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=-2.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 265D0C43331 for ; Wed, 13 Nov 2019 10:24:15 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id ECC79222C1 for ; Wed, 13 Nov 2019 10:24:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="DtNaU69c"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="vkoHFrFW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org ECC79222C1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=/pRF8G1SceIz1f1F0NztDTwSnToutFm44kyPl5JPwt0=; b=DtNaU69cAVHHwj XIE03DOiZRjYmKWqFUS/6tVBgQYWSP/n8k7o4i3VhkT352RSIGsZM/BylsBVcUfm0Pcdt2TGyAC7x tcXPlHm9sh39T5E+DCR+d20pexOSo6rK6bb472Gwr1UOR1Alz7GHjifC3+IqmRpsw7vuXdv+x+y6a IqxarKy7VlN0xvUgLk2/a+EJQINZKls7DIvP6Wd7C5djzvCPbxz+JONEV5KOUPa0yJBUi5OAXfwzw b0FI5fyQ8ppF8uX6kae4cclG+im+PlMky5ThRZlreK00B9QfVsWo9o5zjUmDTXbiUuHyYnX9Mkm9B 4SeOUGtZIQWTV1Blfjjw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iUpok-0004co-Rw; Wed, 13 Nov 2019 10:24:06 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1iUpoh-0004cQ-FC for linux-arm-kernel@lists.infradead.org; Wed, 13 Nov 2019 10:24:04 +0000 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4396D222C1; Wed, 13 Nov 2019 10:24:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573640643; bh=ORAZV8c4f8R1ApOoI1BE23utHyso6gzFfy189+ri230=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=vkoHFrFWIiShRIxqfVRikTkXJR1MkCX3YKD7VP6IqjiC0eaULmNoE6thsfbO8PhJE d4CJg+0i1o9DCtJY45bD6btuwqIMxflnQGbSND873mf5Eg7Sw6+WXy18q8xrqtPNpc ljRNRVOL8dd0qgB+vr6RukkEejxwPA6HkawFMS4k= Date: Wed, 13 Nov 2019 10:23:58 +0000 From: Will Deacon To: Linus Torvalds Subject: Re: [PATCH v2] buffer: Fix I/O error due to ARM read-after-read hazard Message-ID: <20191113102357.GA25875@willie-the-truck> References: <20191112130244.16630-1-vincent.whitchurch@axis.com> <20191112160855.GA22025@arrakis.emea.arm.com> <20191112180034.GB19889@willie-the-truck> <20191112182249.GB22025@arrakis.emea.arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191113_022403_531482_C4B2D866 X-CRM114-Status: GOOD ( 11.77 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jens Axboe , Richard Earnshaw , Vincent Whitchurch , Catalin Marinas , Vincent Whitchurch , Russell King - ARM Linux , Linux Kernel Mailing List , Linux ARM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Nov 12, 2019 at 10:39:01AM -0800, Linus Torvalds wrote: > On Tue, Nov 12, 2019 at 10:22 AM Catalin Marinas > wrote: > > > > OK, so this includes changing test_bit() to perform a READ_ONCE. > > That's not going to happen. Ok, I'll stick my neck out here, but if test_bit() is being used to read a bitmap that is being concurrently modified (e.g. by set_bit() which boils down to atomic_long_or()), then why isn't READ_ONCE() required? Right now, test_bit takes a 'const volatile unsigned long *addr' argument, so I don't see that you'll get a change in codegen except on alpha and, with this erratum, arm32. Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel