4.9-stable review patch. If anyone has any objections, please let me know.
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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;