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)