linux-kernel - [PATCH v4 tip/core/locking 0/4] Memory-barrier documentation updates

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Date:	Wed, 4 Dec 2013 14:46:28 -0800
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, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, dhowells@...hat.com,
	edumazet@...gle.com, darren@...art.com, fweisbec@...il.com,
	sbw@....edu
Subject: [PATCH v4 tip/core/locking 0/4] Memory-barrier documentation updates

Hello!

This series applies some long-needed updates to memory-barriers.txt:

1.	Add ACCESS_ONCE() calls where needed to ensure their inclusion
	in code copy-and-pasted from this file.

2.	Add long atomic examples alongside the existing atomics.

3.	Prohibit architectures supporting the Linux kernel from
	speculating stores.

4.	Document what ACCESS_ONCE() does along with a number of situations
	requiring its use.

Changes from v3:

o	Fix typos noted by Peter Zijlstra.

o	Added the documentation about ACCESS_ONCE(), which expands on
	http://thread.gmane.org/gmane.linux.kernel.mm/82891/focus=14696,
	ably summarized by Jon Corbet at http://lwn.net/Articles/508991/.

Changes from v2:

o	Update examples so that that load against which the subsequent
	store is to be ordered is part of the "if" condition.

o	Add an example showing how the compiler can remove "if"
	conditions and how to prevent it from doing so.

o	Add ACCESS_ONCE() to the compiler-barrier section.

o	Add a sentence noting that transitivity requires smp_mb().

Changes from v1:

o	Combined with Peter Zijlstra's speculative-store-prohibition patch.

o	Added more pitfalls to avoid when prohibiting speculative
	stores, along with how to avoid them.

o	Applied Josh Triplett's review comments.

							Thanx, Paul


 b/Documentation/memory-barriers.txt |  666 ++++++++++++++++++++++++++++--------
 1 file changed, 533 insertions(+), 133 deletions(-)

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