Miscellaneous fixes for v4.18

Hello!

This series provides miscellaneous fixes:

1. Make non-production PREEMPT cond_resched() help Tasks RCU.

2. Inline rcu_preempt_do_callback() into its sole caller, courtesy
of Byungchul Park.

3. Don't allocate rcu_nocb_mask if no one needs it, for example, in
the case where there are no no-CBs CPUs.

4. Call wake_nocb_leader_defer() with 'FORCE' when nocb_q_count is
high, courtesy of Byungchul Park.

5. Remove deprecated RCU debugfs tracing code, courtesy of Byungchul
Park.

6. Rename cond_resched_rcu_qs() to cond_resched_tasks_rcu_qs() in
order to reflect its actual current use case.

7. Eliminate unused cond_resched_softirq() macro.

8. Move __rcu_read_lock() and __rcu_read_unlock() to tree_plugin.h.

9. Update rcu_bind_gp_kthread() header comment.

10. Declare rcu_eqs_special_set() in public header, courtesy of
Yury Norov.

11. Add cleanup_srcu_struct_quiesced().

12. Avoid flush dependency in delete controller flow, which is
included in this series due to its need for the shiny new cleanup_srcu_struct_quiesced() function.

13. Exclude near-simultaneous RCU CPU stall warnings.

14. Add leaf-node macros to simplify code.

15. Ensure whatisRCU.txt actually says what RCU is, courtesy of
Paul Gortmaker.

16-21: Debugging commits that may or may not be submitted for inclusion,
depending on how helpful they prove to be.

22: Use the proper lockdep annotation in dump_blkd_tasks(),
courtesy of Boqun Feng.

Thanx, Paul

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

 Documentation/RCU/whatisRCU.txt |    2 
 drivers/nvme/host/core.c        |    2 
 include/linux/rcupdate.h        |    4 -
 include/linux/rcutree.h         |    1 
 include/linux/sched.h           |   14 ++--
 include/linux/srcu.h            |   36 ++++++++++++
 kernel/rcu/rcu.h                |   11 ++-
 kernel/rcu/rcuperf.c            |    2 
 kernel/rcu/rcutorture.c         |    7 ++
 kernel/rcu/srcutiny.c           |    9 ++-
 kernel/rcu/srcutree.c           |   30 +++++-----
 kernel/rcu/tree.c               |   76 ++++++++++++++------------
 kernel/rcu/tree.h               |    8 --
 kernel/rcu/tree_exp.h           |   13 +---
 kernel/rcu/tree_plugin.h        |  116 +++++++++++++++++++++++++++++++---------
 kernel/rcu/update.c             |   50 -----------------
 kernel/sched/core.c             |   14 ----
 kernel/softirq.c                |    3 -
 kernel/torture.c                |    2 
 kernel/trace/trace_benchmark.c  |    4 -
 20 files changed, 232 insertions(+), 172 deletions(-)