linux-kernel - Re: [PATCH 6/8] perf: Account freq events per cpu

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Message-ID: <20130801133549.GC27162@twins.programming.kicks-ass.net>
Date:	Thu, 1 Aug 2013 15:35:49 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 6/8] perf: Account freq events per cpu

On Thu, Aug 01, 2013 at 03:31:55PM +0200, Peter Zijlstra wrote:
> the branch_stack thing tests ATTACH_TASK, which should also be good, but
> leaves me wonder wth they do for those that are attached to tasks.

Ah found it, in intel_pmu_lbr_enable() we test cpuc->lbr_context against
event->ctx and wipe the LBR if they differ, that should indeed avoid the
leak but isn't sufficient to guarantee sane data as the context swap for
inherited counters can foil this.


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