[PATCH] time: add barrier after updating jiffies_64

Add a compiler barrier so that we don't read jiffies before updating
jiffies_64.
Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/timer.c

@@ -941,6 +941,8 @@ static inline void update_times(void)
 void do_timer(struct pt_regs *regs)
 {
 	jiffies_64++;
+	/* prevent loading jiffies before storing new jiffies_64 value. */
+	barrier();
 	update_times();
 	softlockup_tick(regs);
 }