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cgroup: catch bad css refcnt at css_put

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__css_put() doesn't check a bug as refcnt goes to minus.
I think it should be caught. This patch adds a check for it.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
KAMEZAWA Hiroyuki 2009-10-01 15:44:09 -07:00 committed by Linus Torvalds
parent 26251eaf98
commit 3dece8347d
1 changed files with 4 additions and 1 deletions
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5
kernel/cgroup.c
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@ -3708,8 +3708,10 @@ static void check_for_release(struct cgroup *cgrp)
void __css_put(struct cgroup_subsys_state *css)
{
struct cgroup *cgrp = css->cgroup;
int val;
rcu_read_lock();
if (atomic_dec_return(&css->refcnt) == 1) {
val = atomic_dec_return(&css->refcnt);
if (val == 1) {
if (notify_on_release(cgrp)) {
set_bit(CGRP_RELEASABLE, &cgrp->flags);
check_for_release(cgrp);
@ -3717,6 +3719,7 @@ void __css_put(struct cgroup_subsys_state *css)
cgroup_wakeup_rmdir_waiter(cgrp);
}
rcu_read_unlock();
WARN_ON_ONCE(val < 1);
}
/*