From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8DB87C2D0EC for ; Fri, 27 Mar 2020 02:28:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6E79120B80 for ; Fri, 27 Mar 2020 02:28:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727830AbgC0C2l (ORCPT ); Thu, 26 Mar 2020 22:28:41 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:47832 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727650AbgC0C2k (ORCPT ); Thu, 26 Mar 2020 22:28:40 -0400 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jHejd-003hG3-Up; Fri, 27 Mar 2020 02:28:37 +0000 From: Al Viro To: Linus Torvalds Cc: Thomas Gleixner , x86@kernel.org, linux-kernel@vger.kernel.org Subject: [RFC][PATCH v2 6/8] x86: don't reload after cmpxchg in unsafe_atomic_op2() loop Date: Fri, 27 Mar 2020 02:28:34 +0000 Message-Id: <20200327022836.881203-6-viro@ZenIV.linux.org.uk> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200327022836.881203-1-viro@ZenIV.linux.org.uk> References: <20200327022836.881203-1-viro@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Al Viro lock cmpxchg leaves the current value in eax; no need to reload it. Signed-off-by: Al Viro --- arch/x86/include/asm/futex.h | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/arch/x86/include/asm/futex.h b/arch/x86/include/asm/futex.h index 53c07ab63762..d5d36f408ad0 100644 --- a/arch/x86/include/asm/futex.h +++ b/arch/x86/include/asm/futex.h @@ -34,17 +34,17 @@ do { \ do { \ int oldval = 0, ret, tem; \ asm volatile("1:\tmovl %2, %0\n" \ - "\tmovl\t%0, %3\n" \ + "2:\tmovl\t%0, %3\n" \ "\t" insn "\n" \ - "2:\t" LOCK_PREFIX "cmpxchgl %3, %2\n" \ - "\tjnz\t1b\n" \ - "3:\n" \ + "3:\t" LOCK_PREFIX "cmpxchgl %3, %2\n" \ + "\tjnz\t2b\n" \ + "4:\n" \ "\t.section .fixup,\"ax\"\n" \ - "4:\tmov\t%5, %1\n" \ + "5:\tmov\t%5, %1\n" \ "\tjmp\t3b\n" \ "\t.previous\n" \ - _ASM_EXTABLE_UA(1b, 4b) \ - _ASM_EXTABLE_UA(2b, 4b) \ + _ASM_EXTABLE_UA(1b, 5b) \ + _ASM_EXTABLE_UA(3b, 5b) \ : "=&a" (oldval), "=&r" (ret), \ "+m" (*uaddr), "=&r" (tem) \ : "r" (oparg), "i" (-EFAULT), "1" (0)); \ -- 2.11.0