On Tue, May 14, 2013 at 05:28:36PM +0200, Oleg Nesterov wrote:
> On 05/14, Tejun Heo wrote:
> >
> > > +int percpu_ref_tryget(struct percpu_ref *ref)
> > > +{
> > > + int ret = 1;
> > > +
> > > + preempt_disable();
> > > +
> > > + if (!percpu_ref_dead(ref))
> > > + percpu_ref_get(ref);
> > > + else
> > > + ret = 0;
> > > +
> > > + preempt_enable();
> > > +
> > > + return ret;
> > > +}
> ...
> > BTW, why is this
> > function necessary? What's the use case?
>
> Yes, I was wondering too.
>
> And please note that this code _looks_ wrong, percpu_ref_get() still
> can increment ref->count.
Yeah I see what you mean, I changed how ret is set.
But also splitting tryget() and count() out into another patch to go
with the module conversion.
> Hmm. Just noticed this comment above percpu_ref_kill()
>
> * The caller must issue a synchronize_rcu()/call_rcu() before calling
> * percpu_ref_put() to drop the initial ref.
>
> Really?
That's also left over from the dynamic version, whoops.
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