linux-kernel - Re: pmu::read() called erroneously in v4.13-rc{3,4}

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Message-ID: <20170821144614.GA15568@krava>
Date:   Mon, 21 Aug 2017 16:46:14 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Mark Rutland <mark.rutland@....com>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vince Weaver <vince@...ter.net>, Ingo Molnar <mingo@...nel.org>
Subject: Re: pmu::read() called erroneously in v4.13-rc{3,4}

On Fri, Aug 11, 2017 at 12:18:07PM +0100, Mark Rutland wrote:

SNIP

> 
> I'm also confused by perf_output_read_group() when event == leader.
> AFAICT, in that case we won't read() the event at all, and we'll only
> read() the siblings. Is that right?

I think we assume perf_output_read_group is only called from event's
PMI which means it's already been called for event

jirka