[PATCH] i386: Detect clock skew during suspend

Detect the situations in which the time after a resume from disk would be
earlier than the time before the suspend and prevent them from happening on
i386.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: John Stultz <johnstul@us.ibm.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 18 insertions, 6 deletions

diff --git a/arch/i386/kernel/time.c b/arch/i386/kernel/time.c
index 6f333e7fb23c..1302e4ab3c4f 100644
--- a/arch/i386/kernel/time.c
+++ b/arch/i386/kernel/time.c
@@ -270,16 +270,19 @@ void notify_arch_cmos_timer(void)
         mod_timer(&sync_cmos_timer, jiffies + 1);
 }
 
-static long clock_cmos_diff, sleep_start;
+static long clock_cmos_diff;
+static unsigned long sleep_start;
 
 static int timer_suspend(struct sys_device *dev, pm_message_t state)
 {
         /*
          * Estimate time zone so that set_time can update the clock
          */
-        clock_cmos_diff = -get_cmos_time();
+        unsigned long ctime =  get_cmos_time();
+
+        clock_cmos_diff = -ctime;
         clock_cmos_diff += get_seconds();
-        sleep_start = get_cmos_time();
+        sleep_start = ctime;
         return 0;
 }
 
@@ -287,16 +290,25 @@ static int timer_resume(struct sys_device *dev)
 {
         unsigned long flags;
         unsigned long sec;
-        unsigned long sleep_length;
+        unsigned long ctime = get_cmos_time();
+        long sleep_length = (ctime - sleep_start) * HZ;
         struct timespec ts;
+
+        if (sleep_length < 0) {
+                printk(KERN_WARNING "CMOS clock skew detected in timer resume!\n");
+                /* The time after the resume must not be earlier than the time
+                 * before the suspend or some nasty things will happen
+                 */
+                sleep_length = 0;
+                ctime = sleep_start;
+        }
 #ifdef CONFIG_HPET_TIMER
         if (is_hpet_enabled())
                 hpet_reenable();
 #endif
         setup_pit_timer();
-        sec = get_cmos_time() + clock_cmos_diff;
-        sleep_length = (get_cmos_time() - sleep_start) * HZ;
 
+        sec = ctime + clock_cmos_diff;
         ts.tv_sec = sec;
         ts.tv_nsec = 0;
         do_settimeofday(&ts);