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authorTejun Heo <tj@kernel.org>2015-10-15 16:41:50 -0400
committerTejun Heo <tj@kernel.org>2015-10-15 16:41:50 -0400
commit27bd4dbb8d51c476298e62bd088225317b7853de (patch)
treeb61ec19505113cef0053780c403945266b24589e /mm/memcontrol.c
parent0de0942db2b36dd91c088a7950398d2e87f23b23 (diff)
cgroup: replace cgroup_has_tasks() with cgroup_is_populated()
Currently, cgroup_has_tasks() tests whether the target cgroup has any css_set linked to it. This works because a css_set's refcnt converges with the number of tasks linked to it and thus there's no css_set linked to a cgroup if it doesn't have any live tasks. To help tracking resource usage of zombie tasks, putting the ref of css_set will be separated from disassociating the task from the css_set which means that a cgroup may have css_sets linked to it even when it doesn't have any live tasks. This patch replaces cgroup_has_tasks() with cgroup_is_populated() which tests cgroup->nr_populated instead which locally counts the number of populated css_sets. Unlike cgroup_has_tasks(), cgroup_is_populated() is recursive - if any of the descendants is populated, the cgroup is populated too. While this changes the meaning of the test, all the existing users are okay with the change. While at it, replace the open-coded ->populated_cnt test in cgroup_events_show() with cgroup_is_populated(). Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Li Zefan <lizefan@huawei.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org>
Diffstat (limited to 'mm/memcontrol.c')
-rw-r--r--mm/memcontrol.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 33c8dad6830f..0ddd0ff2b52e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2920,7 +2920,7 @@ static int memcg_activate_kmem(struct mem_cgroup *memcg,
* of course permitted.
*/
mutex_lock(&memcg_create_mutex);
- if (cgroup_has_tasks(memcg->css.cgroup) ||
+ if (cgroup_is_populated(memcg->css.cgroup) ||
(memcg->use_hierarchy && memcg_has_children(memcg)))
err = -EBUSY;
mutex_unlock(&memcg_create_mutex);