[PATCH tip/core/rcu 0/19] Expedited grace period changes for 4.3

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

Hello!

This series contains a series of optimizations for RCU's expedited
grace periods that reduce the jitter they induce in other CPUs.  There
is more work to be done here, but this should introduce a good and
sufficient level of instability for 4.3.  :-/

1.	Stop disabling CPU hotplug in synchronize_rcu_expedited().
	Longer term, synchronize_sched_expedited() will get the
	same treatment.

2.	Remove CONFIG_RCU_CPU_STALL_INFO, so that kernels are always
	built as if CONFIG_RCU_CPU_STALL_INFO=y.  A bit off-topic,
	but remains in this series due to conflicts.

3.	Switch synchronize_sched_expedited() to stop_one_cpu(), courtesy
	of Peter Zijlstra.

4.	Simplify synchronize_sched_expedited() counter handling.

5.	Get rid of synchronize_sched_expedited()'s polling loop in
	favor of tree-based funnel locking.

6.	Make expedited GP CPU stoppage asynchronous, courtesy of Peter
	Zijlstra.  This repairs a performance regression in #3.

7.	Abstract sequence counting from synchronize_sched_expedited().

8.	Make synchronize_rcu_expedited() use sequence-counter scheme.

9.	Abstract funnel locking from synchronize_sched_expedited().

10.	Fix synchronize_sched_expedited() type error for variable "s".

11.	Use funnel locking for synchronize_rcu_expedited()'s polling loop.

12.	Apply rcu_seq operations to _rcu_barrier().

13.	Consolidate last open-coded expedited memory barrier.

14.	Extend expedited funnel locking to rcu_data structure, allowing
	full parallel handling of expedited grace periods.

15.	Add stall warnings to synchronize_sched_expedited().

16.	Document new expedited stall warnings.

17.	Pull out wait_event*() condition into helper function.

18.	Rename RCU_GP_DONE_FQS to RCU_GP_DOING_FQS.

19.	Add fastpath bypassing funnel locking to speed up the common
	case where only one expedited grace period happens at a time
	across the full system.

							Thanx, Paul

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

 b/Documentation/RCU/stallwarn.txt                             |   29 
 b/Documentation/RCU/trace.txt                                 |   36 
 b/include/trace/events/rcu.h                                  |    1 
 b/kernel/rcu/tree.c                                           |  625 +++++-----
 b/kernel/rcu/tree.h                                           |   39 
 b/kernel/rcu/tree_plugin.h                                    |  123 -
 b/kernel/rcu/tree_trace.c                                     |   29 
 b/lib/Kconfig.debug                                           |   14 
 b/tools/testing/selftests/rcutorture/configs/rcu/TREE01       |    1 
 b/tools/testing/selftests/rcutorture/configs/rcu/TREE02       |    1 
 b/tools/testing/selftests/rcutorture/configs/rcu/TREE02-T     |    1 
 b/tools/testing/selftests/rcutorture/configs/rcu/TREE03       |    1 
 b/tools/testing/selftests/rcutorture/configs/rcu/TREE04       |    1 
 b/tools/testing/selftests/rcutorture/configs/rcu/TREE05       |    1 
 b/tools/testing/selftests/rcutorture/configs/rcu/TREE06       |    1 
 b/tools/testing/selftests/rcutorture/configs/rcu/TREE07       |    1 
 b/tools/testing/selftests/rcutorture/configs/rcu/TREE08       |    1 
 b/tools/testing/selftests/rcutorture/configs/rcu/TREE08-T     |    1 
 b/tools/testing/selftests/rcutorture/configs/rcu/TREE09       |    1 
 b/tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt |    1 
 20 files changed, 425 insertions(+), 483 deletions(-)