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 2AB2AC4332F for ; Fri, 20 May 2022 11:24:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348477AbiETLYj (ORCPT ); Fri, 20 May 2022 07:24:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36688 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232303AbiETLYb (ORCPT ); Fri, 20 May 2022 07:24:31 -0400 Received: from fanzine2.igalia.com (fanzine.igalia.com [178.60.130.6]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ECA58B36CE; Fri, 20 May 2022 04:24:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:Content-Type:In-Reply-To:From: References:Cc:To:Subject:MIME-Version:Date:Message-ID:Sender:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=DGPrrkXTp6oI8cbbgByz5QLKv15GNHxUgmjuIwTAy/E=; b=eqnE/suLTpG3xbkMCBtDpxLY3n NIRgLQiaBi0sCvdNCD4AFRLhJwRt1fDLW5HSSGFY7WXFEGFCYXn6Q0dC8gIFph3vTjXA6DvyBiQwz I5PwxVn4HFAkq1g0udGCDh7f8awWYDjllyLtGAcRh6eSoRE6OIuNpAwHVy7SfEQenDYcne2doKiCl jXXzZQlRm486qDYGQtQ0jW8Ms6RtpLdk65Qcz7YJ7/YEdFvKdb+dzF1Re9Q6nwXZnFrLVKgAD5Mwb LfHsy0RngN1antwERG5D/EtoEWfAXqtoLg2k7TzZKasJtkGm7zpf+kH+Fd2GGS1HnQh8pXfJiIePS VAbFF/9w==; Received: from 200-161-159-120.dsl.telesp.net.br ([200.161.159.120] helo=[192.168.1.60]) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_128_GCM:128) (Exim) id 1ns0jj-00Cb4k-Od; Fri, 20 May 2022 13:24:04 +0200 Message-ID: Date: Fri, 20 May 2022 08:23:33 -0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.0 Subject: Re: [PATCH 24/30] panic: Refactor the panic path Content-Language: en-US To: Baoquan He , Petr Mladek Cc: "michael Kelley (LINUX)" , Dave Young , d.hatayama@jp.fujitsu.com, akpm@linux-foundation.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, bcm-kernel-feedback-list@broadcom.com, linuxppc-dev@lists.ozlabs.org, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-edac@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-leds@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-pm@vger.kernel.org, linux-remoteproc@vger.kernel.org, linux-s390@vger.kernel.org, linux-tegra@vger.kernel.org, linux-um@lists.infradead.org, linux-xtensa@linux-xtensa.org, netdev@vger.kernel.org, openipmi-developer@lists.sourceforge.net, rcu@vger.kernel.org, sparclinux@vger.kernel.org, xen-devel@lists.xenproject.org, x86@kernel.org, kernel-dev@igalia.com, kernel@gpiccoli.net, halves@canonical.com, fabiomirmar@gmail.com, alejandro.j.jimenez@oracle.com, andriy.shevchenko@linux.intel.com, arnd@arndb.de, bp@alien8.de, corbet@lwn.net, dave.hansen@linux.intel.com, feng.tang@intel.com, gregkh@linuxfoundation.org, hidehiro.kawai.ez@hitachi.com, jgross@suse.com, john.ogness@linutronix.de, keescook@chromium.org, luto@kernel.org, mhiramat@kernel.org, mingo@redhat.com, paulmck@kernel.org, peterz@infradead.org, rostedt@goodmis.org, senozhatsky@chromium.org, stern@rowland.harvard.edu, tglx@linutronix.de, vgoyal@redhat.com, vkuznets@redhat.com, will@kernel.org References: <20220427224924.592546-1-gpiccoli@igalia.com> <20220427224924.592546-25-gpiccoli@igalia.com> <20220519234502.GA194232@MiWiFi-R3L-srv> From: "Guilherme G. Piccoli" In-Reply-To: <20220519234502.GA194232@MiWiFi-R3L-srv> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 19/05/2022 20:45, Baoquan He wrote: > [...] >> I really appreciate the summary skill you have, to convert complex >> problems in very clear and concise ideas. Thanks for that, very useful! >> I agree with what was summarized above. > > I want to say the similar words to Petr's reviewing comment when I went > through the patches and traced each reviewing sub-thread to try to > catch up. Petr has reivewed this series so carefully and given many > comments I want to ack immediately. > > I agree with most of the suggestions from Petr to this patch, except of > one tiny concern, please see below inline comment. Hi Baoquan, thanks! I'm glad you're also reviewing that =) > [...] > > I like the proposed skeleton of panic() and code style suggested by > Petr very much. About panic_prefer_crash_dump which might need be added, > I hope it has a default value true. This makes crash_dump execute at > first by default just as before, unless people specify > panic_prefer_crash_dump=0|n|off to disable it. Otherwise we need add > panic_prefer_crash_dump=1 in kernel and in our distros to enable kdump, > this is inconsistent with the old behaviour. I'd like to understand better why the crash_kexec() must always be the first thing in your use case. If we keep that behavior, we'll see all sorts of workarounds - see the last patches of this series, Hyper-V and PowerPC folks hardcoded "crash_kexec_post_notifiers" in order to force execution of their relevant notifiers (like the vmbus disconnect, specially in arm64 that has no custom machine_crash_shutdown, or the fadump case in ppc). This led to more risk in kdump. The thing is: with the notifiers' split, we tried to keep only the most relevant/necessary stuff in this first list, things that ultimately should improve kdump reliability or if not, at least not break it. My feeling is that, with this series, we should change the idea/concept that kdump must run first nevertheless, not matter what. We're here trying to accommodate the antagonistic goals of hypervisors that need some clean-up (even for kdump to work) VS. kdump users, that wish a "pristine" system reboot ASAP after the crash. Cheers, Guilherme