cgroup: Check task_lock in task_subsys_state()
authorLi Zefan <lizf@cn.fujitsu.com>
Fri, 23 Apr 2010 02:35:52 +0000 (10:35 +0800)
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Tue, 4 May 2010 16:25:02 +0000 (09:25 -0700)
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>
include/linux/cgroup.h

index b8ad1ea..8f78073 100644 (file)
@@ -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());
 }