From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sergey Senozhatsky Subject: Re: [PATCH 00/50] Add log level to show_stack() Date: Wed, 13 Nov 2019 15:33:34 +0900 Message-ID: <20191113063334.GA147997@google.com> References: <20191108103719.GB175344@google.com> <20191108130447.h3wfgo4efjkto56f@pathway.suse.cz> <20191111012336.GA85185@google.com> <20191111091207.u3lrd6cmumnx4czr@pathway.suse.cz> <20191112044447.GA121272@google.com> <20191112045704.GA138013@google.com> <20191112083509.gmgjpkjffsfaw5lm@pathway.suse.cz> <20191112101229.GA201294@google.com> <20191113012337.GA70781@google.com> <25ff45f0-6420-f660-55a8-637f11ab5ab4@arista.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Edn5IFU3R6j4VJjv3ztj6aOXKuKU2LSfKbAcMlqy9Cs=; b=qwxMZe7FYCvbEG 8naiImeMyj7fVPv2Yayhn+ttya80FCV10L57m+KXfzFlnbiG1bk7y3dfso0xoYsqCaKvsvcI6RTa2 sXrzetn5HHMOalVaiJRDKAPxFC+soyMmJDf6xowRcqJmZqdvIaCAIf0/mMnuNCtbJ0tUrQ24okduj v2HjXgkiOvCoQZUfJSfrXnA9Kqzj+wVjZpOR9+0HAY2TRBzfOpr6XK74wOQbilpKAsVz8AJ4PDmoa 3dqice+DZaW4n7iJ4iu086YmqLbEhfobEENcOHttM2bcecr9h8TxWaq+Syj3oA8aM0jZ4m7QdEefe hDn7aOMHh8C8hglC3P3A==; DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=KPZG4VqXDKJQhwt8QhBKSdwu6zZ1yvGSLXAAovETV8E=; b=U+7/ZvVfxKk+hxsLJDRIKIa9v9E62t1+RHHdRG8fTOKlKCc4Kg8kLlVghoiEvtLKpI pPB/09WWUgNDAvmTd9ZCgUOuDBo7+0/f9WrOXWR2uZQ/aTiznYX6i7YMJNAQqiVBiT9D uNMlkpfHxoC092SA3lqUUmN6Py1jaNvbxPVR7bhPPMcnC5VVTdQfrrvn9g+mwUT9wmS5 IpQo+ozODVnxdup9AaHr+12x4K6wNPJd6H6aHacy3JkNKTrjQ9VPgzg12dvkP1Aua/p8 JdT9N+L+Gr2JhZIIZgVnzKCc48NZMHSHGJjqaFnpF0Bg0opyuGJWVOEoMHo8Jbl+CwGg Qilw== Content-Disposition: inline In-Reply-To: <25ff45f0-6420-f660-55a8-637f11ab5ab4@arista.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-snps-arc" Errors-To: linux-snps-arc-bounces+gla-linux-snps-arc=m.gmane.org@lists.infradead.org To: Dmitry Safonov Cc: Juri Lelli , Sergey Senozhatsky , linux-sh@vger.kernel.org, Catalin Marinas , Ben Segall , Guo Ren , Pavel Machek , Vincent Guittot , Paul Burton , Michael Ellerman , Geert Uytterhoeven , Mel Gorman , Jiri Slaby , Matt Turner , uclinux-h8-devel@lists.sourceforge.jp, Petr Mladek , linux-pm@vger.kernel.org, Heiko Carstens , linux-um@lists.infradead.org, Thomas Gleixner , Dietmar Eggemann , Richard Henderson , Greg Kroah-Hartman , "Rafael J. Wysocki" On (19/11/13 02:25), Dmitry Safonov wrote: > I guess I've pointed that in my point of view price for one-time testing > code is cheaper than adding a new printk feature to swap log levels on > the fly. [..] > I've gone through functions used by sysrq driver and the same changes > introducing log level parameter would be needed for: sched_show_task(), > debug_show_all_locks(), show_regs(), show_state(), show_mem(). Some of > them don't need any platform changes, but at least show_regs() needs. Good points and nice conclusion. Well, here we go. There is a number of generally useful functions that print nice data and where people might want to have better loglevel control (for debugging purposes). show_stack() is just one of them. Patching all those functions, which you have mentioned above, is hardly a fun task to do. Hence the printk() per-CPU per-context loglevel proposition. The code there is not clever or complicated and is meant for debugging purposes only, but with just 3 lines of code one can do some stuff: /* @BTW you can't do this with "%s" KERN_FOO ;P */ + printk_emergency_enter(LOGLEVEL_SCHED); + debug_show_all_locks(); + printk_emergency_exit(); Now... I'm not sure if this whole thing is up to "printk maintainers only". If no