perf: Ensure swevent hrtimer is properly destroyed

With the change to hrtimer_try_to_cancel() in
perf_swevent_cancel_hrtimer() it appears possible for the hrtimer to
still be active by the time the event gets freed.

Make sure the event does a full hrtimer_cancel() on the free path by
installing a perf_event::destroy handler.

Fixes: eb3182ef0405 ("perf/core: Fix system hang caused by cpu-clock usage")
Reported-by: CyberUnicorns <a101e_iotvul@163.com>
Tested-by: CyberUnicorns <a101e_iotvul@163.com>
Debugged-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

diff --git a/kernel/events/core.c b/kernel/events/core.c
index dad0d3d2e85f7d1446b2988c34e31771f6faded0..e3d8338fd51c1de4cbc99dd051c6ab7a9e19df14 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -11906,6 +11906,11 @@ static void perf_swevent_cancel_hrtimer(struct perf_event *event)
        }
 }
 
+static void perf_swevent_destroy_hrtimer(struct perf_event *event)
+{
+       hrtimer_cancel(&event->hw.hrtimer);
+}
+
 static void perf_swevent_init_hrtimer(struct perf_event *event)
 {
        struct hw_perf_event *hwc = &event->hw;
@@ -11914,6 +11919,7 @@ static void perf_swevent_init_hrtimer(struct perf_event *event)
                return;
 
        hrtimer_setup(&hwc->hrtimer, perf_swevent_hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
+       event->destroy = perf_swevent_destroy_hrtimer;
 
        /*
         * Since hrtimers have a fixed rate, we can do a static freq->period