Array-based RCU removals for 4.2

Hello!

This series removes the sole use of RCU-protected array indexes. It turns out that this use is in x86 code, so smp_load_acquire() works just as well, and this allows removing a troublesome aspect of the RCU API. This removal should in turn allow compilers to better grok RCU dependency chains. For example, expressions like (x-x), (x*0), and (x%1) can result in valid array indexes, but cannot produce valid pointers.

1. Make x86's MCE code use smp_load_acuire() and READ_ONCE() in
place of the RCU API members intended to handle RCU-protected array indexes.

2. Eliminates the RCU API members supporting RCU-protected array
indexes, namely rcu_access_index() and rcu_dereference_index_check().

3. Updates the RCU documentation to reflect #2 above.

4. Makes one of the modified functions be static, courtesy of
Fengguang Wu.

Thanx, Paul

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

 b/Documentation/RCU/arrayRCU.txt        |   20 ++++++++++--
 b/Documentation/RCU/lockdep.txt         |   10 ------
 b/Documentation/RCU/rcu_dereference.txt |   33 +++++++--------------
 b/Documentation/RCU/whatisRCU.txt       |    2 -
 b/arch/x86/kernel/cpu/mcheck/mce.c      |   15 +++++----
 b/include/linux/rcupdate.h              |   50 --------------------------------
 6 files changed, 37 insertions(+), 93 deletions(-)