1 files changed, 32 insertions, 40 deletions

diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index ce71ed53e88f..e7bebb7c6c38 100644
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -48,20 +48,19 @@ static inline struct freezer *task_freezer(struct task_struct *task)
                             struct freezer, css);
 }
 
-int cgroup_freezing_or_frozen(struct task_struct *task)
+static inline int __cgroup_freezing_or_frozen(struct task_struct *task)
 {
-        struct freezer *freezer;
-        enum freezer_state state;
+        enum freezer_state state = task_freezer(task)->state;
+        return (state == CGROUP_FREEZING) || (state == CGROUP_FROZEN);
+}
 
+int cgroup_freezing_or_frozen(struct task_struct *task)
+{
+        int result;
         task_lock(task);
-        freezer = task_freezer(task);
-        if (!freezer->css.cgroup->parent)
-                state = CGROUP_THAWED; /* root cgroup can't be frozen */
-        else
-                state = freezer->state;
+        result = __cgroup_freezing_or_frozen(task);
         task_unlock(task);
-
-        return (state == CGROUP_FREEZING) || (state == CGROUP_FROZEN);
+        return result;
 }
 
 /*
@@ -154,13 +153,6 @@ static void freezer_destroy(struct cgroup_subsys *ss,
         kfree(cgroup_freezer(cgroup));
 }
 
-/* Task is frozen or will freeze immediately when next it gets woken */
-static bool is_task_frozen_enough(struct task_struct *task)
-{
-        return frozen(task) ||
-                (task_is_stopped_or_traced(task) && freezing(task));
-}
-
 /*
  * The call to cgroup_lock() in the freezer.state write method prevents
  * a write to that file racing against an attach, and hence the
@@ -174,24 +166,25 @@ static int freezer_can_attach(struct cgroup_subsys *ss,
 
         /*
          * 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))
+        freezer = cgroup_freezer(new_cgroup);
+        if (freezer->state != CGROUP_THAWED)
                 return -EBUSY;
 
-        freezer = cgroup_freezer(new_cgroup);
-        if (freezer->state == CGROUP_FROZEN)
+        rcu_read_lock();
+        if (__cgroup_freezing_or_frozen(task)) {
+                rcu_read_unlock();
                 return -EBUSY;
+        }
+        rcu_read_unlock();
 
         if (threadgroup) {
                 struct task_struct *c;
 
                 rcu_read_lock();
                 list_for_each_entry_rcu(c, &task->thread_group, thread_group) {
-                        if (is_task_frozen_enough(c)) {
+                        if (__cgroup_freezing_or_frozen(c)) {
                                 rcu_read_unlock();
                                 return -EBUSY;
                         }
@@ -236,31 +229,30 @@ static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task)
 /*
  * caller must hold freezer->lock
  */
-static void update_freezer_state(struct cgroup *cgroup,
+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;
 
         cgroup_iter_start(cgroup, &it);
         while ((task = cgroup_iter_next(cgroup, &it))) {
                 ntotal++;
-                if (is_task_frozen_enough(task))
+                if (frozen(task))
                         nfrozen++;
         }
 
-        /*
-         * Transition to FROZEN when no new tasks can be added ensures
-         * that we never exist in the FROZEN state while there are unfrozen
-         * tasks.
-         */
-        if (nfrozen == ntotal)
-                freezer->state = CGROUP_FROZEN;
-        else if (nfrozen > 0)
-                freezer->state = CGROUP_FREEZING;
-        else
-                freezer->state = CGROUP_THAWED;
+        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);
+        }
+
         cgroup_iter_end(cgroup, &it);
 }
 
@@ -279,7 +271,7 @@ static int freezer_read(struct cgroup *cgroup, struct cftype *cft,
         if (state == CGROUP_FREEZING) {
                 /* We change from FREEZING to FROZEN lazily if the cgroup was
                  * only partially frozen when we exitted write. */
-                update_freezer_state(cgroup, freezer);
+                update_if_frozen(cgroup, freezer);
                 state = freezer->state;
         }
         spin_unlock_irq(&freezer->lock);
@@ -301,7 +293,7 @@ static int try_to_freeze_cgroup(struct cgroup *cgroup, struct freezer *freezer)
         while ((task = cgroup_iter_next(cgroup, &it))) {
                 if (!freeze_task(task, true))
                         continue;
-                if (is_task_frozen_enough(task))
+                if (frozen(task))
                         continue;
                 if (!freezing(task) && !freezer_should_skip(task))
                         num_cant_freeze_now++;
@@ -335,7 +327,7 @@ static int freezer_change_state(struct cgroup *cgroup,
 
         spin_lock_irq(&freezer->lock);
 
-        update_freezer_state(cgroup, freezer);
+        update_if_frozen(cgroup, freezer);
         if (goal_state == freezer->state)
                 goto out;