Patch "timers, sched_clock: Update timeout for clock wrap" has been added to the 3.18-stable tree

Patch "timers, sched_clock: Update timeout for clock wrap" has been added to the 3.18-stable tree

[gregkh]

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 3.18-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-3.18 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 10:11:52 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
@@ -146,6 +146,11 @@ void __init sched_clock_register(u64 (*r
 	cd.epoch_ns = ns;
 	raw_write_seqcount_end(&cd.seq);
 
+	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-3.18/timers-sched_clock-update-timeout-for-clock-wrap.patch