Commit e3265a43 authored by Namhyung Kim's avatar Namhyung Kim Committed by Peter Zijlstra
Browse files

perf/core: Inherit event_caps 



It was reported that some perf event setup can make fork failed on
ARM64.  It was the case of a group of mixed hw and sw events and it
failed in perf_event_init_task() due to armpmu_event_init().

The ARM PMU code checks if all the events in a group belong to the
same PMU except for software events.  But it didn't set the event_caps
of inherited events and no longer identify them as software events.
Therefore the test failed in a child process.

A simple reproducer is:

  $ perf stat -e '{cycles,cs,instructions}' perf bench sched messaging
  # Running 'sched/messaging' benchmark:
  perf: fork(): Invalid argument

The perf stat was fine but the perf bench failed in fork().  Let's
inherit the event caps from the parent.

Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20220328200112.457740-1-namhyung@kernel.org
parent ad4878d4

kernel/events/core.c

+3 −0
Original line number Diff line number Diff line
@@ -11635,6 +11635,9 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu, 


	event->state		= PERF_EVENT_STATE_INACTIVE;



	if (parent_event)

		event->event_caps = parent_event->event_caps;



	if (event->attr.sigtrap)

		atomic_set(&event->event_limit, 1);