linux-kernel - Re: [BUG] perf_event: when events are grouped, the time enabled / running values are incorrect

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Date:	Fri, 07 May 2010 19:24:49 -0700
From:	Corey Ashford <cjashfor@...ux.vnet.ibm.com>
To:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Paul Mackerras <paulus@...ba.org>
CC:	Stephane Eranian <eranian@...glemail.com>
Subject: Re: [BUG] perf_event: when events are grouped, the time enabled /
 running values are incorrect

On 05/07/2010 06:56 PM, Corey Ashford wrote:
> Hi,
>
> There appears to be a bug in the kernel related to reading up the time
> running and enabled values for events that are in a group. The group
> leader's time running and time enable values look correct, but all of
> the other group members have a zero value for their time running and
> time enabled fields.
>
> This happens only when remote monitoring a process (perhaps only after
> it has terminated)... when self monitoring, the time running/enabled
> values come out non-zero, and the values are the same for all of the
> counters (as one would expect since they can be enabled/disabled
> simultaneously).
>
> I've attached a test case which you can place in the tools/perf
> subdirectory and compile with just:
>
> gcc -o show_re_bug show_re_bug.c

I forgot to mention that you should run this with some sort of the load 
program, like

./show_re_bug md5sum `which gdb`

- Corey
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