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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-04-21 13:02:08 -0700
committerIngo Molnar <mingo@elte.hu>2010-04-30 12:03:17 +0200
commit8b46f880841aac821af8efa6581bb0e46b8b9845 (patch)
tree4172415abf0f8cbbdd7367023cf521e7a56b9a3a /kernel/cgroup_freezer.c
parent8b08ca52f5942c21564bbb90ccfb61053f2c26a1 (diff)
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rcu: Fix RCU lockdep splat on freezer_fork path
Add an RCU read-side critical section to suppress this false positive. Located-by: Eric Paris <eparis@parisplace.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Li Zefan <lizf@cn.fujitsu.com> Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com Cc: eric.dumazet@gmail.com LKML-Reference: <1271880131-3951-2-git-send-email-paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/cgroup_freezer.c')
-rw-r--r--kernel/cgroup_freezer.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index da5e1397553..e5c0244962b 100644
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -205,9 +205,12 @@ static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task)
* No lock is needed, since the task isn't on tasklist yet,
* so it can't be moved to another cgroup, which means the
* freezer won't be removed and will be valid during this
- * function call.
+ * function call. Nevertheless, apply RCU read-side critical
+ * section to suppress RCU lockdep false positives.
*/
+ rcu_read_lock();
freezer = task_freezer(task);
+ rcu_read_unlock();
/*
* The root cgroup is non-freezable, so we can skip the