Patch "timers, sched_clock: Update timeout for clock wrap" has been added to the 4.4-stable tree

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

timers, sched_clock: Update timeout for clock wrap

to the 4.4-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:
timers-sched_clock-update-timeout-for-clock-wrap.patch
and it can be found in the queue-4.4 subdirectory.

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

From: David Engraf <[email protected]>
Date: Fri, 17 Feb 2017 08:51:03 +0100
Subject: timers, sched_clock: Update timeout for clock wrap

From: David Engraf <[email protected]>

[ Upstream commit 1b8955bc5ac575009835e371ae55e7f3af2197a9 ]

The scheduler clock framework may not use the correct timeout for the clock wrap. This happens when a new clock driver calls sched_clock_register() after the kernel called sched_clock_postinit(). In this case the clock wrap timeout is too long thus sched_clock_poll() is called too late and the clock already wrapped.

On my ARM system the scheduler was no longer scheduling any other task than the idle task because the sched_clock() wrapped.

---
 kernel/time/sched_clock.c |    5 +++++
 1 file changed, 5 insertions(+)

@@ -205,6 +205,11 @@ sched_clock_register(u64 (*read)(void),
 
 	update_clock_read_data(&rd);
 
+	if (sched_clock_timer.function != NULL) {
+		/* update timeout for clock wrap */
+		hrtimer_start(&sched_clock_timer, cd.wrap_kt, HRTIMER_MODE_REL);
+	}
+
 	r = rate;
 	if (r >= 4000000) {
 		r /= 1000000;

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

queue-4.4/timers-sched_clock-update-timeout-for-clock-wrap.patch