[patch 03/15] clocksource: Let timekeeping_notify return success/error

[Thomas Gleixner]

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@xxxxxxxxxxxxx>
---
 include/linux/clocksource.h |    2 +-
 kernel/time/clocksource.c   |    6 +++---
 kernel/time/timekeeping.c   |    5 +++--
 3 files changed, 7 insertions(+), 6 deletions(-)

Index: tip/include/linux/clocksource.h
===================================================================
--- tip.orig/include/linux/clocksource.h
+++ tip/include/linux/clocksource.h
@@ -321,7 +321,7 @@ static inline void __clocksource_updatef
 }
 
 
-extern void timekeeping_notify(struct clocksource *clock);
+extern int timekeeping_notify(struct clocksource *clock);
 
 extern cycle_t clocksource_mmio_readl_up(struct clocksource *);
 extern cycle_t clocksource_mmio_readl_down(struct clocksource *);
Index: tip/kernel/time/clocksource.c
===================================================================
--- tip.orig/kernel/time/clocksource.c
+++ tip/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);
 	}
 }
 
Index: tip/kernel/time/timekeeping.c
===================================================================
--- tip.orig/kernel/time/timekeeping.c
+++ tip/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;
 }
 
 /**


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