[PATCH] 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 x86_64.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Andi Kleen <ak@suse.de>

1 files changed, 9 insertions, 1 deletions

diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
index 97115e608ed8..9dd15d12b659 100644
--- a/arch/x86_64/kernel/time.c
+++ b/arch/x86_64/kernel/time.c
@@ -1039,8 +1039,16 @@ static int timer_resume(struct sys_device *dev)
         unsigned long flags;
         unsigned long sec;
         unsigned long ctime = get_cmos_time();
-        unsigned long sleep_length = (ctime - sleep_start) * HZ;
+        long sleep_length = (ctime - sleep_start) * HZ;
 
+        if (sleep_length < 0) {
+                printk(KERN_WARNING "Time 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;
+        }
         if (vxtime.hpet_address)
                 hpet_reenable();
         else