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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6513DC6FA82 for ; Mon, 12 Sep 2022 04:57:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229729AbiILE5N (ORCPT ); Mon, 12 Sep 2022 00:57:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54738 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229656AbiILE44 (ORCPT ); Mon, 12 Sep 2022 00:56:56 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D8FAD286C3 for ; Sun, 11 Sep 2022 21:56:44 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 77E6760EF7 for ; Mon, 12 Sep 2022 04:56:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D2395C433D6; Mon, 12 Sep 2022 04:56:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1662958603; bh=sI32LaUligPVDGLiu+bIKkJ+agXYZDcXjp7l+IYNL64=; h=Date:To:From:Subject:From; b=KKCwD2IOIbzEGI+FD6soFuzc5YQ90AQNBdQmmwgBGW0uKT0EN+b48Jc8cqkvyDwka an9ZiT5lpGxtnnnabA7JOsM7tvWD3rAuyzqy5r3ijtjklDFoLd8V6z3xT9QHLpZDaf 9p/aWnUZknRzCuFr+30BCxk5vRQ7kFeAfr32B+m0= Date: Sun, 11 Sep 2022 21:56:43 -0700 To: mm-commits@vger.kernel.org, ubizjak@gmail.com, akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-nonmm-stable] bitops-use-try_cmpxchg-in-set_mask_bits-and-bit_clear_unless.patch removed from -mm tree Message-Id: <20220912045643.D2395C433D6@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The quilt patch titled Subject: bitops: use try_cmpxchg in set_mask_bits and bit_clear_unless has been removed from the -mm tree. Its filename was bitops-use-try_cmpxchg-in-set_mask_bits-and-bit_clear_unless.patch This patch was dropped because it was merged into the mm-nonmm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Uros Bizjak Subject: bitops: use try_cmpxchg in set_mask_bits and bit_clear_unless Date: Mon, 22 Aug 2022 16:38:51 +0200 Use try_cmpxchg instead of cmpxchg (*ptr, old, new) == old in set_mask_bits and bit_clear_unless. x86 CMPXCHG instruction returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg). Also, try_cmpxchg implicitly assigns old *ptr value to "old" when cmpxchg fails, enabling further code simplifications. Link: https://lkml.kernel.org/r/20220822143851.3290-1-ubizjak@gmail.com Signed-off-by: Uros Bizjak Signed-off-by: Andrew Morton --- include/linux/bitops.h | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) --- a/include/linux/bitops.h~bitops-use-try_cmpxchg-in-set_mask_bits-and-bit_clear_unless +++ a/include/linux/bitops.h @@ -328,10 +328,10 @@ static __always_inline void __assign_bit const typeof(*(ptr)) mask__ = (mask), bits__ = (bits); \ typeof(*(ptr)) old__, new__; \ \ + old__ = READ_ONCE(*(ptr)); \ do { \ - old__ = READ_ONCE(*(ptr)); \ new__ = (old__ & ~mask__) | bits__; \ - } while (cmpxchg(ptr, old__, new__) != old__); \ + } while (!try_cmpxchg(ptr, &old__, new__)); \ \ old__; \ }) @@ -343,11 +343,12 @@ static __always_inline void __assign_bit const typeof(*(ptr)) clear__ = (clear), test__ = (test);\ typeof(*(ptr)) old__, new__; \ \ + old__ = READ_ONCE(*(ptr)); \ do { \ - old__ = READ_ONCE(*(ptr)); \ + if (old__ & test__) \ + break; \ new__ = old__ & ~clear__; \ - } while (!(old__ & test__) && \ - cmpxchg(ptr, old__, new__) != old__); \ + } while (!try_cmpxchg(ptr, &old__, new__)); \ \ !(old__ & test__); \ }) _ Patches currently in -mm which might be from ubizjak@gmail.com are