[PATCH 5.16 247/285] perf/core: Inherit event_caps

Greg Kroah-Hartman
2022-04-12T08:11:09Z

From: Namhyung Kim <namhyung@kernel.org>

commit e3265a4386428d3d157d9565bb520aabff8b4bf0 upstream.

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: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20220328200112.457740-1-namhyung@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/events/core.c | 3 +++
1 file changed, 3 insertions(+)

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -11626,6 +11626,9 @@ perf_event_alloc(struct perf_event_attr

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);