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%3Ba=su...

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 stable@vger.kernel.org know about it.

From foo@baz Mon Mar 19 09:58:12 CET 2018

From: David Engraf david.engraf@sysgo.com Date: Fri, 17 Feb 2017 08:51:03 +0100 Subject: timers, sched_clock: Update timeout for clock wrap

From: David Engraf david.engraf@sysgo.com

[ 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.

Signed-off-by: David Engraf david.engraf@sysgo.com Signed-off-by: John Stultz john.stultz@linaro.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/time/sched_clock.c | 5 +++++ 1 file changed, 5 insertions(+)

--- a/kernel/time/sched_clock.c +++ b/kernel/time/sched_clock.c @@ -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 david.engraf@sysgo.com are

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