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cgroup: Check task_lock in task_subsys_state()

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Expand task_subsys_state()'s rcu_dereference_check() to include the full
locking rule as documented in Documentation/cgroups/cgroups.txt by adding
a check for task->alloc_lock being held.

This fixes an RCU false positive when resuming from suspend. The warning
comes from freezer cgroup in cgroup_freezing_or_frozen().

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Matt Helsley <matthltc@us.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Li Zefan 2010-04-23 10:35:52 +08:00 committed by Paul E. McKenney
parent b629317e66
commit 1ce7e4ff24
1 changed files with 1 additions and 0 deletions
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include/linux/cgroup.h
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@ -530,6 +530,7 @@ static inline struct cgroup_subsys_state *task_subsys_state(
{
return rcu_dereference_check(task->cgroups->subsys[subsys_id],
rcu_read_lock_held() ||
lockdep_is_held(&task->alloc_lock) ||
cgroup_lock_is_held());
}