leandrof/linux
1
0
Fork 0
forked from Minki/linux
Code Issues Pull Requests Packages Projects Releases Wiki Activity

cgroup: use an ordered workqueue for cgroup destruction

Browse Source 
Sometimes the cleanup after memcg hierarchy testing gets stuck in
mem_cgroup_reparent_charges(), unable to bring non-kmem usage down to 0.

There may turn out to be several causes, but a major cause is this: the
workitem to offline parent can get run before workitem to offline child;
parent's mem_cgroup_reparent_charges() circles around waiting for the
child's pages to be reparented to its lrus, but it's holding cgroup_mutex
which prevents the child from reaching its mem_cgroup_reparent_charges().

Just use an ordered workqueue for cgroup_destroy_wq.

tj: Committing as the temporary fix until the reverse dependency can
    be removed from memcg.  Comment updated accordingly.

Fixes: e5fca243ab ("cgroup: use a dedicated workqueue for cgroup destruction")
Suggested-by: Filipe Brandenburger <filbranden@google.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: stable@vger.kernel.org # 3.10+
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Hugh Dickins 2014-02-06 15:56:01 -08:00 committed by Tejun Heo
parent 0a6be65553
commit ab3f5faa62
1 changed files with 6 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
kernel/cgroup.c
View File

@ -4845,12 +4845,16 @@ static int __init cgroup_wq_init(void)
/*
* There isn't much point in executing destruction path in
* parallel. Good chunk is serialized with cgroup_mutex anyway.
* Use 1 for @max_active.
*
* XXX: Must be ordered to make sure parent is offlined after
* children. The ordering requirement is for memcg where a
* parent's offline may wait for a child's leading to deadlock. In
* the long term, this should be fixed from memcg side.
*
* We would prefer to do this in cgroup_init() above, but that
* is called before init_workqueues(): so leave this until after.
*/
cgroup_destroy_wq = alloc_workqueue("cgroup_destroy", 0, 1);
cgroup_destroy_wq = alloc_ordered_workqueue("cgroup_destroy", 0);
BUG_ON(!cgroup_destroy_wq);
/*