1 files changed, 24 insertions, 18 deletions

diff --git a/kernel/freezer.c b/kernel/freezer.c
index 4130e48..a8822be 100644
--- a/kernel/freezer.c
+++ b/kernel/freezer.c
@@ -22,14 +22,19 @@ bool __refrigerator(bool check_kthr_stop)
 	bool was_frozen = false;
 	long save;
 
+	/*
+	 * Enter FROZEN.  If NOFREEZE, schedule immediate thawing by
+	 * clearing freezing.
+	 */
 	spin_lock_irq(&freezer_lock);
+repeat:
 	if (!freezing(current)) {
 		spin_unlock_irq(&freezer_lock);
 		return was_frozen;
 	}
-	if (!(current->flags & PF_NOFREEZE))
-		current->flags |= PF_FROZEN;
-	clear_freeze_flag(current);
+	if (current->flags & PF_NOFREEZE)
+		clear_freeze_flag(current);
+	current->flags |= PF_FROZEN;
 	spin_unlock_irq(&freezer_lock);
 
 	save = current->state;
@@ -44,7 +49,7 @@ bool __refrigerator(bool check_kthr_stop)
 
 	for (;;) {
 		set_current_state(TASK_UNINTERRUPTIBLE);
-		if (!frozen(current) ||
+		if (!freezing(current) ||
 		    (check_kthr_stop && kthread_should_stop()))
 			break;
 		was_frozen = true;
@@ -54,6 +59,13 @@ bool __refrigerator(bool check_kthr_stop)
 	/* Remove the accounting blocker */
 	current->flags &= ~PF_FREEZING;
 
+	/* leave FROZEN */
+	spin_lock_irq(&freezer_lock);
+	if (freezing(current))
+		goto repeat;
+	current->flags &= ~PF_FROZEN;
+	spin_unlock_irq(&freezer_lock);
+
 	pr_debug("%s left refrigerator\n", current->comm);
 
 	/*
@@ -137,25 +149,19 @@ void cancel_freezing(struct task_struct *p)
 	spin_unlock_irqrestore(&freezer_lock, flags);
 }
 
-/*
- * Wake up a frozen task
- *
- * task_lock() is needed to prevent the race with refrigerator() which may
- * occur if the freezing of tasks fails.  Namely, without the lock, if the
- * freezing of tasks failed, thaw_tasks() might have run before a task in
- * refrigerator() could call frozen_process(), in which case the task would be
- * frozen and no one would thaw it.
- */
 void __thaw_task(struct task_struct *p)
 {
 	unsigned long flags;
 
+	/*
+	 * Clear freezing and kick @p if FROZEN.  Clearing is guaranteed to
+	 * be visible to @p as waking up implies wmb.  Waking up inside
+	 * freezer_lock also prevents wakeups from leaking outside
+	 * refrigerator.
+	 */
 	spin_lock_irqsave(&freezer_lock, flags);
-	if (frozen(p)) {
-		p->flags &= ~PF_FROZEN;
+	clear_freeze_flag(p);
+	if (frozen(p))
 		wake_up_process(p);
-	} else {
-		clear_freeze_flag(p);
-	}
 	spin_unlock_irqrestore(&freezer_lock, flags);
 }