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Subject[PATCH 2/2] mm: hugetlb: switch to css_tryget() in hugetlb_cgroup_charge_cgroup()
An exiting task might belong to an offline cgroup. In this case
an attempt to grab a cgroup reference from the task can end up
with an infinite loop in hugetlb_cgroup_charge_cgroup(), because
neither the cgroup will become online, neither the task will
be migrated to a live cgroup.

Fix this by switching over to css_tryget(). As css_tryget_online()
can't guarantee that the cgroup won't go offline, in most cases
the check doesn't make sense. In this particular case users of
hugetlb_cgroup_charge_cgroup() are not affected by this change.

A similar problem is described by commit 18fa84a2db0e ("cgroup: Use
css_tryget() instead of css_tryget_online() in task_get_css()").

Signed-off-by: Roman Gushchin <>
Cc: Tejun Heo <>
mm/hugetlb_cgroup.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
index f1930fa0b445..2ac38bdc18a1 100644
--- a/mm/hugetlb_cgroup.c
+++ b/mm/hugetlb_cgroup.c
@@ -196,7 +196,7 @@ int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,
h_cg = hugetlb_cgroup_from_task(current);
- if (!css_tryget_online(&h_cg->css)) {
+ if (!css_tryget(&h_cg->css)) {
goto again;
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