[lkml]   [2019]   [Dec]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH 3.16 131/136] mm: hugetlb: switch to css_tryget() in hugetlb_cgroup_charge_cgroup()
3.16.80-rc1 review patch.  If anyone has any objections, please let me know.


From: Roman Gushchin <>

commit 0362f326d86c645b5e96b7dbc3ee515986ed019d upstream.

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

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 <>
Acked-by: Johannes Weiner <>
Acked-by: Tejun Heo <>
Reviewed-by: Shakeel Butt <>
Cc: Michal Hocko <>
Signed-off-by: Andrew Morton <>
Signed-off-by: Linus Torvalds <>
Signed-off-by: Ben Hutchings <>
mm/hugetlb_cgroup.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/hugetlb_cgroup.c
+++ b/mm/hugetlb_cgroup.c
@@ -181,7 +181,7 @@ int hugetlb_cgroup_charge_cgroup(int idx
h_cg = hugetlb_cgroup_from_task(current);
- if (!css_tryget_online(&h_cg->css)) {
+ if (!css_tryget(&h_cg->css)) {
goto again;
 \ /
  Last update: 2019-12-17 01:54    [W:0.241 / U:1.020 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site