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authorKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>2010-05-11 14:06:59 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-05-11 17:33:42 -0700
commit747388d78a0ae768fd82b55c4ed38aa646a72364 (patch)
tree03efabf9761209cffef4e8da9b6989887f76428e /mm/memcontrol.c
parent7f0f15464185a92f9d8791ad231bcd7bf6df54e4 (diff)
downloadvexpress-lsk-747388d78a0ae768fd82b55c4ed38aa646a72364.tar.gz
memcg: fix css_is_ancestor() RCU locking
Some callers (in memcontrol.c) calls css_is_ancestor() without rcu_read_lock. Because css_is_ancestor() has to access RCU protected data, it should be under rcu_read_lock(). This makes css_is_ancestor() itself does safe access to RCU protected area. (At least, "root" can have refcnt==0 if it's not an ancestor of "child". So, we need rcu_read_lock().) Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> 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>
Diffstat (limited to 'mm/memcontrol.c')
-rw-r--r--mm/memcontrol.c4
1 files changed, 0 insertions, 4 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 595d03f33b2..8a79a6f0f02 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -811,12 +811,10 @@ int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)
* enabled in "curr" and "curr" is a child of "mem" in *cgroup*
* hierarchy(even if use_hierarchy is disabled in "mem").
*/
- rcu_read_lock();
if (mem->use_hierarchy)
ret = css_is_ancestor(&curr->css, &mem->css);
else
ret = (curr == mem);
- rcu_read_unlock();
css_put(&curr->css);
return ret;
}
@@ -1603,7 +1601,6 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
* There is a small race that "from" or "to" can be
* freed by rmdir, so we use css_tryget().
*/
- rcu_read_lock();
from = mc.from;
to = mc.to;
if (from && css_tryget(&from->css)) {
@@ -1624,7 +1621,6 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
do_continue = (to == mem_over_limit);
css_put(&to->css);
}
- rcu_read_unlock();
if (do_continue) {
DEFINE_WAIT(wait);
prepare_to_wait(&mc.waitq, &wait,