linux-kernel - Re: [RFC v2] perf: Rewrite core context handling

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Date:   Mon, 29 Aug 2022 13:58:29 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ravi Bangoria <ravi.bangoria@....com>
Cc:     acme@...nel.org, alexander.shishkin@...ux.intel.com,
        jolsa@...hat.com, namhyung@...nel.org, songliubraving@...com,
        eranian@...gle.com, alexey.budankov@...ux.intel.com,
        ak@...ux.intel.com, mark.rutland@....com, megha.dey@...el.com,
        frederic@...nel.org, maddy@...ux.ibm.com, irogers@...gle.com,
        kim.phillips@....com, linux-kernel@...r.kernel.org,
        santosh.shukla@....com
Subject: Re: [RFC v2] perf: Rewrite core context handling

On Mon, Aug 29, 2022 at 09:30:50AM +0530, Ravi Bangoria wrote:
> > With this, I can run 'perf test' and perf_event_tests without any error in
> > dmesg. I'll run perf fuzzer over night and see if it reports any issue.
> 
> I also ran fuzzer on Intel machine over the weekend. I see only one WARN_ON()
> hit. Otherwise system is running normal. FWIW, I was running fuzzer as normal
> user with perf_event_paranoid=0.
> 
>   WARNING: CPU: 3 PID: 2840537 at arch/x86/events/core.c:1606 x86_pmu_stop+0xd0/0x100

That's the WARN about PERF_HES_STOPPED already being set.

>   Call Trace:
>    <TASK>
>    x86_pmu_del+0x8e/0x2d0
>    ? debug_smp_processor_id+0x17/0x20
>    event_sched_out+0x10b/0x2b0
>    ? x86_pmu_del+0x5c/0x2d0
>    merge_sched_in+0x39f/0x410

And this callchain suggests this is the group_error path.

I can't immediately spot a fail there, but I'll try and stare at it
some.