s390/pai: Handle multiple PMU stop callback invocations

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Handle the following scenario:
The kernel protects itself against a very high sampling load and
throttles the sampling using:

  perf_event_throttle() --> PMU->stop()

Shortly later the scheduler may terminate the task and removes it from the
CPU. It again calls

  PMU->stop()

which results in two invocations of PMU->stop() called back to back.
Protect against this and check the PERF_HES_STOPPED bit on function
entry.  If it is already set return.
Clear bit PERF_HES_STOPPED in PMU->start().

Prohibit ioctl(fd, PERF_EVENT_IOC_PERIOD, ...) call for this event.
It sets perf_event::event_limit to a positive value and causes
perf_event_overflow() to invoke pai_stop() call back function when
perf_event::event_limit hits zero. This is not supported because the
sample events CRYPTO_ALL and NNPA_ALL are only taken at schedule out
of a task.

Use list_for_each_entry_safe() for safe iteration over syswide_list
in pai_have_samples().

Fixes: 9f66572f28 ("s390/pai_crypto: Enable per-task and system-wide sampling event")
Fixes: 582cc1b28e ("s390/pai_ext: Enable per-task and system-wide sampling event")
Cc: stable@vger.kernel.org # v6.19+
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Reviewed-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

...

This commit is contained in:

Thomas Richter 2026-08-19 07:58:55 +02:00 • committed by Heiko Carstens

parent 439077c39d

commit f3110e969a

1 changed files with 23 additions and 2 deletions

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arch/s390/kernel/perf_pai.c

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