one is going to use "emergency printk contexts" then there is no point in having that code in the kernel. -ss 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 X-Spam-Level: X-Spam-Status: No, score=-2.0 required=3.0 tests=DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED,DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27B54C43331 for ; Wed, 13 Nov 2019 06:33:43 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id ED32E222CD for ; Wed, 13 Nov 2019 06:33:42 +0000 (UTC) Authentication-Results: mail.kernel.org; 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Tue, 12 Nov 2019 22:33:38 -0800 (PST) Received: from localhost ([2401:fa00:8f:203:250d:e71d:5a0a:9afe]) by smtp.gmail.com with ESMTPSA id i16sm1209291pfa.184.2019.11.12.22.33.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 Nov 2019 22:33:37 -0800 (PST) Date: Wed, 13 Nov 2019 15:33:34 +0900 From: Sergey Senozhatsky To: Dmitry Safonov Subject: Re: [PATCH 00/50] Add log level to show_stack() Message-ID: <20191113063334.GA147997@google.com> References: <20191108103719.GB175344@google.com> <20191108130447.h3wfgo4efjkto56f@pathway.suse.cz> <20191111012336.GA85185@google.com> <20191111091207.u3lrd6cmumnx4czr@pathway.suse.cz> <20191112044447.GA121272@google.com> <20191112045704.GA138013@google.com> <20191112083509.gmgjpkjffsfaw5lm@pathway.suse.cz> <20191112101229.GA201294@google.com> <20191113012337.GA70781@google.com> <25ff45f0-6420-f660-55a8-637f11ab5ab4@arista.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <25ff45f0-6420-f660-55a8-637f11ab5ab4@arista.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191112_223339_643010_C3BD994E X-CRM114-Status: GOOD ( 12.33 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Juri Lelli , Sergey Senozhatsky , linux-sh@vger.kernel.org, Catalin Marinas , Ben Segall , Guo Ren , Pavel Machek , Vincent Guittot , Paul Burton , Michael Ellerman , Geert Uytterhoeven , Mel Gorman , Jiri Slaby , Matt Turner , uclinux-h8-devel@lists.sourceforge.jp, Petr Mladek , linux-pm@vger.kernel.org, Heiko Carstens , linux-um@lists.infradead.org, Thomas Gleixner , Dietmar Eggemann , Richard Henderson , Greg Kroah-Hartman , "Rafael J. Wysocki" , linux-kernel@vger.kernel.org, Ralf Baechle , Paul Mackerras , Andrew Morton , linux-ia64@vger.kernel.org, Tetsuo Handa , James Hogan , "James E.J. Bottomley" , Max Filippov , Vincent Chen , Ingo Molnar , linux-s390@vger.kernel.org, linux-c6x-dev@linux-c6x.org, Yoshinori Sato , linux-hexagon@vger.kernel.org, Helge Deller , linux-xtensa@linux-xtensa.org, Vasily Gorbik , Aurelien Jacquiot , linux-m68k@lists.linux-m68k.org, Stafford Horne , linux-arm-kernel@lists.infradead.org, Chris Zankel , Tony Luck , Douglas Anderson , Benjamin Herrenschmidt , Dmitry Safonov <0x7f454c46@gmail.com>, Will Deacon , Daniel Thompson , Brian Cain , Christian Borntraeger , kgdb-bugreport@lists.sourceforge.net, linux-snps-arc@lists.infradead.org, Fenghua Yu , Borislav Petkov , Jeff Dike , Steven Rostedt , Ivan Kokshaysky , Greentime Hu , Guan Xuetao , linux-parisc@vger.kernel.org, linux-alpha@vger.kernel.org, Ley Foon Tan , "David S. Miller" , Rich Felker , Len Brown , Peter Zijlstra , "H. Peter Anvin" , sparclinux@vger.kernel.org, linux-riscv@lists.infradead.org, Anton Ivanov , Jonas Bonn , Richard Weinberger , x86@kernel.org, Russell King , clang-built-linux@googlegroups.com, Ingo Molnar , Mark Salter , Albert Ou , Stefan Kristiansson , openrisc@lists.librecores.org, Paul Walmsley , Michal Simek , Vineet Gupta , linux-mips@vger.kernel.org, Sergey Senozhatsky , Palmer Dabbelt , Jason Wessel , nios2-dev@lists.rocketboards.org, linuxppc-dev@lists.ozlabs.