Merge branch 'urgent-for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git...

Pull two RCU fixes from Paul E. McKenney:

" - Complete the work of commit dd56af42bd82 (rcu: Eliminate deadlock
    between CPU hotplug and expedited grace periods), which was
    intended to allow synchronize_sched_expedited() to be safely
    used when holding locks acquired by CPU-hotplug notifiers.
    This commit makes the put_online_cpus() avoid the deadlock
    instead of just handling the get_online_cpus().

  - Complete the work of commit 35ce7f29a44a (rcu: Create rcuo
    kthreads only for onlined CPUs), which was intended to allow
    RCU to avoid allocating unneeded kthreads on systems where the
    firmware says that there are more CPUs than are really present.
    This commit makes rcu_barrier() aware of the mismatch, so that
    it doesn't hang waiting for non-existent CPUs. "

Signed-off-by: Ingo Molnar <mingo@kernel.org>