clocksource: Consistent de-rate when marking unstable

When a registered clocksource gets marked unstable the watchdog_kthread
will de-rate and re-select the clocksource. Ensure it also de-rates
when getting called on an unregistered clocksource.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: len.brown@intel.com
Cc: rjw@rjwysocki.net
Cc: diego.viola@gmail.com
Cc: rui.zhang@intel.com
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20180430100344.594904898@infradead.org

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 935f39eb8aac33029569f51bff92cff5c8c6c479..605656df16c413fd8ed523c672c2713880829693 100644 (file)
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -152,12 +152,19 @@ static void __clocksource_unstable(struct clocksource *cs)
        cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
        cs->flags |= CLOCK_SOURCE_UNSTABLE;
 
-       if (list_empty(&cs->list))
+       /*
+        * If the clocksource is registered clocksource_watchdog_kthread() will
+        * re-rate and re-select.
+        */
+       if (list_empty(&cs->list)) {
+               cs->rating = 0;
                return;
+       }
 
        if (cs->mark_unstable)
                cs->mark_unstable(cs);
 
+       /* kick clocksource_watchdog_kthread() */
        if (finished_booting)
                schedule_work(&watchdog_work);
 }