linux-kernel - Re: [BUG] perf: sharing of cpuctx between core and ibs PMU causes problems

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Date:	Thu, 09 Aug 2012 20:08:27 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	"Yan, Zheng" <zheng.z.yan@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Robert Richter <robert.richter@....com>, mingo@...e.hu
Subject: Re: [BUG] perf: sharing of cpuctx between core and ibs PMU causes
 problems

On Thu, 2012-08-09 at 16:05 +0200, Stephane Eranian wrote:
> > uncore PMU does not have this issue because uncore_pmu->task_ctx_nr
> > is 'perf_invalid_context'. find_pmu_context() always return NULL in
> > that case.
> >
> Yes, I think IBS should do the same and that should fix the problem
> there too. Will try that. 

I'm afraid not, per-task profiling with uncore doesn't really make that
much sense. For IBS it does.

We can't share a context with different PMUs, that'll totally mess up
the event scheduling.

We'll have to grow perf_event_task_context with an extra context and
have IBS use that.
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