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| author | Kyle Walker <kwalker@redhat.com> | 2016-08-06 12:07:30 -0400 |
|---|---|---|
| committer | John Stultz <john.stultz@linaro.org> | 2016-08-31 14:43:33 -0700 |
| commit | 36374583f9084cdab4b5dcf5521a3ce55bebb9fa (patch) | |
| tree | 9db17d8912137a810530add26d78f7d67e8462cf /kernel/time/clocksource.c | |
| parent | b4d90e9f1ef1f19dcb2b1b1942c786c9c4225460 (diff) | |
| download | linux-36374583f9084cdab4b5dcf5521a3ce55bebb9fa.tar.gz linux-36374583f9084cdab4b5dcf5521a3ce55bebb9fa.tar.bz2 linux-36374583f9084cdab4b5dcf5521a3ce55bebb9fa.zip | |
clocksource: Defer override invalidation unless clock is unstable
Clocksources don't get the VALID_FOR_HRES flag until they have been
checked by a watchdog. However, when using an override, the
clocksource_select logic will clear the override value if the
clocksource is not marked VALID_FOR_HRES during that inititial check.
When using the boot arguments clocksource=<foo>, this selection can
run before the watchdog, and can cause the override to be incorrectly
cleared.
To address this condition, the override_name is only invalidated for
unstable clocksources. Otherwise, the override is left intact until after
the watchdog has validated the clocksource as stable/unstable.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Kyle Walker <kwalker@redhat.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Diffstat (limited to 'kernel/time/clocksource.c')
| -rw-r--r-- | kernel/time/clocksource.c | 15 |
1 files changed, 12 insertions, 3 deletions
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index 6a5a310a1a53..7e4fad75acaa 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -600,9 +600,18 @@ static void __clocksource_select(bool skipcur) */ if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && oneshot) { /* Override clocksource cannot be used. */ - pr_warn("Override clocksource %s is not HRT compatible - cannot switch while in HRT/NOHZ mode\n", - cs->name); - override_name[0] = 0; + if (cs->flags & CLOCK_SOURCE_UNSTABLE) { + pr_warn("Override clocksource %s is unstable and not HRT compatible - cannot switch while in HRT/NOHZ mode\n", + cs->name); + override_name[0] = 0; + } else { + /* + * The override cannot be currently verified. + * Deferring to let the watchdog check. + */ + pr_info("Override clocksource %s is not currently HRT compatible - deferring\n", + cs->name); + } } else /* Override clocksource can be used. */ best = cs; |