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

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Date:	Mon, 28 Nov 2011 11:11:00 +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

On Sat, 2011-11-26 at 02:47 +0100, Stephane Eranian wrote:
> Here is a fixed version of Peter's patch.
> I fixed the compilation errors + added the missing
> linked list + spinlock initializations.
> 
> I also added the mmap_mutex in perf_poll() to avoid the
> race with perf_set_output(). It's not pretty but it solves
> the problem of a process getting stuck on a sampling buffer
> which is never going to get any samples. This was an unlikely
> scenario but we should take care of it anyway.
> 
> This patch solves the issue with loss of buffer notifications
> when sampling on multiple events at the same time. In that
> case fewer than expected samples would be captured.

Hehe, so it actually works eh.. amazing stuff ;-)

OK, I'll stick it in perf/urgent.. Thanks Stephane!

If anybody happens upon a prettier solution, don't be shy and please do
tell us ;-)


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