[PATCH tip/core/rcu 0/3] increase rcutorture intensity and fix a couple resulting bugs

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

This patch series increases the intensity of rcutorture testing for
TREE_PREEMPT_RCU and provides fixes for a couple resulting bugs.

o	Make rcutorture's RCU read-side critical sections occasionally
	spin for a few tens of milliseconds, which greatly increases
	the probability that they will be preempted and that quiescent
	states will be forced.  Yes, this does uncover some bugs in
	TREE_PREEMPT_RCU (though TREE_RCU passes with flying colors).

o	Fix a bug where rnp->gpnum was not being updated.  This
	increases TREE_PREEMPT_RCU's reliability considerably, though
	bugs still remain.

o	Make the initialization of multi-node trees of rcu_node
	structures unconditionally acquire rnp->lock.  This simplifies
	the code a bit and will make it easier to allow grace-period
	initialization become preemptable, should this be needed.

Next steps include applying review comments, adding expedited grace
periods, and chasing down remaining bugs.  Longer term, RCU priority
boosting.

 b/kernel/rcutorture.c |   16 +++++++++-------
 b/kernel/rcutree.c    |    7 +++++--
 kernel/rcutree.c      |   42 ++++++++++++------------------------------
 3 files changed, 26 insertions(+), 39 deletions(-)