cgroup: use read lock to guard find_existing_css_set()
The function does not modify anything (except the temporary css template), so
it's sufficient to hold read lock.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Paul Menage <menage@google.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 15ac0e1..f50edad 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -415,11 +415,11 @@
/* First see if we already have a cgroup group that matches
* the desired set */
- write_lock(&css_set_lock);
+ read_lock(&css_set_lock);
res = find_existing_css_set(oldcg, cgrp, template);
if (res)
get_css_set(res);
- write_unlock(&css_set_lock);
+ read_unlock(&css_set_lock);
if (res)
return res;