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+infradead-linux-riscv=archiver.kernel.org@lists.infradead.org On (19/11/13 02:25), Dmitry Safonov wrote: > I guess I've pointed that in my point of view price for one-time testing > code is cheaper than adding a new printk feature to swap log levels on > the fly. [..] > I've gone through functions used by sysrq driver and the same changes > introducing log level parameter would be needed for: sched_show_task(), > debug_show_all_locks(), show_regs(), show_state(), show_mem(). Some of > them don't need any platform changes, but at least show_regs() needs. Good points and nice conclusion. Well, here we go. There is a number of generally useful functions that print nice data and where people might want to have better loglevel control (for debugging purposes). show_stack() is just one of them. Patching all those functions, which you have mentioned above, is hardly a fun task to do. Hence the printk() per-CPU per-context loglevel proposition. The code there is not clever or complicated and is meant for debugging purposes only, but with just 3 lines of code one can do some stuff: /* @BTW you can't do this with "%s" KERN_FOO ;P */ + printk_emergency_enter(LOGLEVEL_SCHED); + debug_show_all_locks(); + printk_emergency_exit(); Now... I'm not sure if this whole thing is up to "printk maintainers only". If no one is going to use "emergency printk contexts" then there is no point in having that code in the kernel. -ss _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv 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 X-Spam-Level: X-Spam-Status: No, score=-2.0 required=3.0 tests=DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED,DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BF23EC17442 for ; Wed, 13 Nov 2019 06:33:43 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 94158222C1 for ; 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Tue, 12 Nov 2019 22:33:38 -0800 (PST) Received: from localhost ([2401:fa00:8f:203:250d:e71d:5a0a:9afe]) by smtp.gmail.com with ESMTPSA id i16sm1209291pfa.184.2019.11.12.22.33.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 Nov 2019 22:33:37 -0800 (PST) Date: Wed, 13 Nov 2019 15:33:34 +0900 From: Sergey Senozhatsky To: Dmitry Safonov Subject: Re: [PATCH 00/50] Add log level to show_stack() Message-ID: <20191113063334.GA147997@google.com> References: <20191108103719.GB175344@google.com> <20191108130447.h3wfgo4efjkto56f@pathway.suse.cz> <20191111012336.GA85185@google.com> <20191111091207.u3lrd6cmumnx4czr@pathway.suse.cz> <20191112044447.GA121272@google.com> <20191112045704.GA138013@google.com> <20191112083509.gmgjpkjffsfaw5lm@pathway.suse.cz> <20191112101229.GA201294@google.com> <20191113012337.GA70781@google.com> <25ff45f0-6420-f660-55a8-637f11ab5ab4@arista.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <25ff45f0-6420-f660-55a8-637f11ab5ab4@arista.