Re: [PATCH 1/2] cgroup: Use irqsave in cgroup_rstat_flush_locked().

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Hello,

On Tue, Mar 01, 2022 at 01:21:42PM +0100, Sebastian Andrzej Siewior wrote:
> 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@xxxxxxxxxxxxx>

Can you please add a comment explaining why irqsave is being used? As it
stands, it just looks spurious.

Thanks.

-- 
tejun



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