diff mbox

[2/2] time: Fix change_clocksource locking

Message ID 1331769536-4602-3-git-send-email-john.stultz@linaro.org
State Accepted
Headers show

Commit Message

John Stultz March 14, 2012, 11:58 p.m. UTC 
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 <luto@amacapital.net>
CC: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
 kernel/time/timekeeping.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)
diff mbox

Patch

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 403c2a0..b53da5e 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -448,9 +448,12 @@  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;
@@ -458,6 +461,10 @@  static int change_clocksource(void *data)
 		if (old->disable)
 			old->disable(old);
 	}
+	timekeeping_update(true);
+
+	write_sequnlock_irqrestore(&timekeeper.lock, flags);
+
 	return 0;
 }