time: Fix change_clocksource locking

change_clocksource() fails to grab locks or call timekeeping_update(), which leaves a race window for time inconsistencies. This adds proper locking and a call to timekeeping_update() to fix this. CC: Andy Lutomirski <[email protected]> CC: Thomas Gleixner <[email protected]> Signed-off-by: John Stultz <[email protected]>
VadimAlexeev · Mar 16, 2012 · f695cf9 · f695cf9
1 parent a939e81
commit f695cf9
Showing 1 changed file with 7 additions and 0 deletions.
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
@@ -448,16 +448,23 @@ EXPORT_SYMBOL(timekeeping_inject_offset);
 static int change_clocksource(void *data)
 {
 	struct clocksource *new, *old;
+	unsigned long flags;
 
 	new = (struct clocksource *) data;
 
+	write_seqlock_irqsave(&timekeeper.lock, flags);
+
 	timekeeping_forward_now();
 	if (!new->enable || new->enable(new) == 0) {
 		old = timekeeper.clock;
 		timekeeper_setup_internals(new);
 		if (old->disable)
 			old->disable(old);
 	}
+	timekeeping_update(true);
+
+	write_sequnlock_irqrestore(&timekeeper.lock, flags);
+
 	return 0;
 }