cgroup: fix rmdir EBUSY regression in 3.11

[karo-tx-linux.git] / kernel / cgroup.c

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 781845a013ab23c8f99f2c2153c70c9fd679c45d..e91963302c0d5a31c57401dfacb4bd15b8f47a79 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4480,6 +4480,7 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
        struct dentry *d = cgrp->dentry;
        struct cgroup_event *event, *tmp;
        struct cgroup_subsys *ss;
+       struct cgroup *child;
        bool empty;
 
        lockdep_assert_held(&d->d_inode->i_mutex);
@@ -4490,11 +4491,27 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
         * @cgrp from being removed while __put_css_set() is in progress.
         */
        read_lock(&css_set_lock);
-       empty = list_empty(&cgrp->cset_links) && list_empty(&cgrp->children);
+       empty = list_empty(&cgrp->cset_links);
        read_unlock(&css_set_lock);
        if (!empty)
                return -EBUSY;
 
+       /*
+        * Make sure there's no live children.  We can't test ->children
+        * emptiness as dead children linger on it while being destroyed;
+        * otherwise, "rmdir parent/child parent" may fail with -EBUSY.
+        */
+       empty = true;
+       rcu_read_lock();
+       list_for_each_entry_rcu(child, &cgrp->children, sibling) {
+               empty = cgroup_is_dead(child);
+               if (!empty)
+                       break;
+       }
+       rcu_read_unlock();
+       if (!empty)
+               return -EBUSY;
+
        /*
         * Block new css_tryget() by killing css refcnts.  cgroup core
         * guarantees that, by the time ->css_offline() is invoked, no new