Tree geometry-initialization simplifications for 4.3

Hello!

This series simplifies the arithmetic involved in computing the geometry of Tree RCU's combining tree.

1. Provide more diagnostics for stalled GP kthread. (A bit off-topic,
but included in this series due to conflicting updates.)

2. Panic if RCU tree can not accommodate all CPUs, courtesy of
Alexander Gordeev.

3. Remove superfluous local variable in rcu_init_geometry(),
courtesy of Alexander Gordeev.

4. Cleanup rcu_init_geometry() code and arithmetic, courtesy of
Alexander Gordeev.

5. Simplify rcu_init_geometry() capacity arithmetic, courtesy of
Alexander Gordeev.

6. Limit rcu_state::levelcnt[] to RCU_NUM_LVLS items, courtesy of
Alexander Gordeev.

7. Limit rcu_capacity[] size to RCU_NUM_LVLS items, courtesy of
Alexander Gordeev.

8. Remove unnecessary fields from rcu_state structure, courtesy of
Alexander Gordeev.

9. Limit count of static data to the number of RCU levels, courtesy
of Alexander Gordeev.

10. Simplify arithmetic to calculate number of RCU nodes, courtesy
of Alexander Gordeev.

11. Shut up bogus gcc array bounds warning, courtesy of Alexander
Gordeev.

12. Reset rcu_fanout_leaf if out of bounds.

Thanx, Paul

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

 b/kernel/rcu/tree.c        |  156 +++++++++++++++++++++------------------------
 b/kernel/rcu/tree.h        |   45 +++++++-----
 b/kernel/rcu/tree_plugin.h |    4 -
 3 files changed, 103 insertions(+), 102 deletions(-)