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=1794777503; b=bv65qTfhwSb7dPQwLrw+Yst1yhlFWcOahGOhbZFj7j/PK6K0LCu51qFLtW2DY9Ce3ytd +hzRVV/aDxFz48U/C3QWj0c2rK2qn1kMKWKW2WzqwUGQS2uCiOvtC/1NIGqTqSm9OaOE+ lfLOmkdo5Ut11E8isvR/D09MdEzMN/dhmPt4gR6+RR/uAu6EpvemdKByl0urgsBfreLcn kLBsV2jmS84wJN+/FXrDt7EqfmEME3QK8z7ZAYXY6FnajiEjlXnDZNRuZL7c56vwmbkRy vkCta3YRjleyDob4E90OnK3O0DbcUIaYiVF3MMvQJyGg0bSf466jvtY0kbiw99zcp+w== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794777503; 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=4NmVekp5AF3TQlvKfhhoRjPEWciyBwoXsOkkxZlyMuo=; b=Zixe/hV+EdkILhAyiU9JZZvMDw+8FqFJMj2FOe3sBiZkYf/b8WsWRTIGXo688RSjaplm KQ3Gm9816PHj4S9LZ6poZoUjz8FaV57ppsyLt8LW8sbZwoFu2wDIqvrBeTjf2fo8lAjNF Fcvclc7a7LtBG0pDh2F0RdUIsJPgaG7yrRRP7cdXxWirXPmFAMWagai51CBCYv6hz1wPy 4hERNxVSpg5PBFYpv90fkzLivFx3hNv6cgaJn509wCoQd0tqAJHUzpl8N9D9CwUdCC0CS PC5690OjinszKbMEFFQ+C9ew4ZsWgM+ckFQ1guy3t5k7Ouoil4WV1iGXymXBvRrJTpQ== 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="EwsrI/yS"; 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 5A7AF606A32C; Sun, 15 Nov 2026 21:18:23 +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=EwsrI/yS Received: by smtp.kernel.org (Postfix) with ESMTPSA id E02E61F000C4; Sun, 15 Nov 2026 21:18:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794777503; bh=4NmVekp5AF3TQlvKfhhoRjPEWciyBwoXsOkkxZlyMuo=; h=From:Date:Subject:To:Cc; b=EwsrI/ySyvB20G0OXm5ps0iHqCR5WTS32bYIMIkp6kAmcrqApUPqMEqq+cvOy00uX ho4vyv2AUSFdsaQKdjVayMoQTcfrB2xGxXN0Vp4peDzCY5TJYQI/eBXKlFblLqQmt0 KckZyexpMFRvAR69YKm3wSJvWv1t2w6N3uZv6OppxZOw4UpobFwa2tv7WeOXTgLIyA Cxo02L3wPE8NOgJ/ynLbsnCI+iNFz9fa/IC8fnU2wrGrux6Foj5P1tJ/d4POnE7C/k 7uhcJ9BKJJZA9zrKIor1VA+oNivY260M9LERoMcVdvJGdzk1Ad/pat33zeEoN7bUvg pmMteI/xmOSxg== From: Nathan Chancellor Date: Sun, 15 Nov 2026 14:18:07 -0700 Subject: [PATCH] powerpc/xmon: Avoid unsequenced accesses to tsk in show_task() 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: <20261115-xmon-wunsequenced-v1-1-42ae3fe45bf4@kernel.org> X-B4-Tracking: v=1; b=H4sIAAAAAAAA/yXMQQrCMBBG4auUWRvoRBrBq4iLmP7VEZxqptFC6 d0bdfkt3lvIkAVGx2ahjLeYjFrBu4bSLeoVTvpq8q0PzNy5+TGq+xQ1vAo0oXfs24iYhkPYB6r dM2OQ+fc8nf+2crkjTd8RresGh06aTXUAAAA= X-Change-ID: 20261115-xmon-wunsequenced-120aeacf7636 To: Madhavan Srinivasan Cc: Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , "Ritesh Harjani (IBM)" , Shrikanth Hegde , Arnd Bergmann , linuxppc-dev@lists.ozlabs.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=2438; i=nathan@kernel.org; h=from:subject:message-id; bh=n3wmVZOyMNsX0uk3IiniOVaUBJnF2oOZEtO24z2uNpg=; b=kA0DAAoWHWsmkXHAGpYByyZiAGr6IZihRZbffcT0Cn4l0kQ9p2gOZzFH1xiWaOwkQ4z9Dio1B Ih1BAAWCgAdFiEEe+MlxzExnM0B2MqSHWsmkXHAGpYFAmr6IZgACgkQHWsmkXHAGpZYQAEA+JcF h7PyeMAe3s4nhbTb5HJ8VLD36RDIdTWqIVyIciABAI7Ee9Nul+Wz3OwRJenTiDaR5Ht50X9ChFl /YY2LYwQI 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_task(), which can break the build with CONFIG_PPC_WERROR=y / CONFIG_WERROR=y / W=e: arch/powerpc/xmon/xmon.c:3262:3: error: unsequenced accesses to volatile qualified 'tsk' [-Werror,-Wunsequenced] 3261 | printf("%16px %16lx %16px %6d %6d %c %2d %s\n", tsk, | ~~~ 3262 | tsk->thread.ksp, tsk->thread.regs, | ^ 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. tsk was made volatile in commit a2305e3de819 ("powerpc: mark local variables around longjmp as volatile") to ensure its value in show_tasks() was properly restored after returning from a potential longjmp(). Aside from that, the value is not being modified through other means, so rename the volatile parameter and add a local variable named tsk to hold its value throughout show_task(), clearing up the warning. Cc: stable@vger.kernel.org Fixes: a2305e3de819 ("powerpc: mark local variables around longjmp as volatile") Closes: https://github.com/ClangBuiltLinux/linux/issues/2199 Link: https://github.com/llvm/llvm-project/commit/955715460eaf9188c241c74750637fc82dfcc423 [1] Signed-off-by: Nathan Chancellor --- arch/powerpc/xmon/xmon.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c index cb3a3244ae6f..90a8d7a8f42d 100644 --- a/arch/powerpc/xmon/xmon.c +++ b/arch/powerpc/xmon/xmon.c @@ -3240,8 +3240,9 @@ memzcan(void) printf("%.8lx\n", a - mskip); } -static void show_task(struct task_struct *volatile tsk) +static void show_task(struct task_struct *volatile vol_tsk) { + struct task_struct *tsk = vol_tsk; unsigned int p_state = READ_ONCE(tsk->__state); char state; --- base-commit: 7475ea8b58616b33c04afb976cf0fbaad9dd63fb base-tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master change-id: 20261115-xmon-wunsequenced-120aeacf7636 Best regards, -- Cheers, Nathan