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

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Message-ID: <20150512211814.GA31939@linux.vnet.ibm.com>
Date:	Tue, 12 May 2015 14:18:14 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...nel.org, laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
	josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
	rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
	dvhart@...ux.intel.com, fweisbec@...il.com, oleg@...hat.com,
	bobby.prani@...il.com
Subject: [PATCH tip/core/rcu 0/4] 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(-)

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