Commit 3fb5a991 authored Sep 02, 2010 by Li Zefan Committed by David S. Miller Sep 03, 2010

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>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 323f30b3

include/net/cls_cgroup.h

+8 −2

Original line number	Diff line number	Diff line
		@@ -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),
		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;

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