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

* Stephane Eranian <eranian@google.com> 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.

Please send a patch against tip:master (or perf/urgent), on top
of:

84f2b9b2edc0: perf: Remove deprecated WARN_ON_ONCE()

Note that I updated that patch to removed one more WARN_ON()
than you originally sent - please add it back as appropriate, in
the delta fix patch.

Thanks,

Ingo


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