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authorFilipe Brandenburger <filbranden@google.com>2014-03-03 18:38:25 -0500
committerLinus Torvalds <torvalds@linux-foundation.org>2014-03-04 10:55:48 -0500
commit4fb1a86fb5e4209a7d4426d4e586c58e9edc74ac (patch)
tree3afeae40bb074a8670a83babc1ce76cf8def31fa /mm/memcontrol.c
parentce48225fe3b1b0d1fc9fceb96ac3d8a879e45114 (diff)
memcg: reparent charges of children before processing parent
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(). Further testing showed that an ordered workqueue for cgroup_destroy_wq is not always good enough: percpu_ref_kill_and_confirm's call_rcu_sched stage on the way can mess up the order before reaching the workqueue. Instead, when offlining a memcg, call mem_cgroup_reparent_charges() on all its children (and grandchildren, in the correct order) to have their charges reparented first. Fixes: e5fca243abae ("cgroup: use a dedicated workqueue for cgroup destruction") Signed-off-by: Filipe Brandenburger <filbranden@google.com> Signed-off-by: Hugh Dickins <hughd@google.com> Reviewed-by: Tejun Heo <tj@kernel.org> Acked-by: Michal Hocko <mhocko@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: <stable@vger.kernel.org> [v3.10+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memcontrol.c')
-rw-r--r--mm/memcontrol.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 9d17310be470..5b6b0039f725 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6595,6 +6595,7 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
6595{ 6595{
6596 struct mem_cgroup *memcg = mem_cgroup_from_css(css); 6596 struct mem_cgroup *memcg = mem_cgroup_from_css(css);
6597 struct mem_cgroup_event *event, *tmp; 6597 struct mem_cgroup_event *event, *tmp;
6598 struct cgroup_subsys_state *iter;
6598 6599
6599 /* 6600 /*
6600 * Unregister events and notify userspace. 6601 * Unregister events and notify userspace.
@@ -6611,7 +6612,14 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
6611 kmem_cgroup_css_offline(memcg); 6612 kmem_cgroup_css_offline(memcg);
6612 6613
6613 mem_cgroup_invalidate_reclaim_iterators(memcg); 6614 mem_cgroup_invalidate_reclaim_iterators(memcg);
6614 mem_cgroup_reparent_charges(memcg); 6615
6616 /*
6617 * This requires that offlining is serialized. Right now that is
6618 * guaranteed because css_killed_work_fn() holds the cgroup_mutex.
6619 */
6620 css_for_each_descendant_post(iter, css)
6621 mem_cgroup_reparent_charges(mem_cgroup_from_css(iter));
6622
6615 mem_cgroup_destroy_all_caches(memcg); 6623 mem_cgroup_destroy_all_caches(memcg);
6616 vmpressure_cleanup(&memcg->vmpressure); 6624 vmpressure_cleanup(&memcg->vmpressure);
6617} 6625}