---

yaml
---
r: 339359
b: refs/heads/master
c: 205a872
h: refs/heads/master
i:
  339357: b1229e0
  339355: 7e03b41
  339351: 563da2d
  339343: 1e25a39
  339327: 03f752c
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: fddfb02ad0d0d3b479c2a26a8ae7e6411b34706b
+refs/heads/master: 205a872bd6f9a9a09ef035ef1e90185a8245cc58

trunk/kernel/cgroup.c

@@ -4277,6 +4277,7 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
 	DEFINE_WAIT(wait);
 	struct cgroup_event *event, *tmp;
 	struct cgroup_subsys *ss;
+	LIST_HEAD(tmp_list);
 
 	lockdep_assert_held(&d->d_inode->i_mutex);
 	lockdep_assert_held(&cgroup_mutex);
@@ -4331,16 +4332,20 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
 	/*
 	 * Unregister events and notify userspace.
 	 * Notify userspace about cgroup removing only after rmdir of cgroup
-	 * directory to avoid race between userspace and kernelspace
+	 * directory to avoid race between userspace and kernelspace. Use
+	 * a temporary list to avoid a deadlock with cgroup_event_wake(). Since
+	 * cgroup_event_wake() is called with the wait queue head locked,
+	 * remove_wait_queue() cannot be called while holding event_list_lock.
 	 */
 	spin_lock(&cgrp->event_list_lock);
-	list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
+	list_splice_init(&cgrp->event_list, &tmp_list);
+	spin_unlock(&cgrp->event_list_lock);
+	list_for_each_entry_safe(event, tmp, &tmp_list, list) {
 		list_del(&event->list);
 		remove_wait_queue(event->wqh, &event->wait);
 		eventfd_signal(event->eventfd, 1);
 		schedule_work(&event->remove);
 	}
-	spin_unlock(&cgrp->event_list_lock);
 
 	return 0;
 }