@@ -6346,11 +6346,25 @@ static void mem_cgroup_invalidate_reclaim_iterators(struct mem_cgroup *memcg)
static void mem_cgroup_css_offline(struct cgroup *cont)
{
struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
+ struct cgroup *iter;
kmem_cgroup_css_offline(memcg);
mem_cgroup_invalidate_reclaim_iterators(memcg);
+
+ /*
+ * This requires that offlining is serialized. Right now that is
+ * guaranteed because css_killed_work_fn() holds the cgroup_mutex.
+ */
+ rcu_read_lock();
+ cgroup_for_each_descendant_post(iter, cont) {
+ rcu_read_unlock();
+ mem_cgroup_reparent_charges(mem_cgroup_from_cont(iter));
+ rcu_read_lock();
+ }
+ rcu_read_unlock();
mem_cgroup_reparent_charges(memcg);
+
mem_cgroup_destroy_all_caches(memcg);
vmpressure_cleanup(&memcg->vmpressure);
}
This is a note to let you know that I have just added a patch titled memcg: reparent charges of children before processing parent to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.11.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ------ From 67187df8235096eee29599ebc680172f1d2829e5 Mon Sep 17 00:00:00 2001 From: Filipe Brandenburger <filbranden@google.com> Date: Mon, 3 Mar 2014 15:38:25 -0800 Subject: memcg: reparent charges of children before processing parent commit 4fb1a86fb5e4209a7d4426d4e586c58e9edc74ac upstream. 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> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> [ Hugh: Yes, more differences, and the old mem_cgroup_reparent_charges line is intentionally left in for 3.10 whereas it was removed for 3.12+: that's because the css/cgroup iterator changed in between, it used not to supply the root of the subtree, but nowadays it does. ] [ luis: backported to 3.11: used Hugh's backport to 3.10 ] Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- mm/memcontrol.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) -- 1.9.1