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[2620:137:e000::1:18]) by mx.google.com with ESMTPS id e10-20020a656bca000000b003db97293633si1064538pgw.184.2022.05.17.20.37.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 17 May 2022 20:37:38 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:18 as permitted sender) client-ip=2620:137:e000::1:18; Authentication-Results: mx.google.com; dkim=pass header.i=@suse.com header.s=susede1 header.b=FE8yzrSt; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=suse.com Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 29E61644DC; Tue, 17 May 2022 20:26:28 -0700 (PDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347533AbiEQNLt (ORCPT + 99 others); Tue, 17 May 2022 09:11:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52842 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347878AbiEQNLX (ORCPT ); Tue, 17 May 2022 09:11:23 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CF925260; Tue, 17 May 2022 06:11:21 -0700 (PDT) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id 0C7941F88E; Tue, 17 May 2022 13:11:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1652793080; h=from:from:reply-to: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=R3V2DPM1jjc4jD8tVw3U8Rq3S0Maoan+sJ+xup8d8sI=; b=FE8yzrStcygQwANxOmZrJZbOrCy87Ou5DJ3FGcXlGzv/8KcD1Q9vQAYohnpV6O9yl65Qfm zyx0GaYk63CmAg8xlzK3VRV5wlBb3dplZbLwFVDWl++Ff8DNSFdVejZHiQCHUg6G6gVRgz J3YUEPeJCts4dfmVUl5hnzLG7sbV2vU= Received: from suse.cz (unknown [10.100.201.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id D75DF2C141; Tue, 17 May 2022 13:11:17 +0000 (UTC) Date: Tue, 17 May 2022 15:11:10 +0200 From: Petr Mladek To: "Guilherme G. Piccoli" Cc: akpm@linux-foundation.org, bhe@redhat.com, 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-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, d.hatayama@jp.fujitsu.com, dave.hansen@linux.intel.com, dyoung@redhat.com, feng.tang@intel.com, gregkh@linuxfoundation.org, mikelley@microsoft.com, 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 Subject: Re: [PATCH 14/30] panic: Properly identify the panic event to the notifiers' callbacks Message-ID: References: <20220427224924.592546-1-gpiccoli@igalia.com> <20220427224924.592546-15-gpiccoli@igalia.com> <244a412c-4589-28d1-bb77-d3648d4f0b12@igalia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <244a412c-4589-28d1-bb77-d3648d4f0b12@igalia.com> X-Spam-Status: No, score=-2.0 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RDNS_NONE,SPF_HELO_NONE,T_SCC_BODY_TEXT_LINE autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 2022-05-10 13:16:54, Guilherme G. Piccoli wrote: > On 10/05/2022 12:16, Petr Mladek wrote: > > [...] > > Hmm, this looks like a hack. PANIC_UNUSED will never be used. > > All notifiers will be always called with PANIC_NOTIFIER. > > > > The @val parameter is normally used when the same notifier_list > > is used in different situations. > > > > But you are going to use it when the same notifier is used > > in more lists. This is normally distinguished by the @nh > > (atomic_notifier_head) parameter. > > > > IMHO, it is a bad idea. First, it would confuse people because > > it does not follow the original design of the parameters. > > Second, the related code must be touched anyway when > > the notifier is moved into another list so it does not > > help much. > > > > Or do I miss anything, please? > > > > Best Regards, > > Petr > > Hi Petr, thanks for the review. > > I'm not strong attached to this patch, so we could drop it and refactor > the code of next patches to use the @nh as identification - but > personally, I feel this parameter could be used to identify the list > that called such function, in other words, what is the event that > triggered the callback. Some notifiers are even declared with this > parameter called "ev", like the event that triggers the notifier. > > > You mentioned 2 cases: > > (a) Same notifier_list used in different situations; > > (b) Same *notifier callback* used in different lists; > > Mine is case (b), right? Can you show me an example of case (a)? There are many examples of case (a): + module_notify_list: MODULE_STATE_LIVE, /* Normal state. */ MODULE_STATE_COMING, /* Full formed, running module_init. */ MODULE_STATE_GOING, /* Going away. */ MODULE_STATE_UNFORMED, /* Still setting it up. */ + netdev_chain: NETDEV_UP = 1, /* For now you can't veto a device up/down */ NETDEV_DOWN, NETDEV_REBOOT, /* Tell a protocol stack a network interface detected a hardware crash and restarted - we can use this eg to kick tcp sessions once done */ NETDEV_CHANGE, /* Notify device state change */ NETDEV_REGISTER, NETDEV_UNREGISTER, NETDEV_CHANGEMTU, /* notify after mtu change happened */ NETDEV_CHANGEADDR, /* notify after the address change */ NETDEV_PRE_CHANGEADDR, /* notify before the address change */ NETDEV_GOING_DOWN, ... + vt_notifier_list: #define VT_ALLOCATE 0x0001 /* Console got allocated */ #define VT_DEALLOCATE 0x0002 /* Console will be deallocated */ #define VT_WRITE 0x0003 /* A char got output */ #define VT_UPDATE 0x0004 /* A bigger update occurred */ #define VT_PREWRITE 0x0005 /* A char is about to be written to the console */ + die_chain: DIE_OOPS = 1, DIE_INT3, DIE_DEBUG, DIE_PANIC, DIE_NMI, DIE_DIE, DIE_KERNELDEBUG, ... These all call the same list/chain in different situations. The situation is distinguished by @val. > You can see in the following patches (or grep the kernel) that people are using > this identification parameter to determine which kind of OOPS trigger > the callback to condition the execution of the function to specific > cases. Could you please show me some existing code for case (b)? I am not able to find any except in your patches. Anyway, the solution in 16th patch is bad, definitely. hv_die_panic_notify_crash() uses "val" to disinguish both: + "panic_notifier_list" vs "die_chain" + die_val when callen via "die_chain" The API around "die_chain" API is not aware of enum panic_notifier_val and the API using "panic_notifier_list" is not aware of enum die_val. As I said, it is mixing apples and oranges and it is error prone. Best Regards, Petr