| From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> |
| Date: Tue, 3 Jul 2018 18:19:48 +0200 |
| Subject: [PATCH] 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 <bigeasy@linutronix.de> |
| --- |
| kernel/cgroup/rstat.c | 5 +++-- |
| 1 file changed, 3 insertions(+), 2 deletions(-) |
| |
| --- a/kernel/cgroup/rstat.c |
| +++ b/kernel/cgroup/rstat.c |
| @@ -160,8 +160,9 @@ 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; |
| |
| @@ -173,7 +174,7 @@ 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() || |