perf/ring_buffer: Trigger IO signals for watermark_wakeup

perf_output_wakeup() already marks the perf event fd available for polling.
Trigger IO signals with FASYNC too.
Signed-off-by: Kyle Huey <khuey@kylehuey.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20240413141618.4160-3-khuey@kylehuey.com

kernel/events/ring_buffer.c

@@ -22,6 +22,10 @@ static void perf_output_wakeup(struct perf_output_handle *handle)
 	atomic_set(&handle->rb->poll, EPOLLIN);
 
 	handle->event->pending_wakeup = 1;
+
+	if (*perf_event_fasync(handle->event) && !handle->event->pending_kill)
+		handle->event->pending_kill = POLL_IN;
+
 	irq_work_queue(&handle->event->pending_irq);
 }