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    Subject[PATCH v2.6.34-rc5 02/12] rcu: fix RCU lockdep splat on freezer_fork path
    Date
    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>
    ---
    kernel/cgroup_freezer.c | 5 ++++-
    1 files changed, 4 insertions(+), 1 deletions(-)

    diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
    index da5e139..e5c0244 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
    --
    1.7.0


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