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 4B541C63697 for ; Wed, 26 Jan 2022 03:11:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236936AbiAZDLI (ORCPT ); Tue, 25 Jan 2022 22:11:08 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:53413 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236915AbiAZDKu (ORCPT ); Tue, 25 Jan 2022 22:10:50 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1643166650; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=C0mi9k2Wv36Blei5iDy0iH94DE1WW0Cz3OmUGyH+6Fc=; b=fH6rv8pQBhPPdBMM+hTJedp0+6Gt0gKm/FHACCgE9lj2hMMXm0cH9YJq8OP+0i+oXK1M/R CS6T/lia1pWQZpxXQTT4d6AWz08dG/83brQt8TwUFjWBMVB7OQ/xFnqrggwG5bAzIh36f1 uo/YYOdoDk5Zb1wvsJcE+gKUwyt2DmQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-255-p6hpPyObNz2Txf5tI2kXmQ-1; Tue, 25 Jan 2022 22:10:46 -0500 X-MC-Unique: p6hpPyObNz2Txf5tI2kXmQ-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C2AEC108088A; Wed, 26 Jan 2022 03:10:43 +0000 (UTC) Received: from localhost (ovpn-12-215.pek2.redhat.com [10.72.12.215]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6ECE4E2C4; Wed, 26 Jan 2022 03:10:42 +0000 (UTC) Date: Wed, 26 Jan 2022 11:10:39 +0800 From: Baoquan He To: "Guilherme G. Piccoli" Cc: Masami Hiramatsu , Petr Mladek , HATAYAMA Daisuke , 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: <20220126031039.GA26064@MiWiFi-R3L-srv> References: <20220108153451.195121-1-gpiccoli@igalia.com> <20220122105514.GA18258@MiWiFi-R3L-srv> <20220123220711.44f1484c9b510eea8cda9c47@kernel.org> <20220124135902.GB8305@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/24/22 at 11:48am, Guilherme G. Piccoli wrote: > On 24/01/2022 10:59, Baoquan He wrote: > > [...] > > About pre_dump, if the dump is crash dump, hope those pre_dump notifiers > > will be executed under conditional check, e.g only if 'crash_kexec_post_notifiers' > > is specified in kernel cmdline. > > Hi Baoquan, based on Petr's suggestion, I think pre_dump would be > responsible for really *non-intrusive/non-risky* tasks and should be > always executed in the panic path (before kdump), regardless of > "crash_kexec_post_notifiers". > > The idea is that the majority of the notifiers would be executed in the > post_dump portion, and for that, we have the > "crash_kexec_post_notifiers" conditional. I also suggest we have > blacklist options (based on function names) for both notifiers, in order > to make kdump issues debug easier. > > Do you agree with that? Feel free to comment with suggestions! > Cheers, I would say "please NO" cautiously. As Petr said, kdump mostly works only if people configure it correctly. That's because we try best to switch to kdump kernel from the fragile panicked kernel immediately. When we try to add anthing before the switching, please consider carefully and ask if that adding is mandatory, otherwise switching into kdump kernel may fail. If the answer is yes, the adding is needed and welcomed. Othewise, any unnecessary action, including any "non-intrusive/non-risky" tasks, would be unwelcomed. Surely, we don't oppose the "non-intrusive/non-risky" or completely "intrusive/risky" action adding before kdump kernel switching, with a conditional limitation. When we handle customers' kdump support, we explicitly declare we only support normal and default kdump operation. If any action which is done before switching into kdump kernel is specified, e.g panic_notifier, panic_print, they need take care of their own kdump failure.