linux-kernel - Re: [PATCH] perf_event: fix loss of notification with multi-event sampling

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Date:	Wed, 23 Nov 2011 11:36:46 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu
Subject: Re: [PATCH] perf_event: fix loss of notification with multi-event
 sampling

On Wed, 2011-11-23 at 11:10 +0100, Stephane Eranian wrote:
> On Wed, Nov 23, 2011 at 11:06 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> > On Wed, 2011-11-23 at 10:30 +0100, Stephane Eranian wrote:
> >>
> >> In the case of perf_event, we are not in a producer-consumer model, so
> >> it seems like the behavior we have now is correct. The caller of poll()
> >> gets stuck if the file descriptor is closed.
> >
> > But wouldn't out event->waitq still be referenced by that waiting task?
> > Even though we freed it in our fops->release() callback?
> >
> I suspect you don't end up in fops->release() if you have an ongoing poll
> because you've probably increment the file's refcount along the way.

You're quite right, poll does that internally. Ok, so we don't need to
worry about this bit then.
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