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Subject: Re: [BUG] perf_event: when events are grouped, the time enabled / 
 running values are incorrect
From: Peter Zijlstra <peterz@infradead.org>
To: eranian@gmail.com
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       LKML <linux-kernel@vger.kernel.org>, Paul Mackerras <paulus@samba.org>,
       eranian@google.com
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Date: Tue, 11 May 2010 22:11:16 +0200
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On Tue, 2010-05-11 at 21:55 +0200, stephane eranian wrote:
> Events are also grouped in this example. Both this same issue exists
> also when only
> one event is used. I suspect an update_event_times() or
> update_group_times() is also
> missing on the sampling path in perf_overflow_handler().

Hrmm, you're right, except fixing that is non-trivial.
update_event_times() wants to be called with ctx->lock held and we can't
do that from NMI context.