From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 172DFC433EF for ; Sun, 23 Jan 2022 13:07:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236402AbiAWNHY (ORCPT ); Sun, 23 Jan 2022 08:07:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33976 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232822AbiAWNHV (ORCPT ); Sun, 23 Jan 2022 08:07:21 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D7DCDC06173B; Sun, 23 Jan 2022 05:07:20 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 626C060C3E; Sun, 23 Jan 2022 13:07:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 34E0EC340E2; Sun, 23 Jan 2022 13:07:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1642943239; bh=BxRaDiPr6cRH66AV0Yija/RCD3QlZ9vVEudJ4scQQsI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=hwgKvPwuYEaOu2BKbuEUJ7Kp32LDYAg8qNugAprE0WJ0/8mYe6+K5qR7pBs62wekG HtDv8yrJuf4JYknNquvuFYt9dZysD7QlxpPy5OzipBYcXuOiNGtzMuRh0+dFy0vmla E/Ody41EjcVaCjtkhtnx1aLos+tftHIBAsAKUkYsejbilA2B3bF/UDovsj71oSbw1E eucnld3DDKIDsLRjTUB6Xg+vinQ8hZKdJjqtBtLJf54obVQBGUPVd/+ZvgT1qfFQnL v/+9nyfG33d7MU5XqUSUxGyT6lYJzfmoctDjd2znIrPLdMv6eD4WaOm+3PnspeWHsA c1cmlGcQOTG3A== Date: Sun, 23 Jan 2022 22:07:11 +0900 From: Masami Hiramatsu To: Baoquan He Cc: "Guilherme G. Piccoli" , HATAYAMA Daisuke , Petr Mladek , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, dyoung@redhat.com, linux-doc@vger.kernel.org, vgoyal@redhat.com, stern@rowland.harvard.edu, akpm@linux-foundation.org, andriy.shevchenko@linux.intel.com, corbet@lwn.net, halves@canonical.com, kernel@gpiccoli.net, Will Deacon , Kees Cook , Steven Rostedt , Hidehiro Kawai , Vitaly Kuznetsov , John Ogness , "Paul E. McKenney" , Peter Zijlstra , Juergen Gross , mikelley@microsoft.com Subject: Re: [PATCH V4] notifier/panic: Introduce panic_notifier_filter Message-Id: <20220123220711.44f1484c9b510eea8cda9c47@kernel.org> In-Reply-To: <20220122105514.GA18258@MiWiFi-R3L-srv> References: <20220108153451.195121-1-gpiccoli@igalia.com> <20220122105514.GA18258@MiWiFi-R3L-srv> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 22 Jan 2022 18:55:14 +0800 Baoquan He wrote: > On 01/21/22 at 05:31pm, Guilherme G. Piccoli wrote: > ...... > > > IMHO, the right solution is to split the callbacks into 2 or more > > > notifier list. Then we might rework panic() to do: > > > > > > void panic(void) > > > { > > > [...] > > > > > > /* stop watchdogs + extra info */ > > > atomic_notifier_call_chain(&panic_disable_watchdogs_notifier_list, 0, buf); > > > atomic_notifier_call_chain(&panic_info_notifier_list, 0, buf); > > > panic_print_sys_info(); > > > > > > /* crash_kexec + kmsg_dump in configurable order */ > > > if (!_crash_kexec_post_kmsg_dump) { > > > __crash_kexec(NULL); > > > smp_send_stop(); > > > } else { > > > crash_smp_send_stop(); > > > } > > > > > > kmsg_dump(); > > > if (_crash_kexec_post_kmsg_dump) > > > __crash_kexec(NULL); > > > > > > /* infinite loop or reboot */ > > > atomic_notifier_call_chain(&panic_hypervisor_notifier_list, 0, buf); > > > atomic_notifier_call_chain(&panic_rest_notifier_list, 0, buf); > > > > > > console_flush_on_panic(CONSOLE_FLUSH_PENDING); > > > [...] > > > Two notifier lists might be enough in the above scenario. I would call > > > them: > > > > > > panic_pre_dump_notifier_list > > > panic_post_dump_notifier_list > > > > > > > > > It is a real solution that will help everyone. It is more complicated now > > > but it will makes things much easier in the long term. And it might be done > > > step by step: > > > > > > 1. introduce the two notifier lists > > > 2. convert all users: one by one > > > 3. remove the original notifier list when there is no user > > > > That's a great idea! I'm into it, if we have a consensus. The thing that > > scares me most here is that this is a big change and consumes time to > > implement - I'd not risk such time if somebody is really against that. > > So, let's see more opinions, maybe the kdump maintainers have good input. > > I am fine with it. As long as thing is made clear, glad to see code is > refactored to be more understandable and improved. Earlier, during several > rounds of discussion between you and Petr, seveal pitfalls have been > pointed out and avoided. > > Meanwhile, I would suggest Masa and HATAYAMA to help give input about > panic_notifier usage and refactory. AFAIK, they contributed code and use > panic_notifier in their product or environment a lot, that will be very > helpful to get the first hand information from them. > > Hi Masa, HATAYANA, > > Any comment on this? (Please ignore this if it's not in your care.) No, that looks good idea to me. BTW, the 'dump' in the new notifieers means both kmsg_dump and crash dump, right? Thank you, -- Masami Hiramatsu