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Message-Id: <1331769536-4602-3-git-send-email-john.stultz@linaro.org>
Date: Wed, 14 Mar 2012 16:58:56 -0700
From: John Stultz <john.stultz@...aro.org>
To: linux-kernel@...r.kernel.org
Cc: John Stultz <john.stultz@...aro.org>,
Andy Lutomirski <luto@...capital.net>,
Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 2/2] 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@...capital.net>
CC: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: John Stultz <john.stultz@...aro.org>
---
kernel/time/timekeeping.c | 7 +++++++
1 files changed, 7 insertions(+), 0 deletions(-)
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;
}
--
1.7.3.2.146.gca209
--
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