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191112_223339_643010_C3BD994E X-CRM114-Status: GOOD ( 12.33 ) X-BeenThere: linux-snps-arc@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on Synopsys ARC Processors List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Juri Lelli , Sergey Senozhatsky , linux-sh@vger.kernel.org, Catalin Marinas , Ben Segall , Guo Ren , Pavel Machek , Vincent Guittot , Paul Burton , Michael Ellerman , Geert Uytterhoeven , Mel Gorman , Jiri Slaby , Matt Turner , uclinux-h8-devel@lists.sourceforge.jp, Petr Mladek , linux-pm@vger.kernel.org, Heiko Carstens , linux-um@lists.infradead.org, Thomas Gleixner , Dietmar Eggemann , Richard Henderson , Greg Kroah-Hartman , "Rafael J. Wysocki" , linux-kernel@vger.kernel.org, Ralf Baechle , Paul Mackerras , Andrew Morton , linux-ia64@vger.kernel.org, Tetsuo Handa , James Hogan , "James E.J. Bottomley" , Max Filippov , Vincent Chen , Ingo Molnar , linux-s390@vger.kernel.org, linux-c6x-dev@linux-c6x.org, Yoshinori Sato , linux-hexagon@vger.kernel.org, Helge Deller , linux-xtensa@linux-xtensa.org, Vasily Gorbik , Aurelien Jacquiot , linux-m68k@lists.linux-m68k.org, Stafford Horne , linux-arm-kernel@lists.infradead.org, Chris Zankel , Tony Luck , Douglas Anderson , Benjamin Herrenschmidt , Dmitry Safonov <0x7f454c46@gmail.com>, Will Deacon , Daniel Thompson , Brian Cain , Christian Borntraeger , kgdb-bugreport@lists.sourceforge.net, linux-snps-arc@lists.infradead.org, Fenghua Yu , Borislav Petkov , Jeff Dike , Steven Rostedt , Ivan Kokshaysky , Greentime Hu , Guan Xuetao , linux-parisc@vger.kernel.org, linux-alpha@vger.kernel.org, Ley Foon Tan , "David S. Miller" , Rich Felker , Len Brown , Peter Zijlstra , "H. Peter Anvin" , sparclinux@vger.kernel.org, linux-riscv@lists.infradead.org, Anton Ivanov , Jonas Bonn , Richard Weinberger , x86@kernel.org, Russell King , clang-built-linux@googlegroups.com, Ingo Molnar , Mark Salter , Albert Ou , Stefan Kristiansson , openrisc@lists.librecores.org, Paul Walmsley , Michal Simek , Vineet Gupta , linux-mips@vger.kernel.org, Sergey Senozhatsky , Palmer Dabbelt , Jason Wessel , nios2-dev@lists.rocketboards.org, linuxppc-dev@lists.ozlabs.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-snps-arc" Errors-To: linux-snps-arc-bounces+linux-snps-arc=archiver.kernel.org@lists.infradead.org On (19/11/13 02:25), Dmitry Safonov wrote: > I guess I've pointed that in my point of view price for one-time testing > code is cheaper than adding a new printk feature to swap log levels on > the fly. [..] > I've gone through functions used by sysrq driver and the same changes > introducing log level parameter would be needed for: sched_show_task(), > debug_show_all_locks(), show_regs(), show_state(), show_mem(). Some of > them don't need any platform changes, but at least show_regs() needs. Good points and nice conclusion. Well, here we go. There is a number of generally useful functions that print nice data and where people might want to have better loglevel control (for debugging purposes). show_stack() is just one of them. Patching all those functions, which you have mentioned above, is hardly a fun task to do. Hence the printk() per-CPU per-context loglevel proposition. The code there is not clever or complicated and is meant for debugging purposes only, but with just 3 lines of code one can do some stuff: /* @BTW you can't do this with "%s" KERN_FOO ;P */ + printk_emergency_enter(LOGLEVEL_SCHED); + debug_show_all_locks(); + printk_emergency_exit(); Now... I'm not sure if this whole thing is up to "printk maintainers only". If no one is going to use "emergency printk contexts" then there is no point in having that code in the kernel. -ss _______________________________________________ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 13 Nov 2019 15:33:34 +0900 From: Sergey Senozhatsky Subject: Re: [PATCH 00/50] Add log level to show_stack() Message-ID: <20191113063334.GA147997@google.com> References: <20191108103719.GB175344@google.com> <20191108130447.h3wfgo4efjkto56f@pathway.suse.cz> <20191111012336.GA85185@google.com> <20191111091207.u3lrd6cmumnx4czr@pathway.suse.cz> <20191112044447.GA121272@google.com> <20191112045704.GA138013@google.com> <20191112083509.gmgjpkjffsfaw5lm@pathway.suse.cz> <20191112101229.GA201294@google.com> <20191113012337.GA70781@google.com> <25ff45f0-6420-f660-55a8-637f11ab5ab4@arista.