From 2208b4afe74cbf398fbed88834b0308e3a86847a Mon Sep 17 00:00:00 2001
From: "Rafael J. Wysocki" <rjw@sisk.pl>
Date: Wed, 23 May 2007 13:57:24 -0700
Subject: [PATCH] --- yaml --- r: 56862 b: refs/heads/master c:
 33e1c288da62a6a5aa9077a6b7bfa690b1b02cf4 h: refs/heads/master v: v3

---
 [refs]                        |  2 +-
 trunk/include/linux/freezer.h | 10 ++++++++++
 trunk/kernel/power/process.c  | 12 +++++++++++-
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/[refs] b/[refs]
index d6fdf842e1df..4c224c98905a 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 585a2858b970cb6e2e5ca4877eefd18b4dba8ed4
+refs/heads/master: 33e1c288da62a6a5aa9077a6b7bfa690b1b02cf4
diff --git a/trunk/include/linux/freezer.h b/trunk/include/linux/freezer.h
index 5e75e26d4787..db5423eae24d 100644
--- a/trunk/include/linux/freezer.h
+++ b/trunk/include/linux/freezer.h
@@ -37,14 +37,24 @@ static inline void do_not_freeze(struct task_struct *p)
 
 /*
  * Wake up a frozen process
+ *
+ * task_lock() is taken 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.
  */
 static inline int thaw_process(struct task_struct *p)
 {
+	task_lock(p);
 	if (frozen(p)) {
 		p->flags &= ~PF_FROZEN;
+		task_unlock(p);
 		wake_up_process(p);
 		return 1;
 	}
+	clear_tsk_thread_flag(p, TIF_FREEZE);
+	task_unlock(p);
 	return 0;
 }
 
diff --git a/trunk/kernel/power/process.c b/trunk/kernel/power/process.c
index 088419387388..02e490e311eb 100644
--- a/trunk/kernel/power/process.c
+++ b/trunk/kernel/power/process.c
@@ -37,10 +37,18 @@ void refrigerator(void)
 	/* Hmm, should we be allowed to suspend when there are realtime
 	   processes around? */
 	long save;
+
+	task_lock(current);
+	if (freezing(current)) {
+		frozen_process(current);
+		task_unlock(current);
+	} else {
+		task_unlock(current);
+		return;
+	}
 	save = current->state;
 	pr_debug("%s entered refrigerator\n", current->comm);
 
-	frozen_process(current);
 	spin_lock_irq(&current->sighand->siglock);
 	recalc_sigpending(); /* We sent fake signal, clean it up */
 	spin_unlock_irq(&current->sighand->siglock);
@@ -152,10 +160,12 @@ static unsigned int try_to_freeze_tasks(int freeze_user_space)
 			if (is_user_space(p) == !freeze_user_space)
 				continue;
 
+			task_lock(p);
 			if (freezeable(p) && !frozen(p))
 				printk(KERN_ERR " %s\n", p->comm);
 
 			cancel_freezing(p);
+			task_unlock(p);
 		} while_each_thread(g, p);
 		read_unlock(&tasklist_lock);
 	}