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Commit 20b454a6 authored by Tejun Heo's avatar Tejun Heo
Browse files

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: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarZefan Li <lizefan@huawei.com>
parent 2378d8b8

kernel/cgroup.c

+3 −2
Original line number Diff line number Diff line
@@ -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);