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <25ff45f0-6420-f660-55a8-637f11ab5ab4@arista.com> To: Dmitry Safonov Cc: Sergey Senozhatsky , Petr Mladek , Steven Rostedt , linux-kernel@vger.kernel.org, Dmitry Safonov <0x7f454c46@gmail.com>, Andrew Morton , Greg Kroah-Hartman , Ingo Molnar , Jiri Slaby , Sergey Senozhatsky , Tetsuo Handa , Albert Ou , Ben Segall , Dietmar Eggemann , Greentime Hu , Ingo Molnar , James Hogan , Juri Lelli , Mel Gorman , Michal Simek , Palmer Dabbelt , Paul Burton , Paul Walmsley , Peter Zijlstra , Ralf Baechle , Thomas Gleixner , Vincent Chen , Vincent Guittot , Will Deacon , linux-mips@vger.kernel.org, linux-riscv@lists.infradead.org, Ivan Kokshaysky , Matt Turner , Richard Henderson , linux-alpha@vger.kernel.org, Vineet Gupta , linux-snps-arc@lists.infradead.org, Russell King , linux-arm-kernel@lists.infradead.org, clang-built-linux@googlegroups.com, Catalin Marinas , Aurelien Jacquiot , Mark Salter , linux-c6x-dev@linux-c6x.org, Guo Ren , Yoshinori Sato , uclinux-h8-devel@lists.sourceforge.jp, Brian Cain , linux-hexagon@vger.kernel.org, Fenghua Yu , Tony Luck , linux-ia64@vger.kernel.org, Geert Uytterhoeven , linux-m68k@lists.linux-m68k.org, Ley Foon Tan , nios2-dev@lists.rocketboards.org, Jonas Bonn , Stafford Horne , Stefan Kristiansson , openrisc@lists.librecores.org, Helge Deller , "James E.J. Bottomley" , linux-parisc@vger.kernel.org, Benjamin Herrenschmidt , Michael Ellerman , Paul Mackerras , linuxppc-dev@lists.ozlabs.org, Christian Borntraeger , Heiko Carstens , Vasily Gorbik , linux-s390@vger.kernel.org, Rich Felker , linux-sh@vger.kernel.org, "David S. Miller" , sparclinux@vger.kernel.org, Anton Ivanov , Jeff Dike , Richard Weinberger , linux-um@lists.infradead.org, Guan Xuetao , Borislav Petkov , "H. Peter Anvin" , x86@kernel.org, Chris Zankel , Max Filippov , linux-xtensa@linux-xtensa.org, Len Brown , Pavel Machek , "Rafael J. Wysocki" , linux-pm@vger.kernel.org, Daniel Thompson , Douglas Anderson , Jason Wessel , kgdb-bugreport@lists.sourceforge.net List-ID: On (19/11/13 02:25), Dmitry Safonov wrote: > I guess I've pointed that in my point of view price for one-time testing > code is cheaper than adding a new printk feature to swap log levels on > the fly. [..] > I've gone through functions used by sysrq driver and the same changes > introducing log level parameter would be needed for: sched_show_task(), > debug_show_all_locks(), show_regs(), show_state(), show_mem(). Some of > them don't need any platform changes, but at least show_regs() needs. Good points and nice conclusion. Well, here we go. There is a number of generally useful functions that print nice data and where people might want to have better loglevel control (for debugging purposes). show_stack() is just one of them. Patching all those functions, which you have mentioned above, is hardly a fun task to do. Hence the printk() per-CPU per-context loglevel proposition. The code there is not clever or complicated and is meant for debugging purposes only, but with just 3 lines of code one can do some stuff: /* @BTW you can't do this with "%s" KERN_FOO ;P */ + printk_emergency_enter(LOGLEVEL_SCHED); + debug_show_all_locks(); + printk_emergency_exit(); Now... I'm not sure if this whole thing is up to "printk maintainers only". If no one is going to use "emergency printk contexts" then there is no point in having that code in the kernel. -ss From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sergey Senozhatsky Date: Wed, 13 Nov 2019 15:33:34 +0900 Subject: [OpenRISC] [PATCH 00/50] Add log level to show_stack() In-Reply-To: <25ff45f0-6420-f660-55a8-637f11ab5ab4@arista.com> References: <20191108103719.GB175344@google.com> <20191108130447.h3wfgo4efjkto56f@pathway.suse.cz> <20191111012336.GA85185@google.com> <20191111091207.u3lrd6cmumnx4czr@pathway.suse.cz> <20191112044447.GA121272@google.com> <20191112045704.GA138013@google.com> <20191112083509.gmgjpkjffsfaw5lm@pathway.suse.cz> <20191112101229.GA201294@google.com> <20191113012337.GA70781@google.com> <25ff45f0-6420-f660-55a8-637f11ab5ab4@arista.com> Message-ID: <20191113063334.GA147997@google.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: openrisc@lists.librecores.org On (19/11/13 02:25), Dmitry Safonov wrote: > I guess I've pointed that in my point of view price for one-time testing > code is cheaper than adding a new printk feature to swap log levels on > the fly. [..] > I've gone through functions used by sysrq driver and the same changes > introducing log level parameter would be needed for: sched_show_task(), > debug_show_all_locks(), show_regs(), show_state(), show_mem(). Some of > them don't need any platform changes, but at least show_regs() needs. Good points and nice conclusion. Well, here we go. There is a number of generally useful functions that print nice data and where people might want to have better loglevel control (for debugging purposes). show_stack() is just one of them. Patching all those functions, which you have mentioned above, is hardly a fun task to do. Hence the printk() per-CPU per-context loglevel proposition. The code there is not clever or complicated and is meant for debugging purposes only, but with just 3 lines of code one can do some stuff: /* @BTW you can't do this with "%s" KERN_FOO ;P */ + printk_emergency_enter(LOGLEVEL_SCHED); + debug_show_all_locks(); + printk_emergency_exit(); Now... I'm not sure if this whole thing is up to "printk maintainers only". If no one is going to use "emergency printk contexts" then there is no point in having that code in the kernel. -ss 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 X-Spam-Level: X-Spam-Status: No, score=-1.8 required=3.0 tests=DKIM_ADSP_CUSTOM_MED, DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 56555C43331 for ; Wed, 13 Nov 2019 09:47:55 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0390220818 for ; Wed, 13 Nov 2019 09:47:54 +0000 (UTC) Authentication-Results: mail.kernel.org; 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Tue, 12 Nov 2019 22:33:37 -0800 (PST) Date: Wed, 13 Nov 2019 15:33:34 +0900 From: Sergey Senozhatsky To: Dmitry Safonov Subject: Re: [PATCH 00/50] Add log level to show_stack() Message-ID: <20191113063334.GA147997@google.com> References: <20191108103719.GB175344@google.com> <20191108130447.h3wfgo4efjkto56f@pathway.suse.cz> <20191111012336.GA85185@google.com> <20191111091207.u3lrd6cmumnx4czr@pathway.suse.cz> <20191112044447.GA121272@google.com> <20191112045704.GA138013@google.com> <20191112083509.gmgjpkjffsfaw5lm@pathway.suse.cz> <20191112101229.GA201294@google.com> <20191113012337.GA70781@google.com> <25ff45f0-6420-f660-55a8-637f11ab5ab4@arista.