Re: WARNING: at arch/x86/kernel/cpu/perf_event.c:989

From: Peter Zijlstra
Date: Mon Feb 06 2012 - 09:29:34 EST


On Mon, 2012-02-06 at 15:13 +0100, Stephane Eranian wrote:
> Ok, I found the problem!
>
> it comes from perf_adjust_freq_unthr_context() vs perf_adjust_period().
> The latter can under certain condition stop and restart the event. So we
> had:
>
> stop()
> if (delta > 0) {
> perf_adjust_period() {
> if (period > 8*...) {
> stop()
> ...
> start()
> }
> }
> }
> start()
>
> Could have a double stop() and double start(), thus triggering the warning in
> x86_pmu_start().
>
> Will post a patch shortly to fix this.

Nice, thanks for looking at this!

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