clocksource: Let timekeeping_notify return success/error

timekeeping_notify() can fail due cs->enable() failure. Though the
caller does not notice and happily keeps the wrong clocksource as the
current one.

Let the caller know about failure, so the current clocksource will be
shown correctly in sysfs.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <john.stultz@linaro.org>
Cc: Magnus Damm <magnus.damm@gmail.com>
Link: http://lkml.kernel.org/r/20130425143435.696321912@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 6 insertions, 5 deletions

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index dda5c7130d93..1923a340bd91 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -611,10 +611,10 @@ static void clocksource_select(void)
                         best = cs;
                 break;
         }
-        if (curr_clocksource != best) {
-                printk(KERN_INFO "Switching to clocksource %s\n", best->name);
+
+        if (curr_clocksource != best && !timekeeping_notify(best)) {
+                pr_info("Switched to clocksource %s\n", best->name);
                 curr_clocksource = best;
-                timekeeping_notify(curr_clocksource);
         }
 }
 
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 98cd470bbe49..da6e10c7a378 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -648,14 +648,15 @@ static int change_clocksource(void *data)
  * This function is called from clocksource.c after a new, better clock
  * source has been registered. The caller holds the clocksource_mutex.
  */
-void timekeeping_notify(struct clocksource *clock)
+int timekeeping_notify(struct clocksource *clock)
 {
         struct timekeeper *tk = &timekeeper;
 
         if (tk->clock == clock)
-                return;
+                return 0;
         stop_machine(change_clocksource, clock, NULL);
         tick_clock_notify();
+        return tk->clock == clock ? 0 : -1;
 }
 
 /**