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Date: Mon, 21 Aug 2017 16:46:14 +0200
From: Jiri Olsa <jolsa@redhat.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: linux-kernel@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
        Andi Kleen <ak@linux.intel.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Jiri Olsa <jolsa@kernel.org>, Stephane Eranian <eranian@google.com>,
        Thomas Gleixner <tglx@linutronix.de>, Vince Weaver <vince@deater.net>,
        Ingo Molnar <mingo@kernel.org>
Subject: Re: pmu::read() called erroneously in v4.13-rc{3,4}
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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