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authorHugh Dickins <hughd@google.com>2012-03-21 16:34:21 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-03-21 17:55:01 -0700
commitca464d69b19120a826aa2534de2511a6f542edf5 (patch)
tree092582419a30825b8483640856483ea8ee56cf81
parent42aee6c495e07dba7410b863a360db6bb9ec6d66 (diff)
downloadlinux-ca464d69b19120a826aa2534de2511a6f542edf5.tar.bz2
memcg: let css_get_next() rely upon rcu_read_lock()
Remove lock and unlock around css_get_next()'s call to idr_get_next(). memcg iterators (only users of css_get_next) already did rcu_read_lock(), and its comment demands that; but add a WARN_ON_ONCE to make sure of it. Signed-off-by: Hugh Dickins <hughd@google.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Li Zefan <lizf@cn.fujitsu.com> Cc: Eric Dumazet <eric.dumazet@gmail.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--kernel/cgroup.c5
1 files changed, 2 insertions, 3 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 8eb90f25bd7b..391d5e991e5f 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -5033,6 +5033,8 @@ css_get_next(struct cgroup_subsys *ss, int id,
return NULL;
BUG_ON(!ss->use_id);
+ WARN_ON_ONCE(!rcu_read_lock_held());
+
/* fill start point for scan */
tmpid = id;
while (1) {
@@ -5040,10 +5042,7 @@ css_get_next(struct cgroup_subsys *ss, int id,
* scan next entry from bitmap(tree), tmpid is updated after
* idr_get_next().
*/
- spin_lock(&ss->id_lock);
tmp = idr_get_next(&ss->idr, &tmpid);
- spin_unlock(&ss->id_lock);
-
if (!tmp)
break;
if (tmp->depth >= depth && tmp->stack[depth] == rootid) {