clocksource: clocksource_select must be called with mutex locked

The callers of clocksource_select must hold clocksource_mutex to
protect the clocksource_list.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <new-submission>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 5697155..2c2e5ba 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -471,7 +471,9 @@
 static int __init clocksource_done_booting(void)
 {
 	finished_booting = 1;
+	mutex_lock(&clocksource_mutex);
 	clocksource_select();
+	mutex_unlock(&clocksource_mutex);
 	return 0;
 }
 fs_initcall(clocksource_done_booting);