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.
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
kernel/events/core.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index afbf388a5176..5baf7f981f23 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -11622,6 +11622,9 @@ 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);
--
2.35.1.1021.g381101b075-goog
