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

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Date:	Wed, 23 Nov 2011 11:10:15 +0100
From:	Stephane Eranian <eranian@...gle.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu
Subject: Re: [PATCH] perf_event: fix loss of notification with multi-event sampling

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.
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