Merge branch 'rcu/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck...

Pull RCU updates from Paul E. McKenney:

 "This series greatly reduces the performance degradation of Tree SRCU
  on a CPU-hotplug stress test.  The effect was not subtle:  Mike Galbraith
  measured Classic SRCU at 55 seconds and Tree SRCU at more than 16 -minutes-
  for this test.  Mike collected ftrace data that showed that Classic SRCU
  was auto-expediting invocations of synchronize_srcu() that found SRCU
  completely idle.  This series therefore adds this auto-expedite capability
  to Tree SRCU, bringing the performance shortfall to less than ten seconds,
  which is a great improvement over the initial shortfall of 15 minutes."

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