1 files changed, 35 insertions, 35 deletions

diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index e950569..fb249e2 100644
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -162,9 +162,13 @@ static int freezer_can_attach(struct cgroup_subsys *ss,
 			      struct task_struct *task)
 {
 	struct freezer *freezer;
-	int retval;
 
-	/* Anything frozen can't move or be moved to/from */
+	/*
+	 * Anything frozen can't move or be moved to/from.
+	 *
+	 * Since orig_freezer->state == FROZEN means that @task has been
+	 * frozen, so it's sufficient to check the latter condition.
+	 */
 
 	if (is_task_frozen_enough(task))
 		return -EBUSY;
@@ -173,25 +177,31 @@ static int freezer_can_attach(struct cgroup_subsys *ss,
 	if (freezer->state == CGROUP_FROZEN)
 		return -EBUSY;
 
-	retval = 0;
-	task_lock(task);
-	freezer = task_freezer(task);
-	if (freezer->state == CGROUP_FROZEN)
-		retval = -EBUSY;
-	task_unlock(task);
-	return retval;
+	return 0;
 }
 
 static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task)
 {
 	struct freezer *freezer;
 
-	task_lock(task);
+	/*
+	 * No lock is needed, since the task isn't on tasklist yet,
+	 * so it can't be moved to another cgroup, which means the
+	 * freezer won't be removed and will be valid during this
+	 * function call.
+	 */
 	freezer = task_freezer(task);
-	task_unlock(task);
 
-	BUG_ON(freezer->state == CGROUP_FROZEN);
+	/*
+	 * The root cgroup is non-freezable, so we can skip the
+	 * following check.
+	 */
+	if (!freezer->css.cgroup->parent)
+		return;
+
 	spin_lock_irq(&freezer->lock);
+	BUG_ON(freezer->state == CGROUP_FROZEN);
+
 	/* Locking avoids race with FREEZING -> THAWED transitions. */
 	if (freezer->state == CGROUP_FREEZING)
 		freeze_task(task, true);
@@ -276,25 +286,18 @@ static int try_to_freeze_cgroup(struct cgroup *cgroup, struct freezer *freezer)
 	return num_cant_freeze_now ? -EBUSY : 0;
 }
 
-static int unfreeze_cgroup(struct cgroup *cgroup, struct freezer *freezer)
+static void unfreeze_cgroup(struct cgroup *cgroup, struct freezer *freezer)
 {
 	struct cgroup_iter it;
 	struct task_struct *task;
 
 	cgroup_iter_start(cgroup, &it);
 	while ((task = cgroup_iter_next(cgroup, &it))) {
-		int do_wake;
-
-		task_lock(task);
-		do_wake = __thaw_process(task);
-		task_unlock(task);
-		if (do_wake)
-			wake_up_process(task);
+		thaw_process(task);
 	}
 	cgroup_iter_end(cgroup, &it);
-	freezer->state = CGROUP_THAWED;
 
-	return 0;
+	freezer->state = CGROUP_THAWED;
 }
 
 static int freezer_change_state(struct cgroup *cgroup,
@@ -304,27 +307,22 @@ static int freezer_change_state(struct cgroup *cgroup,
 	int retval = 0;
 
 	freezer = cgroup_freezer(cgroup);
+
 	spin_lock_irq(&freezer->lock);
+
 	update_freezer_state(cgroup, freezer);
 	if (goal_state == freezer->state)
 		goto out;
-	switch (freezer->state) {
+
+	switch (goal_state) {
 	case CGROUP_THAWED:
-		retval = try_to_freeze_cgroup(cgroup, freezer);
+		unfreeze_cgroup(cgroup, freezer);
 		break;
-	case CGROUP_FREEZING:
-		if (goal_state == CGROUP_FROZEN) {
-			/* Userspace is retrying after
-			 * "/bin/echo FROZEN > freezer.state" returned -EBUSY */
-			retval = try_to_freeze_cgroup(cgroup, freezer);
-			break;
-		}
-		/* state == FREEZING and goal_state == THAWED, so unfreeze */
 	case CGROUP_FROZEN:
-		retval = unfreeze_cgroup(cgroup, freezer);
+		retval = try_to_freeze_cgroup(cgroup, freezer);
 		break;
 	default:
-		break;
+		BUG();
 	}
 out:
 	spin_unlock_irq(&freezer->lock);
@@ -344,7 +342,7 @@ static int freezer_write(struct cgroup *cgroup,
 	else if (strcmp(buffer, freezer_state_strs[CGROUP_FROZEN]) == 0)
 		goal_state = CGROUP_FROZEN;
 	else
-		return -EIO;
+		return -EINVAL;
 
 	if (!cgroup_lock_live_group(cgroup))
 		return -ENODEV;
@@ -363,6 +361,8 @@ static struct cftype files[] = {
 
 static int freezer_populate(struct cgroup_subsys *ss, struct cgroup *cgroup)
 {
+	if (!cgroup->parent)
+		return 0;
 	return cgroup_add_files(cgroup, ss, files, ARRAY_SIZE(files));
 }