Pull RCU fixes from Thomas Gleixner:
 "Two RCU patches:
   - Address a serious performance regression on open/close caused by
     commit ac1bea85 ("Make cond_resched() report RCU quiescent
     states")
   - Export RCU debug functions.  Not a regression, but enablement to
     address a serious recursion bug in the sl*b allocators in 3.17"

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  rcu: Reduce overhead of cond_resched() checks for RCU
  rcu: Export debug_init_rcu_head() and and debug_init_rcu_head()