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SubjectRe: Perf: BUG: kernel NULL pointer dereference, address: 0000000000000198
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On 03-Nov-22 9:42 PM, Ravi Bangoria wrote:
> 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.

git bisect let me to a BRS patch:

commit ada543459cab7f653dcacdaba4011a8bb19c627c
Author: Stephane Eranian <eranian@google.com>
Date: Tue Mar 22 15:15:07 2022 -0700

perf/x86/amd: Add AMD Fam19h Branch Sampling support

Add support for the AMD Fam19h 16-deep branch sampling feature as
described in the AMD PPR Fam19h Model 01h Revision B1. This is a model
specific extension. It is not an architected AMD feature.

Thanks,
Ravi

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