[PATCH tip/core/rcu 0/2] Enforce RCU grace-period transitivity

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

Hello!

Within RCU, acquisitions of the rcu_node structure's ->lock field must
be followed by smp_mb__after_unlock_lock() in order to enforce RCU's
grace-period memory-ordering guarantees.  In theory, acquisitions for
debug purposes need not have smp_mb__after_unlock_lock(), but in practice,
anything other than fully consistent enforcement of this rule is a recipe
for disaster.  This series therefore adds smp_mb__after_unlock_lock()
for consistency:

1.	Create wrapper functions to minimize the number of these
	smp_mb__after_unlock_lock() calls, and apply these wrapper
	functions throughout.  Courtesy of Peter Zijlstra.

2.	Catch up wrapper-function application to patches that were
	in flight at the time #1 was created.

							Thanx, Paul

------------------------------------------------------------------------

 b/kernel/rcu/tree.c        |  102 ++++++++++++++++-----------------------------
 b/kernel/rcu/tree.h        |   39 +++++++++++++++++
 b/kernel/rcu/tree_plugin.h |   20 +++-----
 b/kernel/rcu/tree_trace.c  |    2 
 4 files changed, 85 insertions(+), 78 deletions(-)