1 files changed, 26 insertions, 17 deletions

diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index b08722de610c..df884022fbd9 100644
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -145,22 +145,40 @@ 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
+ * can_attach() result will remain valid until the attach completes.
+ */
 static int freezer_can_attach(struct cgroup_subsys *ss,
                               struct cgroup *new_cgroup,
                               struct task_struct *task)
 {
         struct freezer *freezer;
-        int retval = 0;
+        int retval;
+
+        /* Anything frozen can't move or be moved to/from */
+
+        if (is_task_frozen_enough(task))
+                return -EBUSY;
 
-        /*
-         * The call to cgroup_lock() in the freezer.state write method prevents
-         * a write to that file racing against an attach, and hence the
-         * can_attach() result will remain valid until the attach completes.
-         */
         freezer = cgroup_freezer(new_cgroup);
         if (freezer->state == STATE_FROZEN)
+                return -EBUSY;
+
+        retval = 0;
+        task_lock(task);
+        freezer = task_freezer(task);
+        if (freezer->state == STATE_FROZEN)
                 retval = -EBUSY;
+        task_unlock(task);
         return retval;
 }
 
@@ -193,12 +211,7 @@ static void check_if_frozen(struct cgroup *cgroup,
         cgroup_iter_start(cgroup, &it);
         while ((task = cgroup_iter_next(cgroup, &it))) {
                 ntotal++;
-                /*
-                 * Task is frozen or will freeze immediately when next it gets
-                 * woken
-                 */
-                if (frozen(task) ||
-                    (task_is_stopped_or_traced(task) && freezing(task)))
+                if (is_task_frozen_enough(task))
                         nfrozen++;
         }
 
@@ -249,11 +262,7 @@ 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 (task_is_stopped_or_traced(task) && freezing(task))
-                        /*
-                         * The freeze flag is set so these tasks will
-                         * immediately go into the fridge upon waking.
-                         */
+                if (is_task_frozen_enough(task))
                         continue;
                 if (!freezing(task) && !freezer_should_skip(task))
                         num_cant_freeze_now++;