Re: [PATCH v4] s390/pai: Handle multiple PMU stop callback invocations

[Thomas Richter <tmricht@linux.ibm.com>]

On 8/19/26 08:11, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
> 
> Pre-existing issues:
> - [Medium] `list_for_each_entry_safe` in `pai_have_samples()` is insufficient to prevent list corruption (dereferencing `LIST_POISON1`) when group throttling removes sibling events concurrently.

perf_event_throttle_group() walks a different list anchored
by perf_event::sibling_list. The list anchored by cpuhw::syswide
is a complete different list using different nodes.
Since events CRYPTO_ALL and NNPA_ALL are single sampling events
and the only sampling event for each PAI PMU, it makes no sense
to group the same event. Events of different PMUS can not be grouped
anyway.

> - [Medium] The patch fails to prohibit setting `event_limit`, leaving the unsupported `pai_stop()` invocation pathway open via `PERF_EVENT_IOC_REFRESH`.
> --
> 
This needs to be addressed in a follow-on patch, the invocation of perf_event_refresh() can not
be blocked right now. Maybe add a new PMU call back.


-- 
Thomas Richter, Dept 3303, IBM s390 Linux Development, Boeblingen, Germany
--
IBM Deutschland Research & Development GmbH

Vorsitzender des Aufsichtsrats: Wolfgang Wendt

Geschäftsführung: David Faller

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