linux-kernel - Re: [PATCH] perf/stat: fix bug in handling events in error state

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Date:   Thu, 13 Apr 2017 10:28:15 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     David Carrillo-Cisneros <davidcc@...gle.com>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Wang Nan <wangnan0@...wei.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Stephane Eranian <eranian@...gle.com>,
        Paul Turner <pjt@...gle.com>
Subject: Re: [PATCH] perf/stat: fix bug in handling events in error state

On Wed, Apr 12, 2017 at 11:23:01AM -0700, David Carrillo-Cisneros wrote:
> From: Stephane Eranian <eranian@...gle.com>
> 
> (This is a patch has been sitting in the Intel CQM/CMT driver series
>  for a while, despite not depend on it. Sending it now independently
>  since the series is being discarded.)
> 
> When an event is in error state, read() returns 0
> instead of sizeof() buffer. In certain modes, such
> as interval printing, ignoring the 0 return value
> may cause bogus count deltas to be computed and
> thus invalid results printed.
> 
> This patch fixes this problem by modifying read_counters()
> to mark the event as not scaled (scaled = -1) to force
> the printout routine to show <NOT COUNTED>.
> 
> Signed-off-by: Stephane Eranian <eranian@...gle.com>
> Reviewed-by: David Carrillo-Cisneros <davidcc@...gle.com>

Acked-by: Jiri Olsa <jolsa@...nel.org>

thanks,
jirka