From c350705d725b07cd92ee77500fdb5b10cd4990a0 Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Tue, 3 Jul 2018 18:19:48 +0200 Subject: [PATCH 073/166] cgroup: use irqsave in cgroup_rstat_flush_locked() All callers of cgroup_rstat_flush_locked() acquire cgroup_rstat_lock either with spin_lock_irq() or spin_lock_irqsave(). cgroup_rstat_flush_locked() itself acquires cgroup_rstat_cpu_lock which is a raw_spin_lock. This lock is also acquired in cgroup_rstat_updated() in IRQ context and therefore requires _irqsave() locking suffix in cgroup_rstat_flush_locked(). Since there is no difference between spin_lock_t and raw_spin_lock_t on !RT lockdep does not complain here. On RT lockdep complains because the interrupts were not disabled here and a deadlock is possible. Acquire the raw_spin_lock_t with disabled interrupts. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Link: https://www.spinics.net/lists/cgroups/msg23051.html --- kernel/cgroup/rstat.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) Index: linux-5.15.32-rt39/kernel/cgroup/rstat.c =================================================================== --- linux-5.15.32-rt39.orig/kernel/cgroup/rstat.c +++ linux-5.15.32-rt39/kernel/cgroup/rstat.c @@ -156,8 +156,9 @@ static void cgroup_rstat_flush_locked(st raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu); struct cgroup *pos = NULL; + unsigned long flags; - raw_spin_lock(cpu_lock); + raw_spin_lock_irqsave(cpu_lock, flags); while ((pos = cgroup_rstat_cpu_pop_updated(pos, cgrp, cpu))) { struct cgroup_subsys_state *css; @@ -169,7 +170,7 @@ static void cgroup_rstat_flush_locked(st css->ss->css_rstat_flush(css, cpu); rcu_read_unlock(); } - raw_spin_unlock(cpu_lock); + raw_spin_unlock_irqrestore(cpu_lock, flags); /* if @may_sleep, play nice and yield if necessary */ if (may_sleep && (need_resched() ||