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cls_cgroup: Fix rcu lockdep warning

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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>
This commit is contained in:
Li Zefan 2010-09-02 15:42:43 +00:00 committed by David S. Miller
parent 323f30b361
commit 3fb5a99191
1 changed files with 8 additions and 2 deletions
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10
include/net/cls_cgroup.h
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@ -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;