Documentation updates for v4.21/v5.0

Hello!

This series provides documentation updates:

1. Set down forward-progress requirements.

2. Clarify RCU data-structure comment about rcu_tree fanout,
courtesy of Joel Fernandes.

3. Remove rcu_preempt_state reference in stallwarn, courtesy of
Joel Fernandes.

4. Update information about resched_cpu, courtesy of Joel Fernandes.

5. Remove rcu_dynticks from Data-Structures, courtesy of Joel
Fernandes.

6. Update Data-Structures for RCU flavor consolidation, courtesy of
Joel Fernandes.

7. Better clarify the rcu_segcblist ->len field, courtesy of Joel
Fernandes.

8. Update description of gp_seq fields in rcu_data, courtesy of
Joel Fernandes.

9. Document rcutorture forward-progress test kernel parameters.

10. Update core and full API in whatisRCU, courtesy of Joel Fernandes.

11. Add more rationale for using rcu_read_lock_sched() in checklist,
courtesy of Joel Fernandes.

12. Remove obsolete suggestion from checklist, courtesy of Joel
Fernandes.

13. Remove obsolete checklist item about synchronize_rcu() usage,
courtesy of Joel Fernandes.

14. Encourage use of rcu_barrier in checklist, courtesy of Joel
Fernandes.

15. Make reader aware of rcu_dereference_protected(), courtesy of
Joel Fernandes.

16. Remove obsolete (non-)requirement about disabling preemption,
courtesy of Joel Fernandes.

17. Make listing in RCU perf/scale requirements use rcu_assign_pointer(),
courtesy of Joel Fernandes.

18. RCU scheduler spinlock rcu_read_unlock() restriction remains.

19. Correct the parameter in stallwarn, courtesy of Joel Fernandes.

20. Fix "struction" typo in RCU memory-ordering documentation,
courtesy of Joel Fernandes.

Thanx, Paul

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 Documentation/RCU/Design/Data-Structures/BigTreeClassicRCUBH.svg                |  499 -----
 Documentation/RCU/Design/Data-Structures/BigTreeClassicRCUBHdyntick.svg         |  695 --------
 Documentation/RCU/Design/Data-Structures/BigTreePreemptRCUBHdyntick.svg         |  741 --------
 b/Documentation/RCU/Design/Data-Structures/BigTreePreemptRCUBHdyntickCB.svg     |  834 +++-------
 b/Documentation/RCU/Design/Data-Structures/Data-Structures.html                 |  177 --
 b/Documentation/RCU/Design/Data-Structures/blkd_task.svg                        |  676 ++------
 b/Documentation/RCU/Design/Expedited-Grace-Periods/Expedited-Grace-Periods.html |    6 
 b/Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.html        |    2 
 b/Documentation/RCU/Design/Requirements/Requirements.html                       |  206 +-
 b/Documentation/RCU/checklist.txt                                               |   49 
 b/Documentation/RCU/stallwarn.txt                                               |    7 
 b/Documentation/RCU/whatisRCU.txt                                               |   70 
 b/Documentation/admin-guide/kernel-parameters.txt                               |   17 
 13 files changed, 823 insertions(+), 3156 deletions(-)