diff options
| author | Greg Thelen <gthelen@google.com> | 2012-11-28 13:50:44 -0800 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2012-11-28 13:51:56 -0800 |
| commit | 205a872bd6f9a9a09ef035ef1e90185a8245cc58 (patch) | |
| tree | 9b39a5823dddf6319a021d4ab36c7cd35f612908 /kernel/cgroup.c | |
| parent | fddfb02ad0d0d3b479c2a26a8ae7e6411b34706b (diff) | |
cgroup: fix lockdep warning for event_control
The cgroup_event_wake() function is called with the wait queue head
locked and it takes cgrp->event_list_lock. However, in cgroup_rmdir()
remove_wait_queue() was being called after taking
cgrp->event_list_lock. Correct the lock ordering by using a temporary
list to obtain the event list to remove from the wait queue.
Signed-off-by: Greg Thelen <gthelen@google.com>
Signed-off-by: Aaron Durbin <adurbin@google.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel/cgroup.c')
| -rw-r--r-- | kernel/cgroup.c | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index c02b05560d1..589433f7a74 100644 --- a/kernel/cgroup.c +++ b/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; } |