[PATCH v2 0/21] Add atomic SRCU &c for v7.4

[Paul E. McKenney]

Hello!

This series adds an atomic SRCU and some additional adjustments:

1.	Make a Tiny SRCU grace period imply an RCU grace period.

2.	Suppress srcu_advance_state() mutex_lock in atomic.

3.	Suppress to-big transition for atomic SRCU.

4.	Add an atomic Tree SRCU.

5.	Add an atomic Tiny SRCU.

6.	Add support for testing synchronize_srcu_atomic().

7.	Disable preemption across synchronize_srcu_atomic().

8.	Use IRQ_WORK_INIT_HARD for srcu's irq_work, courtesy of Sebastian
	Andrzej Siewior.

9.	Warn if Tiny SRCU readers are preempted.

10.	Explicitly note DEFINE_SRCU() needs for srcu_barrier().

11.	Add atomic-SRCU support to torture.sh, courtesy of Kunwu Chan.

12.	Add reader-free fastpath to synchronize_srcu_atomic(), courtesy
	of Kunwu Chan.

13.	Skip callback scheduling for atomic SRCU grace periods, courtesy
	of Kunwu Chan.

14.	Remove srcu_barrier() sleep for atomic SRCU, courtesy of Kunwu
	Chan.

15.	Restrict atomic-SRCU non_block annotation to task context,
	courtesy of Kunwu Chan.

16.	Make init_srcu_struct_atomic() prevent transition to big,
	courtesy of Kunwu Chan.

17.	Don't transition atomic SRCU to big in srcu_gp_end(), courtesy
	of Kunwu Chan.

18.	Skip torture to-big transition for atomic SRCU, courtesy of
	Kunwu Chan.

19.	Add lockdep and early-boot checks to synchronize_srcu_atomic(),
	courtesy of Kunwu Chan.

20.	Add lockdep and early-boot checks to synchronize_srcu_atomic(),
	courtesy of Kunwu Chan.

21.	Preserve IRQ state in synchronize_srcu_atomic() callchain,
	courtesy of Kunwu Chan.

Changes since v1:
https://lore.kernel.org/all/13d6be93-8d9d-47a2-beb0-99c8a90938d4@paulmck-laptop/

o	Added patches 19-21.

o	Dropped old patch 9 in favor of an urgent RFC pull request.

						Thanx, Paul

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

 b/include/linux/srcu.h                              |   81 ++++
 b/include/linux/srcutiny.h                          |    6 
 b/include/linux/srcutree.h                          |    9 
 b/kernel/rcu/rcutorture.c                           |   46 ++
 b/kernel/rcu/srcutiny.c                             |    2 
 b/kernel/rcu/srcutree.c                             |   23 -
 b/tools/testing/selftests/rcutorture/bin/torture.sh |   24 +
 include/linux/srcu.h                                |   10 
 include/linux/srcutree.h                            |    6 
 kernel/rcu/srcutiny.c                               |   94 +++++
 kernel/rcu/srcutree.c                               |  333 ++++++++++++++++----
 11 files changed, 548 insertions(+), 86 deletions(-)