglx@linutronix.de> Date: Fri, 24 Sep 2021 18:12:45 +0200 Subject: [PATCH 031/158] x86/softirq: Disable softirq stacks on PREEMPT_RT PREEMPT_RT preempts softirqs and the current implementation avoids do_softirq_own_stack() and only uses __do_softirq(). Disable the unused softirqs stacks on PREEMPT_RT to safe some memory and ensure that do_softirq_own_stack() is not used which is not expected. [bigeasy: commit description.] Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Link: https://lore.kernel.org/r/20210924161245.2357247-1-bigeasy@linutronix.de --- arch/x86/include/asm/irq_stack.h | 3 +++ arch/x86/kernel/irq_32.c | 2 ++ 2 files changed, 5 insertions(+) Index: linux-5.15.19-rt29/arch/x86/include/asm/irq_stack.h =================================================================== @ linux-5.15.19-rt29/arch/x86/include/asm/irq_stack.h:204 @ IRQ_CONSTRAINTS, regs, vector); \ } +#ifndef CONFIG_PREEMPT_RT /* * Macro to invoke __do_softirq on the irq stack. This is only called from * task context when bottom halves are about to be reenabled and soft @ linux-5.15.19-rt29/arch/x86/include/asm/irq_stack.h:218 @ __this_cpu_write(hardirq_stack_inuse, false); \ } +#endif + #else /* CONFIG_X86_64 */ /* System vector handlers always run on the stack they interrupted. */ #define run_sysvec_on_irqstack_cond(func, regs) \ Index: linux-5.15.19-rt29/arch/x86/kernel/irq_32.c =================================================================== --- linux-5.15.19-rt29.orig/arch/x86/kernel/irq_32.c +++ linux-5.15.19-rt29/arch/x86/kernel/irq_32.c @ linux-5.15.19-rt29/arch/x86/include/asm/irq_stack.h:135 @ int irq_init_percpu_irqstack(unsigned in return 0; } +#ifndef CONFIG_PREEMPT_RT void do_softirq_own_stack(void) { struct irq_stack *irqstk; @ linux-5.15.19-rt29/arch/x86/include/asm/irq_stack.h:152 @ void do_softirq_own_stack(void) call_on_stack(__do_softirq, isp); } +#endif void __handle_irq(struct irq_desc *desc, struct pt_regs *regs) {