From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from confino.investici.org (confino.investici.org [93.190.126.19]) (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 138DF420867 for ; Tue, 7 Jul 2026 20:01:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=93.190.126.19 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783454466; cv=none; b=bR2Z0VTGcys/U6dbxACmbf1RGkXjxu0Qc6o0xbe0hLclNzthogXlfRU5bFVEn2yYxdOhD6erh2ZidmqfDErQT7J8yG6nj5S2mJBXPtr+vogCODEP+pYSXFEaEdXXJ8xweb476i+KW1GAQrOMUMvJFrQhoCyW/gHasy7RdBcdf9c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783454466; c=relaxed/simple; bh=3kgiHJ+1tkDBI6GdTNop8Vl9A2hW84CegvtVWd+4rO8=; h=Date:From:To:CC:Subject:In-Reply-To:References:Message-ID: MIME-Version:Content-Type; b=YlppIskxWcOt1vCPT+6OnBjjzzVLrnNlMp3ypdWdomhM1cwEhQqcjVHZapyLIPgolcG5nyfnWYL4cuIykXiLJQ4fCISA52HCC2vh/4UmVA4BCHIRsCz6DN86Dk+hL/sEVDO4gwOIXd6MKzTfD9fkxjhZuo9H1M/C0ZnOFz79Gm8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=grrlz.net; spf=pass smtp.mailfrom=grrlz.net; dkim=pass (1024-bit key) header.d=grrlz.net header.i=@grrlz.net header.b=tNz8/fCA; arc=none smtp.client-ip=93.190.126.19 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=grrlz.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=grrlz.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=grrlz.net header.i=@grrlz.net header.b="tNz8/fCA" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=grrlz.net; s=stigmate; t=1783454460; bh=J5NKvepBgLdAcvK+A0sjAxW3yvgFRD4VKkZeZRE6CMs=; h=Date:From:To:CC:Subject:In-Reply-To:References:From; b=tNz8/fCALGEySqUc8DrSM6bFGrqTfPqtKXRr7yiSiHER+xYdUQHPbSxHWa3Qo7Au7 bDLJl2Ig745dq/YaxJ0rWEPy2x21FRNndtIoQpMB2OzKkGariGyeyEb7qMzwE956xu XpLtxSZwa7npBlLnYgUQIIfZU3AA7KgaZYQLhOmU= Received: from mx1.investici.org (unknown [127.0.0.1]) by confino.investici.org (Postfix) with ESMTP id 4gvsY84Z6lz1104; Tue, 07 Jul 2026 20:01:00 +0000 (UTC) Received: by mx1.investici.org (Postfix) id 4gvsY80llPz10yx; Tue, 07 Jul 2026 20:01:00 +0000 (UTC) Date: Tue, 07 Jul 2026 21:01:01 +0100 From: Bradley Morgan To: Andrew Morton 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 In-Reply-To: <20260707130018.1281053fee6e981dcbcc0525@linux-foundation.org> References: <20260707183253.9793-1-include@grrlz.net> <20260707130018.1281053fee6e981dcbcc0525@linux-foundation.org> Message-ID: <142D949B-F73A-4D2F-BB77-C5F9A4D8003F@grrlz.net> 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=utf-8 Content-Transfer-Encoding: 8bit On July 7, 2026 9:00:18 PM GMT+01:00, Andrew Morton wrote: >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 > > oh absolutely great Thanks!