Re: [PATCH V10 00/10] arm64/perf: Enable branch stack sampling

[James Clark]

On 29/05/2023 05:35, Anshuman Khandual wrote:
> 
> 
> On 5/17/23 07:54, Anshuman Khandual wrote:
>> This series enables perf branch stack sampling support on arm64 platform
>> via a new arch feature called Branch Record Buffer Extension (BRBE). All
>> relevant register definitions could be accessed here.
>>
>> https://developer.arm.com/documentation/ddi0601/2021-12/AArch64-Registers
>>
>> This series applies on 6.4-rc2.
>>
>> Changes in V10:
>>
>> - Rebased the series on v6.4-rc2
>> - Moved ARMV8 PMUV3 changes inside drivers/perf/arm_pmuv3.c
>> - Moved BRBE driver changes inside drivers/perf/arm_brbe.[c|h]
>> - Moved the WARN_ON() inside the if condition in armv8pmu_handle_irq()
> 
> Hello Will/Mark,
> 
> There was a crash reported on V9 (applicable here in V10 as well) because of
> accessing event->pmu_ctx->task_ctx_data during a PMU IRQ for per-cpu events,
> where it would not have been allocated in the first place. I have proposed a
> fix for that on the other thread [1]. Besides, does the series looks good in
> the current form ? Unless there are other comments, will respin with the fix
> later in the week. Thank you.
> 
> [1] https://lore.kernel.org/linux-arm-kernel/d02df808-6d2b-c24b-bc8d-8f4859c0c71b@xxxxxxx/
> 
> - Anshuman


Hi Anshuman,

With the new fix I don't get the crash anymore and the tests are all
passing so:

Tested-by: James Clark <james.clark@xxxxxxx>