From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794717718; b=u18uZ/xmwtmsbBtBTanmwcM1lTsfQsbEqEA7xN/taPlgLN4ePPw6G76I3V0kP5JyTRWc gVaYtTvSHyBRWEsZCB+QXSlFXiDHfvYSgfzyC3OUBdFN9U6sS7/LhUyjILH+ys6eCtHGl VpwJKzCkxpJTt+jm/e97qV05GF/iQX0DyODWddXFu6PCg1BpAkEYyLDtRwRVIVtkc8bcP xfL4bZgtDNeOLaNxpkfGsVjPsAuSeaQHOFjXtBjPuWK4hsw/JOBCDmEn7ygjJbXeAcgYq JAeEiCor5WFrmcE3WLHzf9YakDCmKJaEI/bhBnyya45jWZLP8Ow1rWD/fOXtgkwk0ug== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794717718; h=Received:DKIM-Signature:From:Date:Subject:MIME-Version:Content-Type: Content-Transfer-Encoding:Message-Id:X-B4-Tracking:X-Change-ID:To:Cc: X-Mailer:X-Developer-Signature:X-Developer-Key; bh=ietY+R83A5Uk3+FsvAUo+7mwsEnw74vKAWiPVPCniTM=; b=jBKi08fix9dwiWDO6VyBNLFTKgQ20Yg3fxbSzQKpRUJWQJQh6k8utKeHuk0zNODKRZcE 8J1P2lVSbd5RwoTGd3WAW37rnhUk7v1RuNodmihkGx1ndWGc4H0v2mm0oiMbBBFJzS7c1 65Sk+1XA91FBDpmewI08qistJLHQe4QpldO0EBMTNG1IO/LpHVlT1ZiLMuCW09hc8dY/9 XrurWpF8Vx80xx67R8WOYF5mpt1Yw3KrAFZkYlkwI5UrOzKfc0ndhn0AjZYaoFQZFJOAP 8TTHfE6H6IL9rg7GsUYs2b9eLrjyGDMa3nJkOjoVCPKa4kcoRebRuxaZTNx56xlwbQA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=eZxgZ0lP; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3E040606A327; Sun, 15 Nov 2026 04:41:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=eZxgZ0lP Received: by smtp.kernel.org (Postfix) with ESMTPSA id 635C21F000C4; Sun, 15 Nov 2026 04:41:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794717717; bh=ietY+R83A5Uk3+FsvAUo+7mwsEnw74vKAWiPVPCniTM=; h=From:Date:Subject:To:Cc; b=eZxgZ0lPsCQ+o+1TLpSa7upV4rnbXh8kV5XoJUJD1D0QmM2Etj/E3fCieSyZMHe0R ixUdyNF7kBqVdiRLtu2TD/Q+OfHaQvB5j7Qm4bGsJsEa0uYNDoyZdQ9ak5xw4A0M5O My/hPi1wURYCf+e4jAI/knbu9XkLOIvY/ywqluy84jTOgkaFurH2ZdtK67Bfv6hRVv HQZTgrVQb/UeSvs83/JtXXCY3JKhldYSRpPH6zJmOxjqgovCdMXitgwFz6JlIM18r0 XWVY1cNyQ2Moa1ZLiveWIyy9VLSAqy2WCjKSdDQG6ce4EDARJasaee+iWTsTiVylDk GW9YZxjPPFtCQ== From: Nathan Chancellor Date: Sat, 14 Nov 2026 21:41:48 -0700 Subject: [PATCH] floppy: Avoid unsequenced accesses to jiffies in show_floppy() X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261114-floppy-wunsequenced-v1-1-a54dba6754c4@kernel.org> X-B4-Tracking: v=1; b=H4sIAAAAAAAA/yXMSw6CMBRG4a2QO7YJRSLFrRgHtv2BS0ypvdZHC Hu36vAbnLOSIDGEjtVKCQ8WXkKB3lXkpksYodgXU1M3B611q4brEuNbPXMQ3DKCg1fGdvve18a atqdSxoSBX7/r6fy3ZDvD3b8r2rYPaPADu3cAAAA= X-Change-ID: 20261114-floppy-wunsequenced-8b739d08b849 To: Denis Efremov , Jens Axboe Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, stable@vger.kernel.org, Nathan Chancellor X-Mailer: b4 0.17-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=2058; i=nathan@kernel.org; h=from:subject:message-id; bh=QwSxB0h0kSn5HyXRP9tGT4oF+hJsuq19SjwCHgkj9hU=; b=owGbwMvMwCUmm602sfCA1DTG02pJDFk/LQSaGJzaOZPnM7teKJg859HpF2fDHs1f9er/f/uZ7 We84idv6ihlYRDjYpAVU2Spfqx63NBwzlnGG6cmwcxhZQIZwsDFKQATyephZDggzZTpWfaV7+7K LwJrF+pfCf34quPYJQ2hHP7r73Wt8l8y/GYRnqx1RkIgRvHmvObZ36XjH7Mte92s6nu2dPljnzS Ri3wA X-Developer-Key: i=nathan@kernel.org; a=openpgp; fpr=2437CB76E544CB6AB3D9DFD399739260CB6CB716 After a recent improvement in clang to warn on unsequenced accesses to volatile variables [1], an instance appears in show_floppy(), which can break the build with CONFIG_WERROR=y / W=e: drivers/block/floppy.c:1839:30: error: unsequenced accesses to volatile qualified 'jiffies' [-Werror,-Wunsequenced] 1839 | jiffies, interruptjiffies, jiffies - interruptjiffies, | ~~~~~~~ ^ Per C11 5.1.2.3.2, accessing a volatile object is a side effect. Per C11 6.5.2, unsequenced side effects on the same scalar object are undefined behavior. Per C11 6.5.2.2.10/12, the evaluation of arguments in a function call is indeterminately sequenced, meaning any side effects in the arguments are unsequenced. Add a local variable to hold the value of jiffies before the function call so that there are no unsequenced side effects, clearing up the warning. Cc: stable@vger.kernel.org Closes: https://github.com/ClangBuiltLinux/linux/issues/2198 Link: https://github.com/llvm/llvm-project/commit/955715460eaf9188c241c74750637fc82dfcc423 [1] Signed-off-by: Nathan Chancellor --- drivers/block/floppy.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c index c677d783811f..f6339d779be9 100644 --- a/drivers/block/floppy.c +++ b/drivers/block/floppy.c @@ -1830,13 +1830,14 @@ static void reset_fdc(void) static void show_floppy(int fdc) { + unsigned long j = jiffies; int i; pr_info("\n"); pr_info("floppy driver state\n"); pr_info("-------------------\n"); pr_info("now=%lu last interrupt=%lu diff=%lu last called handler=%ps\n", - jiffies, interruptjiffies, jiffies - interruptjiffies, + j, interruptjiffies, j - interruptjiffies, lasthandler); pr_info("timeout_message=%s\n", timeout_message); --- base-commit: ab43ec385580b8f8abf72d70fa3acbf4e4f098a5 change-id: 20261114-floppy-wunsequenced-8b739d08b849 Best regards, -- Cheers, Nathan