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 C4906C636D4 for ; Wed, 1 Feb 2023 18:40:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230295AbjBASkZ (ORCPT ); Wed, 1 Feb 2023 13:40:25 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45580 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230508AbjBASkR (ORCPT ); Wed, 1 Feb 2023 13:40:17 -0500 Received: from mail-pf1-x431.google.com (mail-pf1-x431.google.com [IPv6:2607:f8b0:4864:20::431]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 47ED037F1D for ; Wed, 1 Feb 2023 10:39:59 -0800 (PST) Received: by mail-pf1-x431.google.com with SMTP id ay1so13148290pfb.7 for ; Wed, 01 Feb 2023 10:39:59 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rivosinc-com.20210112.gappssmtp.com; s=20210112; h=to:cc:date:message-id:subject:mime-version :content-transfer-encoding:from:from:to:cc:subject:date:message-id :reply-to; bh=1bheOv+RMKsLccw364mds17HOO0bJItYyH4Drs1sYdU=; b=jMwdNnyeAncNolb8weAVUSEgRK9/0nmbRFJNgQmN9mMPSeUebPlB9TqqZpZHT9wWxe Vl7R/xpSk9DBsVswONwOZLpCl/uJ/X/6e3UcOEAJg6ah25SHNlEB88qrzHXFk4QRKQ7C 7aKvLRrpp8VShSED5q8sQYBsyKoLWXYf9vFpm4wAxmgm81LkQJLIXBxLvwvLx80PppKb bkEwsK5gr/aiz/7OW/YEDesYKQ4CSSKj/9yVGKZtoIE0wjRaiobXcnRLwNTjA1aDilPs kB8klU3HaJcTd9i+HXdoUjVRASTWuE1whgoyEhW6bU5BQ3JoWjed2fr8Puzj/iz9ef58 uBgw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=to:cc:date:message-id:subject:mime-version :content-transfer-encoding:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=1bheOv+RMKsLccw364mds17HOO0bJItYyH4Drs1sYdU=; b=ukr7tQtQTEIXkFTSx+/9CL7fcAuzFzv6nDmatopI7kDrRdu/06rDymPNVMcgEZb3J7 X5//JifqNdb+ogSGMsuZspSylsKhuhOvsC0QF6AaEdN5OljGMz6N7uophB7jx+b8VUXi +2TLlRH83Gbt7hRELQ22MUHJ6+3e1oXnAb/8bYODBia9sPV+rxnU72winZWm+6MsVeFQ ocfg88MlN1lqKdz3KjozfKoyGz6ZtTqU0pntw7h9xtPcXUmXp6h2mD7jnDlzrP3EfeDW 1ePICsAwaFkaglCsrLhylTBXb8CsD/g7sPoEEJQmFaM5SxzL5WebxsRPEew+Ma9iSOJO tkCA== X-Gm-Message-State: AO0yUKUNFYjCL5yLqAKPaDRLZtpm9o1/MhyTmjRu+UKQI1kS7ItEFRZU ike6BWgv+J6CtpIAo78p0HHNPA== X-Google-Smtp-Source: AK7set+QBqSRHAUKmIFDrFVmv4riYVpG6AHQn0FUNOQJ/lawfEfaqiRxrWELEe0uPX4Ux8PpgKmxfg== X-Received: by 2002:aa7:9af1:0:b0:57a:7140:84ae with SMTP id y17-20020aa79af1000000b0057a714084aemr3328095pfp.9.1675276791927; Wed, 01 Feb 2023 10:39:51 -0800 (PST) Received: from smtpclient.apple ([51.52.155.79]) by smtp.gmail.com with ESMTPSA id y84-20020a626457000000b00582579cb0e0sm11741320pfb.129.2023.02.01.10.39.50 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 01 Feb 2023 10:39:51 -0800 (PST) From: Matt Evans Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3696.120.41.1.1\)) Subject: [PATCH] locking/atomic: cmpxchg: Make __generic_cmpxchg_local compare against zero-extended 'old' value Message-Id: <8B94CEAB-63AD-400F-A5CD-31AC4490EF4C@rivosinc.com> Date: Wed, 1 Feb 2023 18:39:48 +0000 Cc: Palmer Dabbelt To: Arnd Bergmann , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org X-Mailer: Apple Mail (2.3696.120.41.1.1) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org __generic_cmpxchg_local takes unsigned long old/new arguments which might end up being up-cast from smaller signed types (which will sign-extend). The loaded compare value must be compared against a truncated smaller type, so down-cast appropriately for each size. The issue is apparent on 64-bit machines with code, such as atomic_dec_unless_positive(), that sign-extends from int. 64-bit machines generally don't use the generic cmpxchg but development/early ports might make use of it, so make it correct. Signed-off-by: Matt Evans --- include/asm-generic/cmpxchg-local.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/include/asm-generic/cmpxchg-local.h = b/include/asm-generic/cmpxchg-local.h index 380cdc824e4b..c3e7315b7c1d 100644 --- a/include/asm-generic/cmpxchg-local.h +++ b/include/asm-generic/cmpxchg-local.h @@ -26,15 +26,15 @@ static inline unsigned long = __generic_cmpxchg_local(volatile void *ptr, raw_local_irq_save(flags); switch (size) { case 1: prev =3D *(u8 *)ptr; - if (prev =3D=3D old) + if (prev =3D=3D (u8)old) *(u8 *)ptr =3D (u8)new; break; case 2: prev =3D *(u16 *)ptr; - if (prev =3D=3D old) + if (prev =3D=3D (u16)old) *(u16 *)ptr =3D (u16)new; break; case 4: prev =3D *(u32 *)ptr; - if (prev =3D=3D old) + if (prev =3D=3D (u32)old) *(u32 *)ptr =3D (u32)new; break; case 8: prev =3D *(u64 *)ptr; --=20 2.30.2