Patch "perf: Fix fasync handling on inherited events" has been added to the 3.14-stable tree

This is a note to let you know that I've just added the patch titled

perf: Fix fasync handling on inherited events

to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
perf-fix-fasync-handling-on-inherited-events.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Peter Zijlstra <[email protected]>
Date: Thu, 11 Jun 2015 10:32:01 +0200
Subject: perf: Fix fasync handling on inherited events

From: Peter Zijlstra <[email protected]>

commit fed66e2cdd4f127a43fd11b8d92a99bdd429528c upstream.

Vince reported that the fasync signal stuff doesn't work proper for inherited events. So fix that.

Installing fasync allocates memory and sets filp->f_flags |= FASYNC, which upon the demise of the file descriptor ensures the allocation is freed and state is updated.

Now for perf, we can have the events stick around for a while after the original FD is dead because of references from child events. So we cannot copy the fasync pointer around. We can however consistently use the parent's fasync, as that will be updated.

---
 kernel/events/core.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

@@ -4218,12 +4218,20 @@ static const struct file_operations perf
  * to user-space before waking everybody up.
  */
 
+static inline struct fasync_struct **perf_event_fasync(struct perf_event *event)
+{
+	/* only the parent has fasync state */
+	if (event->parent)
+		event = event->parent;
+	return &event->fasync;
+}
+
 void perf_event_wakeup(struct perf_event *event)
 {
 	ring_buffer_wakeup(event);
 
 	if (event->pending_kill) {
-		kill_fasync(&event->fasync, SIGIO, event->pending_kill);
+		kill_fasync(perf_event_fasync(event), SIGIO, event->pending_kill);
 		event->pending_kill = 0;
 	}
 }

@@ -5432,7 +5440,7 @@ static int __perf_event_overflow(struct
 	else
 		perf_event_output(event, data, regs);
 
-	if (event->fasync && event->pending_kill) {
+	if (*perf_event_fasync(event) && event->pending_kill) {
 		event->pending_wakeup = 1;
 		irq_work_queue(&event->pending);
 	}

Patches currently in stable-queue which might be from [email protected] are

queue-3.14/perf-fix-perf_event_ioc_period-migration-race.patch queue-3.14/ipc-sem.c-update-correct-memory-barriers.patch queue-3.14/perf-fix-fasync-handling-on-inherited-events.patch