[PATCH tip/core/rcu 0/4] Array-based RCU removals for 4.2

From: Paul E. McKenney
Date: Tue May 12 2015 - 17:18:27 EST


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(-)

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