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <25ff45f0-6420-f660-55a8-637f11ab5ab4@arista.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Mailman-Approved-At: Wed, 13 Nov 2019 20:43:22 +1100 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: Juri Lelli , Sergey Senozhatsky , linux-sh@vger.kernel.org, Catalin Marinas , Ben Segall , Guo Ren , Pavel Machek , Vincent Guittot , Paul Burton , Geert Uytterhoeven , Mel Gorman , Jiri Slaby , Matt Turner , uclinux-h8-devel@lists.sourceforge.jp, Petr Mladek , linux-pm@vger.kernel.org, Heiko Carstens , linux-um@lists.infradead.org, Thomas Gleixner , Dietmar Eggemann , Richard Henderson , Greg Kroah-Hartman , "Rafael J. Wysocki" , linux-kernel@vger.kernel.org, Ralf Baechle , Paul Mackerras , Andrew Morton , linux-ia64@vger.kernel.org, Tetsuo Handa , James Hogan , "James E.J. Bottomley" , Max Filippov , Vincent Chen , Ingo Molnar , linux-s390@vger.kernel.org, linux-c6x-dev@linux-c6x.org, Yoshinori Sato , linux-hexagon@vger.kernel.org, Helge Deller , linux-xtensa@linux-xtensa.org, Vasily Gorbik , Aurelien Jacquiot , linux-m68k@lists.linux-m68k.org, Stafford Horne , linux-arm-kernel@lists.infradead.org, Chris Zankel , Tony Luck , Douglas Anderson , Dmitry Safonov <0x7f454c46@gmail.com>, Will Deacon , Daniel Thompson , Brian Cain , Christian Borntraeger , kgdb-bugreport@lists.sourceforge.net, linux-snps-arc@lists.infradead.org, Fenghua Yu , Borislav Petkov , Jeff Dike , Steven Rostedt , Ivan Kokshaysky , Greentime Hu , Guan Xuetao , linux-parisc@vger.kernel.org, linux-alpha@vger.kernel.org, Ley Foon Tan , "David S. Miller" , Rich Felker , Len Brown , Peter Zijlstra , "H. Peter Anvin" , sparclinux@vger.kernel.org, linux-riscv@lists.infradead.org, Anton Ivanov , Jonas Bonn , Richard Weinberger , x86@kernel.org, Russell King , clang-built-linux@googlegroups.com, Ingo Molnar , Mark Salter , Albert Ou , Stefan Kristiansson , openrisc@lists.librecores.org, Paul Walmsley , Michal Simek , Vineet Gupta , linux-mips@vger.kernel.org, Sergey Senozhatsky , Palmer Dabbelt , Jason Wessel , nios2-dev@lists.rocketboards.org, linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On (19/11/13 02:25), Dmitry Safonov wrote: > I guess I've pointed that in my point of view price for one-time testing > code is cheaper than adding a new printk feature to swap log levels on > the fly. [..] > I've gone through functions used by sysrq driver and the same changes > introducing log level parameter would be needed for: sched_show_task(), > debug_show_all_locks(), show_regs(), show_state(), show_mem(). Some of > them don't need any platform changes, but at least show_regs() needs. Good points and nice conclusion. Well, here we go. There is a number of generally useful functions that print nice data and where people might want to have better loglevel control (for debugging purposes). show_stack() is just one of them. Patching all those functions, which you have mentioned above, is hardly a fun task to do. Hence the printk() per-CPU per-context loglevel proposition. The code there is not clever or complicated and is meant for debugging purposes only, but with just 3 lines of code one can do some stuff: /* @BTW you can't do this with "%s" KERN_FOO ;P */ + printk_emergency_enter(LOGLEVEL_SCHED); + debug_show_all_locks(); + printk_emergency_exit(); Now... I'm not sure if this whole thing is up to "printk maintainers only". If no one is going to use "emergency printk contexts" then there is no point in having that code in the kernel. -ss