From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com ([209.132.183.28]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1XmVuz-0003WG-UN for kexec@lists.infradead.org; Thu, 06 Nov 2014 22:52:42 +0000 Message-ID: <545BFB95.5030706@redhat.com> Date: Thu, 06 Nov 2014 17:52:05 -0500 From: Prarit Bhargava MIME-Version: 1.0 Subject: Re: [PATCH v8] kernel, add panic_on_warn References: <1415187736-16242-1-git-send-email-prarit@redhat.com> <545B733C.6080903@redhat.com> <20141106220731.GA13590@redhat.com> In-Reply-To: <20141106220731.GA13590@redhat.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Vivek Goyal Cc: Andi Kleen , Jonathan Corbet , jbaron@akamai.com, kexec@lists.infradead.org, Rusty Russell , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Fabian Frederick , isimatu.yasuaki@jp.fujitsu.com, "H. Peter Anvin" , Masami Hiramatsu , David Rientjes , Andrew Morton , linux-api@vger.kernel.org On 11/06/2014 05:07 PM, Vivek Goyal wrote: > On Thu, Nov 06, 2014 at 01:57:36PM -0800, David Rientjes wrote: > > [..] >> You see that doing >> >> if (panic_on_warn) { >> panic_on_warn = 0; >> panic(...); >> } >> >> is racy, I hope. If two threads WARN() at the same time, then there's >> nothing preventing a double panic() because WARN() itself is not >> serialized against anything. So both the current comment and your >> suggested revision comment are bogus. > > panic() is serialized on panic_lock. So I guess it is fine to hit WARN() > on multiple cpus. Do you see an issue there? Oops -- didn't see this until just now. Once again, Vivek beat me to the punch :) and much more succinctly than I will ever be able to do. :) P. > > Thanks > Vivek > _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec From mboxrd@z Thu Jan 1 00:00:00 1970 From: Prarit Bhargava Subject: Re: [PATCH v8] kernel, add panic_on_warn Date: Thu, 06 Nov 2014 17:52:05 -0500 Message-ID: <545BFB95.5030706@redhat.com> References: <1415187736-16242-1-git-send-email-prarit@redhat.com> <545B733C.6080903@redhat.com> <20141106220731.GA13590@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20141106220731.GA13590-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" Errors-To: kexec-bounces+glkk-kexec=m.gmane.org-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org To: Vivek Goyal Cc: Andi Kleen , Jonathan Corbet , jbaron-JqFfY2XvxFXQT0dZR+AlfA@public.gmane.org, kexec-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Rusty Russell , linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Fabian Frederick , isimatu.yasuaki-+CUm20s59erQFUHtdCDX3A@public.gmane.org, "H. Peter Anvin" , Masami Hiramatsu , David Rientjes , Andrew Morton , linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-api@vger.kernel.org On 11/06/2014 05:07 PM, Vivek Goyal wrote: > On Thu, Nov 06, 2014 at 01:57:36PM -0800, David Rientjes wrote: > > [..] >> You see that doing >> >> if (panic_on_warn) { >> panic_on_warn = 0; >> panic(...); >> } >> >> is racy, I hope. If two threads WARN() at the same time, then there's >> nothing preventing a double panic() because WARN() itself is not >> serialized against anything. So both the current comment and your >> suggested revision comment are bogus. > > panic() is serialized on panic_lock. So I guess it is fine to hit WARN() > on multiple cpus. Do you see an issue there? Oops -- didn't see this until just now. Once again, Vivek beat me to the punch :) and much more succinctly than I will ever be able to do. :) P. > > Thanks > Vivek > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753723AbaKFWwx (ORCPT ); Thu, 6 Nov 2014 17:52:53 -0500 Received: from mx1.redhat.com ([209.132.183.28]:45755 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751694AbaKFWws (ORCPT ); Thu, 6 Nov 2014 17:52:48 -0500 Message-ID: <545BFB95.5030706@redhat.com> Date: Thu, 06 Nov 2014 17:52:05 -0500 From: Prarit Bhargava User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20131028 Thunderbird/17.0.10 MIME-Version: 1.0 To: Vivek Goyal CC: David Rientjes , linux-kernel@vger.kernel.org, Jonathan Corbet , Andrew Morton , Rusty Russell , "H. Peter Anvin" , Andi Kleen , Masami Hiramatsu , Fabian Frederick , isimatu.yasuaki@jp.fujitsu.com, jbaron@akamai.com, linux-doc@vger.kernel.org, kexec@lists.infradead.org, linux-api@vger.kernel.org Subject: Re: [PATCH v8] kernel, add panic_on_warn References: <1415187736-16242-1-git-send-email-prarit@redhat.com> <545B733C.6080903@redhat.com> <20141106220731.GA13590@redhat.com> In-Reply-To: <20141106220731.GA13590@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/06/2014 05:07 PM, Vivek Goyal wrote: > On Thu, Nov 06, 2014 at 01:57:36PM -0800, David Rientjes wrote: > > [..] >> You see that doing >> >> if (panic_on_warn) { >> panic_on_warn = 0; >> panic(...); >> } >> >> is racy, I hope. If two threads WARN() at the same time, then there's >> nothing preventing a double panic() because WARN() itself is not >> serialized against anything. So both the current comment and your >> suggested revision comment are bogus. > > panic() is serialized on panic_lock. So I guess it is fine to hit WARN() > on multiple cpus. Do you see an issue there? Oops -- didn't see this until just now. Once again, Vivek beat me to the punch :) and much more succinctly than I will ever be able to do. :) P. > > Thanks > Vivek >