linux-kernel - Re: [PATCH 03/11] perf: Do not get values from disabled counters in group format read

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Date:	Thu, 2 May 2013 15:39:29 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	linux-kernel@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>, Paul Mackerras <paulus@...ba.org>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Namhyung Kim <namhyung@...nel.org>
Subject: Re: [PATCH 03/11] perf: Do not get values from disabled counters
 in group format read

On Mon, Feb 04, 2013 at 01:32:57PM +0100, Jiri Olsa wrote:
> From: "jolsa@...hat.com" <jolsa@...hat.com>
> 
> It's possible some of the counters in the group could be
> disabled when sampling member of the event group is reading
> the rest via PERF_SAMPLE_READ sample type processing. Disabled
> counters could then produce wrong numbers.
> 
> Fixing that by reading only enabled counters for PERF_SAMPLE_READ
> sample type processing.
> 
> Signed-off-by: Jiri Olsa <jolsa@...hat.com>
> Cc: Arnaldo Carvalho de Melo <acme@...stprotocols.net>

I had to like re-read our previous thread on this; which I think says that the
Changelog isn't perfect. However:

Acked-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>

> Cc: Ingo Molnar <mingo@...e.hu>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Corey Ashford <cjashfor@...ux.vnet.ibm.com>
> Cc: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> ---
>  kernel/events/core.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 4081261..e2ea1b9 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -4018,7 +4018,8 @@ static void perf_output_read_group(struct perf_output_handle *handle,
>  	list_for_each_entry(sub, &leader->sibling_list, group_entry) {
>  		n = 0;
>  
> -		if (sub != event)
> +		if ((sub != event) &&
> +		    (sub->state == PERF_EVENT_STATE_ACTIVE))
>  			sub->pmu->read(sub);
>  
>  		values[n++] = perf_event_count(sub);
> -- 
> 1.7.11.7
> 
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