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. 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.

Cc: Will Deacon will@kernel.org Cc: Mark Rutland mark.rutland@arm.com Cc: stable@vger.kernel.org Signed-off-by: Namhyung Kim namhyung@kernel.org --- kernel/events/core.c | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/kernel/events/core.c b/kernel/events/core.c index fc18664f49b0..e28f63ae625b 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -11560,6 +11560,9 @@ 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);