From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756093Ab3KVT1H (ORCPT ); Fri, 22 Nov 2013 14:27:07 -0500 Received: from e33.co.us.ibm.com ([32.97.110.151]:45671 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755334Ab3KVT1C (ORCPT ); Fri, 22 Nov 2013 14:27:02 -0500 Date: Fri, 22 Nov 2013 11:26:57 -0800 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu Subject: [PATCH v3 tip/core/locking 0/3] Memory-barrier documentation updates Message-ID: <20131122192657.GA11924@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13112219-0928-0000-0000-000003B239C9 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. 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