[3.16.y-ckt stable] Patch "perf: Fix fasync handling on inherited events" has been added to staging queue

Luis Henriques luis.henriques at canonical.com
Thu Sep 3 10:37:30 UTC 2015


This is a note to let you know that I have just added a patch titled

    perf: Fix fasync handling on inherited events

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt17.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From aef4cb0e6cda3543423e49b4c65fce762d30f27c Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz at infradead.org>
Date: Thu, 11 Jun 2015 10:32:01 +0200
Subject: perf: Fix fasync handling on inherited events

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.

Reported-and-Tested-by: Vince Weaver <vincent.weaver at maine.edu>
Signed-off-by: Peter Zijlstra (Intel) <peterz at infradead.org>
Cc: Arnaldo Carvalho deMelo <acme at kernel.org>
Cc: Linus Torvalds <torvalds at linux-foundation.org>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: eranian at google.com
Link: http://lkml.kernel.org/r/1434011521.1495.71.camel@twins
Signed-off-by: Ingo Molnar <mingo at kernel.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 kernel/events/core.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 40338799dcb0..944d6b5eaf17 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4285,12 +4285,20 @@ static const struct file_operations perf_fops = {
  * 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;
 	}
 }
@@ -5519,7 +5527,7 @@ static int __perf_event_overflow(struct perf_event *event,
 	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);
 	}




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