PM: Allow wakeup events to abort freezing of tasks

If there is a wakeup event during the freezing of tasks, suspend or
hibernation will fail anyway.  Since try_to_freeze_tasks() can take
up to 20 seconds to complete or fail, aborting it as soon as a wakeup
event is detected improves the worst case wakeup latency.

Based on a patch from Arve Hjønnevåg.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>

2 files changed, 11 insertions, 2 deletions

diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index 6b1712c51102..26697514c5ec 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -308,6 +308,8 @@ static inline int unregister_pm_notifier(struct notifier_block *nb)
 }
 
 #define pm_notifier(fn, pri)    do { (void)(fn); } while (0)
+
+static inline bool pm_check_wakeup_events(void) { return true; }
 #endif /* !CONFIG_PM_SLEEP */
 
 extern struct mutex pm_mutex;
diff --git a/kernel/power/process.c b/kernel/power/process.c
index 028a99598f49..e50b4c1b2a0f 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -40,6 +40,7 @@ static int try_to_freeze_tasks(bool sig_only)
         struct timeval start, end;
         u64 elapsed_csecs64;
         unsigned int elapsed_csecs;
+        bool wakeup = false;
 
         do_gettimeofday(&start);
 
@@ -78,6 +79,11 @@ static int try_to_freeze_tasks(bool sig_only)
                 if (!todo || time_after(jiffies, end_time))
                         break;
 
+                if (!pm_check_wakeup_events()) {
+                        wakeup = true;
+                        break;
+                }
+
                 /*
                  * We need to retry, but first give the freezing tasks some
                  * time to enter the regrigerator.
@@ -97,8 +103,9 @@ static int try_to_freeze_tasks(bool sig_only)
                  * but it cleans up leftover PF_FREEZE requests.
                  */
                 printk("\n");
-                printk(KERN_ERR "Freezing of tasks failed after %d.%02d seconds "
+                printk(KERN_ERR "Freezing of tasks %s after %d.%02d seconds "
                        "(%d tasks refusing to freeze, wq_busy=%d):\n",
+                       wakeup ? "aborted" : "failed",
                        elapsed_csecs / 100, elapsed_csecs % 100,
                        todo - wq_busy, wq_busy);
 
@@ -107,7 +114,7 @@ static int try_to_freeze_tasks(bool sig_only)
                 read_lock(&tasklist_lock);
                 do_each_thread(g, p) {
                         task_lock(p);
-                        if (freezing(p) && !freezer_should_skip(p))
+                        if (!wakeup && freezing(p) && !freezer_should_skip(p))
                                 sched_show_task(p);
                         cancel_freezing(p);
                         task_unlock(p);