# Re: \[PATCH\] powerpc/stacktrace: fix raise\_backtrace\_ipi() logic

- From: Nathan Lynch \<hidden\>
- Date: 2021-06-07 21:51:38 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2021/06/9523004
- Thread: https://ratatoskr.run/linuxppc-dev/2021/05/9522895/t.md

```text
Michael Ellerman [ref] writes:
> Nathan Lynch [ref] writes:
>> Hi Michael,
>>
>> Michael Ellerman [ref] writes:
>>> Nathan Lynch [ref] writes:
>>>> When smp_send_safe_nmi_ipi() indicates that the target CPU has
>>>> responded to the IPI, skip the remote paca inspection
>>>> fallback. Otherwise both the sending and target CPUs attempt the
>>>> backtrace, usually creating a misleading ("didn't respond to backtrace
>>>> IPI" is wrong) and interleaved mess:
>>>
>>> Thanks for fixing my bugs for me :)
>>>
>>
>> Thanks for your review! I was beginning to think I had missed some
>> subtletly here, thanks for illustrating it.
>>
>> I'll run with your proposed change below for the problem I'm working.
>
> Thanks. I did test it a bit with the test_lockup module, but some real
> world testing would be good too.

Been running with this to work some LPM issues and can confirm it waits
the intended amount of time before falling back to a remote stack walk,
avoiding interleaved traces from source and target CPUs. You can add my
tested-by, thanks.
```