Re: [PATCH] fix potential jiffies overflow

[Atsushi Nemoto <anemo@mba.ocn.ne.jp>]

>>>>> On Thu, 2 Mar 2006 10:43:12 -0600, "Ram Gupta" <ram.gupta5@gmail.com> said:
>> I found i386 timer_resume is updating jiffies, not jiffies_64.  It
>> looks there is a potential overflow problem.  Is this a correct
>> fix?

ram> The 64-bit jiffies value is not atomic. You need to hold
ram> xtime_lock to read it.

OK, and I guess wall_jiffies also needs xtime_lock.


I found i386 timer_resume is updating jiffies, not jiffies_64.  It
looks there is a potential overflow problem.  And jiffies_64 and
wall_jiffies should be protected by xtime_lock.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>

diff --git a/arch/i386/kernel/time.c b/arch/i386/kernel/time.c
index a14d594..9d30747 100644
--- a/arch/i386/kernel/time.c
+++ b/arch/i386/kernel/time.c
@@ -412,9 +412,9 @@ static int timer_resume(struct sys_devic
 	write_seqlock_irqsave(&xtime_lock, flags);
 	xtime.tv_sec = sec;
 	xtime.tv_nsec = 0;
-	write_sequnlock_irqrestore(&xtime_lock, flags);
-	jiffies += sleep_length;
+	jiffies_64 += sleep_length;
 	wall_jiffies += sleep_length;
+	write_sequnlock_irqrestore(&xtime_lock, flags);
 	if (last_timer->resume)
 		last_timer->resume();
 	cur_timer = last_timer;
-
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