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 0CA00C4332F for ; Tue, 17 May 2022 13:12:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347423AbiEQNMb (ORCPT ); Tue, 17 May 2022 09:12:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52812 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347868AbiEQNLX (ORCPT ); Tue, 17 May 2022 09:11:23 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4F1A21145; Tue, 17 May 2022 06:11:21 -0700 (PDT) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id 0C09D21CDB; 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> Precedence: bulk List-ID: X-Mailing-List: linux-remoteproc@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 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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3F3B1C433F5 for ; Tue, 17 May 2022 13:12:00 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4L2c325Qlbz3byC for ; Tue, 17 May 2022 23:11:58 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=suse.com header.i=@suse.com header.a=rsa-sha256 header.s=susede1 header.b=FE8yzrSt; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=suse.com (client-ip=195.135.220.29; helo=smtp-out2.suse.de; envelope-from=pmladek@suse.com; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=suse.com header.i=@suse.com header.a=rsa-sha256 header.s=susede1 header.b=FE8yzrSt; dkim-atps=neutral Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4L2c2N3mKrz2yn2 for ; Tue, 17 May 2022 23:11:23 +1000 (AEST) 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" 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-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-hyperv@vger.kernel.org, halves@canonical.com, gregkh@linuxfoundation.org, peterz@infradead.org, alejandro.j.jimenez@oracle.com, linux-remoteproc@vger.kernel.org, feng.tang@intel.com, linux-mips@vger.kernel.org, hidehiro.kawai.ez@hitachi.com, sparclinux@vger.kernel.org, will@kernel.org, tglx@linutronix.de, linux-leds@vger.kernel.org, linux-s390@vger.kernel.org, mikelley@microsoft.com, john.ogness@linutronix.de, bhe@redhat.com, corbet@lwn.net, paulmck@kernel.org, fabiomirmar@gmail.com, x86@kernel.org, mingo@redhat.com, bcm-kernel-feedback-list@broadcom.com, xen-devel@lists.xenproject.org, dyoung@redhat.com, vgoyal@redhat.com, linux-xtensa@linux-xtensa.org, dave.hansen@linux.intel.com, keescook@chromium.org, arnd@arndb.de, linux-pm@vger.kernel.org, linux-um@lists.infradead.org, rostedt@goodmis.org, rcu@vger.kernel.org, bp@alien8.de, luto@kernel.org, linux-tegra@vger.kernel.org, openipmi-developer@lists.sourceforge.net, andriy.shevchenko@linux.intel.com, vkuznets@redhat.com, linux-edac@vger.kernel.org, jgross@suse.com, linux-parisc@vger.kernel.org, netdev@vger.kernel.org, kernel@gpiccoli.net, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, stern@rowland.harvard.edu, senozhatsky@chromium.org, d.hatayama@jp.fujitsu.com, mhiramat@kernel.org, kernel-dev@igalia.com, linux-alpha@vger.kernel.org, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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 From mboxrd@z Thu Jan 1 00:00:00 1970 From: Petr Mladek Date: Tue, 17 May 2022 15:11:10 +0200 Subject: [PATCH 14/30] panic: Properly identify the panic event to the notifiers' callbacks In-Reply-To: <244a412c-4589-28d1-bb77-d3648d4f0b12@igalia.com> References: <20220427224924.592546-1-gpiccoli@igalia.com> <20220427224924.592546-15-gpiccoli@igalia.com> <244a412c-4589-28d1-bb77-d3648d4f0b12@igalia.com> Message-ID: List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: kexec@lists.infradead.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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Tue, 17 May 2022 15:11:10 +0200 From: Petr Mladek 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-Disposition: inline In-Reply-To: <244a412c-4589-28d1-bb77-d3648d4f0b12@igalia.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: "linux-um" Errors-To: linux-um-bounces+geert=linux-m68k.org@lists.infradead.org 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 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 _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um From mboxrd@z Thu Jan 1 00:00:00 1970 From: Petr Mladek Subject: Re: [PATCH 14/30] panic: Properly identify the panic event to the notifiers' callbacks Date: Tue, 17 May 2022 15:11:10 +0200 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 Return-path: List-Id: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" 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= Content-Disposition: inline In-Reply-To: <244a412c-4589-28d1-bb77-d3648d4f0b12@igalia.com> Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit 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.ne 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