From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752979AbcD1K3I (ORCPT ); Thu, 28 Apr 2016 06:29:08 -0400 Received: from terminus.zytor.com ([198.137.202.10]:47040 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752676AbcD1K3F (ORCPT ); Thu, 28 Apr 2016 06:29:05 -0400 Date: Thu, 28 Apr 2016 03:28:22 -0700 From: tip-bot for David Howells Message-ID: Cc: paulmck@linux.vnet.ibm.com, tglx@linutronix.de, peterz@infradead.org, mingo@kernel.org, linux-kernel@vger.kernel.org, dhowells@redhat.com, torvalds@linux-foundation.org, hpa@zytor.com Reply-To: hpa@zytor.com, dhowells@redhat.com, torvalds@linux-foundation.org, mingo@kernel.org, linux-kernel@vger.kernel.org, paulmck@linux.vnet.ibm.com, tglx@linutronix.de, peterz@infradead.org In-Reply-To: <1461691328-5429-2-git-send-email-paulmck@linux.vnet.ibm.com> References: <1461691328-5429-2-git-send-email-paulmck@linux.vnet.ibm.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:locking/core] locking/Documentation: State purpose of memory-barriers.txt Git-Commit-ID: 8d4840e84871847ee1bae56a776907d08a9265f7 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 8d4840e84871847ee1bae56a776907d08a9265f7 Gitweb: http://git.kernel.org/tip/8d4840e84871847ee1bae56a776907d08a9265f7 Author: David Howells AuthorDate: Tue, 26 Apr 2016 10:22:06 -0700 Committer: Ingo Molnar CommitDate: Thu, 28 Apr 2016 10:57:51 +0200 locking/Documentation: State purpose of memory-barriers.txt There has been some confusion about the purpose of memory-barriers.txt, so this commit adds a statement of purpose. Signed-off-by: David Howells Signed-off-by: Paul E. McKenney Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: corbet@lwn.net Cc: dave@stgolabs.net Cc: linux-doc@vger.kernel.org Cc: will.deacon@arm.com Link: http://lkml.kernel.org/r/1461691328-5429-2-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar --- Documentation/memory-barriers.txt | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt index fb2dd35..8b11e54 100644 --- a/Documentation/memory-barriers.txt +++ b/Documentation/memory-barriers.txt @@ -19,6 +19,22 @@ in case of any doubt (and there are many) please ask. To repeat, this document is not a specification of what Linux expects from hardware. +The purpose of this document is twofold: + + (1) to specify the minimum functionality that one can rely on for any + particular barrier, and + + (2) to provide a guide as to how to use the barriers that are available. + +Note that an architecture can provide more than the minimum requirement +for any particular barrier, but if the architecure provides less than +that, that architecture is incorrect. + +Note also that it is possible that a barrier may be a no-op for an +architecture because the way that arch works renders an explicit barrier +unnecessary in that case. + + ======== CONTENTS ========