From: Ravi Bangoria <ravi.bangoria@amd.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Naresh Kamboju <naresh.kamboju@linaro.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Borislav Petkov <bp@alien8.de>, Ingo Molnar <mingo@redhat.com>,
linux-perf-users@vger.kernel.org,
open list <linux-kernel@vger.kernel.org>,
regressions@lists.linux.dev, lkft-triage@lists.linaro.org,
Stephane Eranian <eranian@google.com>,
Sandipan Das <sandipan.das@amd.com>,
Ravi Bangoria <ravi.bangoria@amd.com>
Subject: Re: Perf: BUG: kernel NULL pointer dereference, address: 0000000000000198
Date: Thu, 3 Nov 2022 21:42:56 +0530 [thread overview]
Message-ID: <f00ecc51-a387-1801-0db6-e18060c620a7@amd.com> (raw)
In-Reply-To: <Y2O1GDRrJqIu17vM@hirez.programming.kicks-ass.net>
On 03-Nov-22 6:03 PM, Peter Zijlstra wrote:
> On Thu, Nov 03, 2022 at 05:15:30PM +0530, Ravi Bangoria wrote:
>
>> Sorry was distracted a bit. So, this seems to be happening because of
>> race between amd_pmu_enable_all() and perf event NMI. Something like:
>>
>> amd_pmu_enable_all()
>> {
>> if (!test_bit(idx, cpuc->active_mask))
>>
>> --->/* perf NMI entry */
>> ...
>> x86_pmu_stop() {
>> __clear_bit(hwc->idx, cpuc->active_mask);
>> cpuc->events[hwc->idx] = NULL;
>> }
>> ...
>> <---/* perf NMI exit */
>>
>> amd_pmu_enable_event(cpuc->events[idx]);
>> }
>
> Hmm, do you have more information?
I've extracted function graph logs from crash dump and uploaded it here:
https://github.com/BangoriaRavi/function_graph/blob/main/trace.function_graph.dat
crash was on CPU1.
> Something like that would require
> calling amd_pmu_enable_all() while it is already active -- and that
> seems suspect at first glance.
>
> That is, you shouldn't be getting an NMI for @idx before
> amd_pmu_enable_event().
I too was wondering about this. Will try to get some more data tomorrow.
Thanks,
Ravi
next prev parent reply other threads:[~2022-11-03 16:13 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-20 6:54 Naresh Kamboju
2022-10-25 4:29 ` Ravi Bangoria
2022-10-25 13:06 ` Ravi Bangoria
2022-10-26 10:05 ` Ravi Bangoria
2022-11-03 11:45 ` Ravi Bangoria
2022-11-03 12:33 ` Peter Zijlstra
2022-11-03 16:12 ` Ravi Bangoria [this message]
2022-11-07 10:29 ` Ravi Bangoria
2022-11-14 4:40 ` [PATCH] perf/x86/amd: Fix crash due to race between amd_pmu_enable_all, perf NMI and throttling Ravi Bangoria
2022-11-16 9:21 ` [tip: perf/urgent] " tip-bot2 for Ravi Bangoria
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