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SubjectRe: [PATCH 2/4] lib/percpu-refcount: introduce percpu_ref_resurge()
On Wed, Sep 19, 2018 at 01:19:10PM +0800, jianchao.wang wrote:
> Hi Ming
>
> On 09/18/2018 06:19 PM, Ming Lei wrote:
> > + unsigned long __percpu *percpu_count;
> > +
> > + WARN_ON_ONCE(__ref_is_percpu(ref, &percpu_count));
> > +
> > + /* get one extra ref for avoiding race with .release */
> > + rcu_read_lock_sched();
> > + atomic_long_add(1, &ref->count);
> > + rcu_read_unlock_sched();
> > + }
>
> The rcu_read_lock_sched here is redundant. We have been in the critical section
> of a spin_lock_irqsave.

Right.

>
> The atomic_long_add(1, &ref->count) may have two result.
> 1. ref->count > 1
> it will not drop to zero any more.
> 2. ref->count == 1
> it has dropped to zero and .release may be running.

IMO, both the two cases are fine and supported, or do you have other
concern about this way?

thanks,
Ming

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