lkml.org 
[lkml]   [2019]   [Nov]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 2/2] mm: hugetlb: switch to css_tryget() in hugetlb_cgroup_charge_cgroup()
Date
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 <guro@fb.com>
Cc: stable@vger.kernel.org
Cc: Tejun Heo <tj@kernel.org>
---
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,
again:
rcu_read_lock();
h_cg = hugetlb_cgroup_from_task(current);
- if (!css_tryget_online(&h_cg->css)) {
+ if (!css_tryget(&h_cg->css)) {
rcu_read_unlock();
goto again;
}
--
2.17.1
\
 
 \ /
  Last update: 2019-11-06 23:53    [W:0.334 / U:0.176 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site