Message-ID: <4C805293.1020305@cn.fujitsu.com>
Date: Fri, 03 Sep 2010 09:42:43 +0800
From: Li Zefan <lizf@cn.fujitsu.com>
To: David Miller <davem@davemloft.net>
CC: Herbert Xu <herbert@gondor.hengli.com.au>, Dave Jones <davej@redhat.com>,
netdev <netdev@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>, Paul Menage <menage@google.com>
Subject: [PATCH v2] cls_cgroup: Fix rcu lockdep warning
Dave reported an rcu lockdep warning on 2.6.35.4 kernel
task->cgroups and task->cgroups->subsys[i] are protected by RCU.
So we avoid accessing invalid pointers here. This might happen,
for example, when you are deref-ing those pointers while someone
move @task from one cgroup to another.
Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
include/net/cls_cgroup.h | 10 ++++++++--
1 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/include/net/cls_cgroup.h b/include/net/cls_cgroup.h
index dd1fdb8..a4dc5b0 100644
--- a/include/net/cls_cgroup.h
+++ b/include/net/cls_cgroup.h
@@ -27,11 +27,17 @@ struct cgroup_cls_state
#ifdef CONFIG_NET_CLS_CGROUP
static inline u32 task_cls_classid(struct task_struct *p)
{
+ int classid;
+
if (in_interrupt())
return 0;
- return container_of(task_subsys_state(p, net_cls_subsys_id),
- struct cgroup_cls_state, css)->classid;
+ rcu_read_lock();
+ classid = container_of(task_subsys_state(p, net_cls_subsys_id),
+ struct cgroup_cls_state, css)->classid;
+ rcu_read_unlock();
+
+ return classid;
}
#else
extern int net_cls_subsys_id;