RFC Consolidate RCU dyntick-idle counter manipulation

Hello!

The first four patches of this series consolidate RCU's dyntick-idle counter manipulations into a set of access functions. These are currently queued for 4.12 (merge window after next). The last patch in this series uses the bottom bit of RCU's dyntick-idle counter to track a CPU's state, and has been proposed to track the need to flush the local CPU's TLB. This last patch will not be pushed until it has a use.

The patches are as follows:

1. Abstract the dynticks momentary-idle operation.

2. Abstract the dynticks snapshot operation.

3. Abstract dynticks extended quiescent state enter/exit operations.

4. Abstract extended quiescent state determination.

5. Maintain special bits at bottom of ->dynticks counter, which
might be used to track a given CPU's need to flush TLBs.

Thanx, Paul

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

 include/linux/rcutiny.h  |   11 +
 kernel/rcu/tree.c        |  263 ++++++++++++++++++++++++++++++++++-------------
 kernel/rcu/tree.h        |    3 
 kernel/rcu/tree_exp.h    |   12 --
 kernel/rcu/tree_plugin.h |    2 
 kernel/rcu/tree_trace.c  |    2 
 6 files changed, 216 insertions(+), 77 deletions(-)