From 20b454a61fba59be13de52b4493898583ea26d20 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 3 Mar 2016 09:57:57 -0500 Subject: [PATCH] cgroup: suppress spurious de-populated events During task migration, tasks may transfer between two css_sets which are associated with the same cgroup. If those tasks are the only tasks in the cgroup, this currently triggers a spurious de-populated event on the cgroup. Fix it by bumping up populated count before bumping it down during migration to ensure that it doesn't reach zero spuriously. Signed-off-by: Tejun Heo Acked-by: Zefan Li --- kernel/cgroup.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index e97772b..5d452e7 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -678,6 +678,9 @@ static void css_set_move_task(struct task_struct *task, { lockdep_assert_held(&css_set_lock); + if (to_cset && !css_set_populated(to_cset)) + css_set_update_populated(to_cset, true); + if (from_cset) { struct css_task_iter *it, *pos; @@ -711,8 +714,6 @@ static void css_set_move_task(struct task_struct *task, */ WARN_ON_ONCE(task->flags & PF_EXITING); - if (!css_set_populated(to_cset)) - css_set_update_populated(to_cset, true); rcu_assign_pointer(task->cgroups, to_cset); list_add_tail(&task->cg_list, use_mg_tasks ? &to_cset->mg_tasks : &to_cset->tasks); -- 2.7.4