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 <tj@xxxxxxxxxx>
---
kernel/cgroup.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -678,6 +678,9 @@ static void css_set_move_task(struct tas
{
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 tas
*/
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);
--
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