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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 227C3E7DF1F for ; Mon, 2 Feb 2026 19:13:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc: To:From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=cjT2P46cgvM3nyh/kXEjvqkxlTx4XGDlaIbAn45KjYw=; b=LzBvAf6Zx1jvB4qt7SUB9ZQN6D 3JzIP+ppOBqKfDwYF8zVvnBGqhJAoyC2EUIfQKrm16WKJpZpohiU1ovAfqDyOQ5Lr09jk7GVzbV+G tBXtXvbFtnGrJY4P0kgtrNPA1tOqCwEiRR+1pqlRn+dFn9O0xeH5I8QF9UuH48Pd6oHUB8Hy0E2fE r9rR5PIXcjp0JFUzvMvJB980CVtpbGoPxX3T1n0PlrUT1FoZrVqnnAWh9Xw3B8fNPoXJ5nSxIIr0N Qzik/gxqkcOqa/4GXMJrNo2+oK3IFDqdhux6Ge3+DAe2ClTU8eTFAlOnNDo/+pdAgQWs/+Lb9gOfH T0mDHRAA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vmzMw-00000005UZd-3DuK; Mon, 02 Feb 2026 19:13:54 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vmzMu-00000005UYn-1cgZ for linux-arm-kernel@lists.infradead.org; Mon, 02 Feb 2026 19:13:53 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 545FA405C4; Mon, 2 Feb 2026 19:13:51 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 460A6C116C6; Mon, 2 Feb 2026 19:13:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770059631; bh=bVNExOecclgFUYczf53ULyUIujXLZbcCGWlArLy5Srg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qo2fkX6zhNO6/ZZPfsT8pTBSn1FSKNP/wNRp/EdO9cTMiPLJ/eGxI1hE2ANyGtNzX QITb/IWbFQcM4r8psiYTvSpQqbQpK4V13ZBGX9r30D0a/hQ1685/7Tpui/FrMn7WpV k+w0yrEqANMg39VBGvxKgmsIXBJHIhxrpDbM3cBShUptCBsuUFiJbIRXjqB+HEbgCc 9Y1pZjNDXa5zjR67NSYuKezM7oNUubB7Rv54usQsKE+5H0eCjIvregkNuoYC9Dwxa7 hur9/BMjEOL+fv7de+8QFvepcTwn0S30cRRU6mnhtZ2CoWWjS0uIiuShvhjcPS3Fg1 dL9TTdPYbcGlQ== From: Will Deacon To: Peter Zijlstra , Marco Elver Cc: catalin.marinas@arm.com, kernel-team@android.com, Will Deacon , Ingo Molnar , Thomas Gleixner , Boqun Feng , Waiman Long , Bart Van Assche , llvm@lists.linux.dev, David Laight , Arnd Bergmann , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 0/3] arm64: Fixes for __READ_ONCE() with CONFIG_LTO=y Date: Mon, 2 Feb 2026 19:13:42 +0000 Message-ID: <177004685649.2187917.2406852216797394665.b4-ty@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260130132951.2714396-1-elver@google.com> References: <20260130132951.2714396-1-elver@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260202_111352_448145_B089AD2B X-CRM114-Status: GOOD ( 11.48 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, 30 Jan 2026 14:28:23 +0100, Marco Elver wrote: > While investigating a Clang Context Analysis [1] false positive [2], I started > to dig deeper into arm64's __READ_ONCE() implementation with LTO. That rabbit > hole led me to find one critical bug with the current implementation (patch 1), > and subtle improvements that then enabled me to fix the original false positive. > > Patch 1 fixes a bug where READ_ONCE() on types larger than 8 bytes (non-atomic > fallback) incorrectly qualified the pointer rather than the pointee as volatile. > This resulted in a lack of "once" semantics for large struct loads. > > [...] Applied first patch only to arm64 (for-next/core), thanks! [1/3] arm64: Fix non-atomic __READ_ONCE() with CONFIG_LTO=y https://git.kernel.org/arm64/c/bb0c99e08ab9 Cheers, -- Will https://fixes.arm64.dev https://next.arm64.dev https://will.arm64.dev