[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>

diff --git a/arch/i386/kernel/time.c b/arch/i386/kernel/time.c
index 6f333e7..1302e4a 100644 (file)
--- 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);