sched/clock, clocksource: Add optional cs::mark_unstable() method

PeterZ reported that we'd fail to mark the TSC unstable when the
clocksource watchdog finds it unsuitable.

Allow a clocksource to run a custom action when its being marked
unstable and hook up the TSC unstable code.

Reported-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index e315d04a2fd9..cfc75848a35d 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -62,6 +62,8 @@ struct module;
  * @archdata:           arch-specific data
  * @suspend:            suspend function for the clocksource, if necessary
  * @resume:             resume function for the clocksource, if necessary
+ * @mark_unstable:      Optional function to inform the clocksource driver that
+ *                      the watchdog marked the clocksource unstable
  * @owner:              module reference, must be set by clocksource in modules
  *
  * Note: This struct is not used in hotpathes of the timekeeping code
@@ -93,6 +95,7 @@ struct clocksource {
         unsigned long flags;
         void (*suspend)(struct clocksource *cs);
         void (*resume)(struct clocksource *cs);
+        void (*mark_unstable)(struct clocksource *cs);
 
         /* private: */
 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG