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authorJohn Stultz <john.stultz@linaro.org>2012-03-14 16:38:15 -0700
committerJohn Stultz <john.stultz@linaro.org>2012-03-15 18:17:54 -0700
commitf695cf94837de53864180400cbac42cfa370426f (patch)
tree9bb91a9b8c5a1291a083a37e790da00d477b18f8
parenta939e817aa7e199d2fff05a67cb745be32dd5c2d (diff)
downloadlinux-f695cf94837de53864180400cbac42cfa370426f.tar.bz2
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 <luto@amacapital.net> CC: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: John Stultz <john.stultz@linaro.org>
-rw-r--r--kernel/time/timekeeping.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 403c2a092830..b53da5ecbea2 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;
}