From: Peter Zijlstra <peterz@infradead.org>
To: Vince Weaver <vincent.weaver@maine.edu>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Stephane Eranian <eranian@google.com>
Subject: Re: perf: FORMAT_GROUP on attached process stops working in 3.16-rc
Date: Tue, 15 Jul 2014 16:37:45 +0200 [thread overview]
Message-ID: <20140715143745.GK9918@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <alpine.DEB.2.11.1407151030550.20353@vincent-weaver-1.umelst.maine.edu>
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On Tue, Jul 15, 2014 at 10:36:33AM -0400, Vince Weaver wrote:
> Hello
>
> I noticed in the 3.16-rc kernels that one of my regression tests was
> failing, specifically
> https://github.com/deater/perf_event_tests/blob/master/tests/bugs/read_group_attached.c
>
> This test creates an event group with two events and PERF_FORMAT_GROUP
> set.
>
> It creates a child process, stops it, attaches the event group to it,
> starts the events and the child, waits for the child to finish, stops the
> events, then reads the value.
>
> In theory a subsequent read from the group leader should return values for
> *both* events (due to PERF_FORMAT_GROUP) but this stopped working, it only
> returns the value for the leader.
>
> I've bisected it down to change: 15a2d4de0eab5
> "perf: Always destroy groups on exit"
>
> So is this expected behavior due to this patch, or is it a regression?
Regression, lemme try and wrap my head around it. Thanks!
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next prev parent reply other threads:[~2014-07-15 14:38 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-15 14:36 Vince Weaver
2014-07-15 14:37 ` Peter Zijlstra [this message]
2014-07-15 15:35 ` Peter Zijlstra
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