Hello, Greg.
On Wed, Nov 28, 2012 at 12:15:42PM -0800, Greg Thelen wrote:
> @@ -4276,6 +4276,7 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
> DEFINE_WAIT(wait);
> struct cgroup_event *event, *tmp;
> struct cgroup_subsys *ss;
> + struct list_head tmp_list;
LIST_HEAD(tmp_list);
>
> lockdep_assert_held(&d->d_inode->i_mutex);
> lockdep_assert_held(&cgroup_mutex);
> @@ -4330,16 +4331,20 @@ 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_replace_init(&cgrp->event_list, &tmp_list);
list_splice_init();
would be more conventional, I think.
> + spin_unlock(&cgrp->event_list_lock);
> + list_for_each_entry_safe(event, tmp, &tmp_list, list) {
> list_del(&event->list);
Maybe convert this to list_del_init() while at it?
> remove_wait_queue(event->wqh, &event->wait);
> eventfd_signal(event->eventfd, 1);
> schedule_work(&event->remove);
> }
> - spin_unlock(&cgrp->event_list_lock);
Thanks.
--
tejun
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