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Date: Thu, 13 Apr 2017 10:28:15 +0200
From: Jiri Olsa <jolsa@redhat.com>
To: David Carrillo-Cisneros <davidcc@google.com>
Cc: linux-kernel@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Wang Nan <wangnan0@huawei.com>, Andi Kleen <ak@linux.intel.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Mathieu Poirier <mathieu.poirier@linaro.org>,
        Stephane Eranian <eranian@google.com>, Paul Turner <pjt@google.com>
Subject: Re: [PATCH] perf/stat: fix bug in handling events in error state
Message-ID: <20170413082815.GC4784@krava>
References: <20170412182301.44406-1-davidcc@google.com>
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On Wed, Apr 12, 2017 at 11:23:01AM -0700, David Carrillo-Cisneros wrote:
> From: Stephane Eranian <eranian@google.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@google.com>
> Reviewed-by: David Carrillo-Cisneros <davidcc@google.com>

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

thanks,
jirka