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@xxxxxxxxxx>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Acked-by: Li Zefan <lizf@xxxxxxxxxxxxxx>
---
kernel/cgroup.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
--- 3.2.0+.orig/kernel/cgroup.c 2012-01-19 12:16:04.000000000 -0800
+++ 3.2.0+/kernel/cgroup.c 2012-01-19 12:22:55.188244820 -0800
@@ -5087,6 +5087,8 @@ css_get_next(struct cgroup_subsys *ss, i
return NULL;
BUG_ON(!ss->use_id);
+ WARN_ON_ONCE(!rcu_read_lock_held());
+
/* fill start point for scan */
tmpid = id;
while (1) {
@@ -5094,10 +5096,7 @@ css_get_next(struct cgroup_subsys *ss, i
* 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) {
--
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