From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932592AbdJXKW4 (ORCPT ); Tue, 24 Oct 2017 06:22:56 -0400 Received: from foss.arm.com ([217.140.101.70]:53018 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932498AbdJXKWu (ORCPT ); Tue, 24 Oct 2017 06:22:50 -0400 From: Will Deacon To: mingo@kernel.org Cc: linux-kernel@vger.kernel.org, Will Deacon , "Paul E. McKenney" Subject: [PATCH v2 2/5] locking/barriers: Add implicit smp_read_barrier_depends() to READ_ONCE() Date: Tue, 24 Oct 2017 11:22:47 +0100 Message-Id: <1508840570-22169-3-git-send-email-will.deacon@arm.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1508840570-22169-1-git-send-email-will.deacon@arm.com> References: <1508840570-22169-1-git-send-email-will.deacon@arm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In preparation for the removal of lockless_dereference(), which is the same as READ_ONCE() on all architectures other than Alpha, add an implicit smp_read_barrier_depends() to READ_ONCE() so that it can be used to head dependency chains on all architectures. Cc: Ingo Molnar Cc: "Paul E. McKenney" Signed-off-by: Will Deacon --- include/linux/compiler.h | 1 + 1 file changed, 1 insertion(+) diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 08083186e54f..7d7b77da9716 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -242,6 +242,7 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s __read_once_size(&(x), __u.__c, sizeof(x)); \ else \ __read_once_size_nocheck(&(x), __u.__c, sizeof(x)); \ + smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \ __u.__val; \ }) #define READ_ONCE(x) __READ_ONCE(x, 1) -- 2.1.4