1 files changed, 35 insertions, 35 deletions

diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index e95056954498..fb249e2bcada 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));
 }