From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F204242089E for ; Tue, 7 Jul 2026 20:00:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783454419; cv=none; b=jE4plWkp2t6xCEjqEIz+0LA4tfmgB/G+DVrVWTPbh5XTBri/qeMcL72ExQ97fiTRXeHTysK+O0usK2pgM7LmYdFpyNu2LA+ikFlNKsSklQERsCYKZoCSGR/wmqnVpdzb6q6WOskzxWW4M4T8lF4VSapVXbaGmdhGWKcQZHjdkgk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783454419; c=relaxed/simple; bh=UlSR58uN6scwFgHtJxAiIrunGTFyfFZMQg3qOaXjUT4=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=UDzfyOBLws5hAE8dvbyT/zl2TDDeA8gp48I4X3ySw5+qS23Or0obKrUNrufe/y9UWZH5g24UKE+aYf6sH+g3fOdHI8XQzNV8qIHzr0hpTExTJ/7Cd2dt+KDq0DHMsCydgG85HUzjEAZzy1leS7Qt3yQ6O1Hm/M9SVuYLPFEhw+Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=tikSvhbg; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="tikSvhbg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7278F1F000E9; Tue, 7 Jul 2026 20:00:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1783454418; bh=Eu7d3Mg8WaYf5KSFPdcNilXxamD8nuaLU1MkLCXYPss=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=tikSvhbgBtdag1VIYmsxgHJeMj5DHNKMkHrq9SYpEQiw8APjklnXgZG+5dO3SbmiU +HW6c0NV/1ePIUKHFoKrDidjXbV40oispoiFkDZsVRsGOD4KD2XXC05ysgMw/bcnyl lBSb0Mh+36LhYeCk1YG8T4W3jk/OzhcLt425vW1M= Date: Tue, 7 Jul 2026 13:00:18 -0700 From: Andrew Morton To: Bradley Morgan Cc: pmladek@suse.com, feng.tang@linux.alibaba.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] panic: stop CPUs that lose the panic_redirect_cpu race Message-Id: <20260707130018.1281053fee6e981dcbcc0525@linux-foundation.org> In-Reply-To: <20260707183253.9793-1-include@grrlz.net> References: <20260707183253.9793-1-include@grrlz.net> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 7 Jul 2026 18:32:53 +0000 Bradley Morgan wrote: > Loser of the redirect cmpxchg must stop, not fall through to > panic_try_start(). > > This issue was found by sashiko [1]. > Thanks, I'll queue for test-n-review. > > Changes since v1: a nested panic on the CPU that already holds > panic_redirect_cpu would fail its own cmpxchg and, with v1's > unconditional return true, halt itself and abandon the panic. > Check old_cpu == this_cpu so the winner of a nested reentry > falls through to panic_try_start() instead. Sashiko ain't done yet: https://sashiko.dev/#/patchset/20260707183253.9793-1-include@grrlz.net