1 files changed, 17 insertions, 26 deletions

diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index 0b0e10545ef0..3d45503a21a2 100644
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -213,41 +213,39 @@ out:
 }
 
 /*
- * caller must hold freezer->lock
+ * We change from FREEZING to FROZEN lazily if the cgroup was only
+ * partially frozen when we exitted write.  Caller must hold freezer->lock.
+ *
+ * Task states and freezer state might disagree while tasks are being
+ * migrated into @cgroup, so we can't verify task states against @freezer
+ * state here.  See freezer_attach() for details.
  */
-static void update_if_frozen(struct cgroup *cgroup,
-				 struct freezer *freezer)
+static void update_if_frozen(struct cgroup *cgroup, struct freezer *freezer)
 {
 	struct cgroup_iter it;
 	struct task_struct *task;
-	unsigned int nfrozen = 0, ntotal = 0;
-	enum freezer_state old_state = freezer->state;
+
+	if (freezer->state != CGROUP_FREEZING)
+		return;
 
 	cgroup_iter_start(cgroup, &it);
+
 	while ((task = cgroup_iter_next(cgroup, &it))) {
 		if (freezing(task)) {
-			ntotal++;
 			/*
 			 * freezer_should_skip() indicates that the task
 			 * should be skipped when determining freezing
 			 * completion.  Consider it frozen in addition to
 			 * the usual frozen condition.
 			 */
-			if (frozen(task) || task_is_stopped_or_traced(task) ||
-			    freezer_should_skip(task))
-				nfrozen++;
+			if (!frozen(task) && !task_is_stopped_or_traced(task) &&
+			    !freezer_should_skip(task))
+				goto notyet;
 		}
 	}
 
-	if (old_state == CGROUP_THAWED) {
-		BUG_ON(nfrozen > 0);
-	} else if (old_state == CGROUP_FREEZING) {
-		if (nfrozen == ntotal)
-			freezer->state = CGROUP_FROZEN;
-	} else { /* old_state == CGROUP_FROZEN */
-		BUG_ON(nfrozen != ntotal);
-	}
-
+	freezer->state = CGROUP_FROZEN;
+notyet:
 	cgroup_iter_end(cgroup, &it);
 }
 
@@ -262,13 +260,8 @@ static int freezer_read(struct cgroup *cgroup, struct cftype *cft,
 
 	freezer = cgroup_freezer(cgroup);
 	spin_lock_irq(&freezer->lock);
+	update_if_frozen(cgroup, freezer);
 	state = freezer->state;
-	if (state == CGROUP_FREEZING) {
-		/* We change from FREEZING to FROZEN lazily if the cgroup was
-		 * only partially frozen when we exitted write. */
-		update_if_frozen(cgroup, freezer);
-		state = freezer->state;
-	}
 	spin_unlock_irq(&freezer->lock);
 	cgroup_unlock();
 
@@ -306,8 +299,6 @@ static void freezer_change_state(struct cgroup *cgroup,
 
 	spin_lock_irq(&freezer->lock);
 
-	update_if_frozen(cgroup, freezer);
-
 	switch (goal_state) {
 	case CGROUP_THAWED:
 		if (freezer->state != CGROUP_THAWED)