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Received: from shell.armlinux.org.uk ([2001:4d48:ad52:3201:5054:ff:fe00:4ec]:52746) by pandora.armlinux.org.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1iSUgS-00085H-Vb; Wed, 06 Nov 2019 23:25:53 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1iSUfp-0004Pa-1s; Wed, 06 Nov 2019 23:25:13 +0000 Date: Wed, 6 Nov 2019 23:25:13 +0000 From: Russell King - ARM Linux admin To: Peter Zijlstra Subject: Re: [PATCH 00/50] Add log level to show_stack() Message-ID: <20191106232512.GU25745@shell.armlinux.org.uk> References: <20191106030542.868541-1-dima@arista.com> <20191106092039.GT4131@hirez.programming.kicks-ass.net> <10db6fa1-5b17-ebe6-09e0-6335e09e4db8@arista.com> <20191106203440.GH3079@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20191106203440.GH3079@worktop.programming.kicks-ass.net> 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-20191106_152815_574233_47586EE9 X-CRM114-Status: GOOD ( 12.06 ) 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 , linux-sh@vger.kernel.org, Catalin Marinas , Ben Segall , Guo Ren , Pavel Machek , Vincent Guittot , Paul Burton , Dmitry Safonov , Michael Ellerman , Geert Uytterhoeven , Mel Gorman , Jiri Slaby , Matt Turner , uclinux-h8-devel@lists.sourceforge.jp, Len Brown , 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 , Petr Mladek , "H. Peter Anvin" , sparclinux@vger.kernel.org, linux-riscv@lists.infradead.org, Anton Ivanov , Jonas Bonn , Richard Weinberger , x86@kernel.org, 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 Wed, Nov 06, 2019 at 09:34:40PM +0100, Peter Zijlstra wrote: > I suppose I'm surprised there are backtraces that are not important. > Either badness happened and it needs printing, or the user asked for it > and it needs printing. Or utterly meaningless. > Perhaps we should be removing backtraces if they're not important > instead of allowing to print them as lower loglevels? Definitely! WARN_ON() is well overused - and as is typical, used without much thought. Bound to happen after Linus got shirty about BUG_ON() being over used. Everyone just grabbed the next nearest thing to assert(). As a kind of example, I've recently come across one WARN_ON() in a driver subsystem (that shall remain nameless at the moment) which very likely has multiple different devices on a platform. The WARN_ON() triggers as a result of a problem with the hardware, but because it's a WARN_ON(), you've no idea which device has a problem. The backtrace is mostly meaningless. So you know that a problem has occurred, but the kernel prints *useless* backtrace to let you know, and totally omits the *useful* information. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up _______________________________________________ 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_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 E755AFC6196 for ; 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charset=us-ascii Content-Disposition: inline In-Reply-To: <20191106203440.GH3079@worktop.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) X-Mailman-Approved-At: Thu, 07 Nov 2019 11:50:16 +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 , linux-sh@vger.kernel.org, Catalin Marinas , Ben Segall , Guo Ren , Pavel Machek , Vincent Guittot , Paul Burton , Dmitry Safonov , Geert Uytterhoeven , Mel Gorman , Jiri Slaby , Matt Turner , uclinux-h8-devel@lists.sourceforge.jp, Len Brown , 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 , Petr Mladek , "H. Peter Anvin" , sparclinux@vger.kernel.org, linux-riscv@lists.infradead.org, Anton Ivanov , Jonas Bonn , Richard Weinberger , x86@kernel.org, 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 Wed, Nov 06, 2019 at 09:34:40PM +0100, Peter Zijlstra wrote: > I suppose I'm surprised there are backtraces that are not important. > Either badness happened and it needs printing, or the user asked for it > and it needs printing. Or utterly meaningless. > Perhaps we should be removing backtraces if they're not important > instead of allowing to print them as lower loglevels? Definitely! WARN_ON() is well overused - and as is typical, used without much thought. Bound to happen after Linus got shirty about BUG_ON() being over used. Everyone just grabbed the next nearest thing to assert(). As a kind of example, I've recently come across one WARN_ON() in a driver subsystem (that shall remain nameless at the moment) which very likely has multiple different devices on a platform. The WARN_ON() triggers as a result of a problem with the hardware, but because it's a WARN_ON(), you've no idea which device has a problem. The backtrace is mostly meaningless. So you know that a problem has occurred, but the kernel prints *useless* backtrace to let you know, and totally omits the *useful* information. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up 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=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 C737FFC6194 for ; Wed, 6 Nov 2019 23:28:20 +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 9810B20663 for ; 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bh=PRxpis2yYVwo9kDaUSfGCl5VFlJxyHbhU0YR7G7gbJ8=; b=iy2paYFVbfDDxvP/gOAeR2zl0 YOZEPL3WjHOmVg+0OQahNkJkI83R2voT2LINyyq/NpOQgJ8XbP653WAnOCKJeMd3FQfk1r00D1g6Z fp0OZxAP4Vl3Ld3lf2vsPvJVAaYSvfV/oRelynTl2M99Xzch5Yo0n9rKkDRrpqI+VDj8uG0IE0Mwu DLXZUR9cXBF6yhsVU66Hv9Zw3qb9D4TtgACKhdNRerRuquMvaCXNfaGPMRzGBVS3f+JaE6Gz3Dc5B ZjnPN/i029uWQPyVkPtoGc8KSHKL1/41r92P9256aLhtNWmorZhciQ3YdFO8welchayVt2ute4n7E rzURiZTZA==; Received: from shell.armlinux.org.uk ([2001:4d48:ad52:3201:5054:ff:fe00:4ec]:52746) by pandora.armlinux.org.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1iSUgS-00085H-Vb; Wed, 06 Nov 2019 23:25:53 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1iSUfp-0004Pa-1s; Wed, 06 Nov 2019 23:25:13 +0000 Date: Wed, 6 Nov 2019 23:25:13 +0000 From: Russell King - ARM Linux admin To: Peter Zijlstra Subject: Re: [PATCH 00/50] Add log level to show_stack() Message-ID: <20191106232512.GU25745@shell.armlinux.org.uk> References: <20191106030542.868541-1-dima@arista.com> <20191106092039.GT4131@hirez.programming.kicks-ass.net> <10db6fa1-5b17-ebe6-09e0-6335e09e4db8@arista.com> <20191106203440.GH3079@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20191106203440.GH3079@worktop.programming.kicks-ass.net> 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-20191106_152815_574233_47586EE9 X-CRM114-Status: GOOD ( 12.06 ) 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 , linux-sh@vger.kernel.org, Catalin Marinas , Ben Segall , Guo Ren , Pavel Machek , Vincent Guittot , Paul Burton , Dmitry Safonov , Michael Ellerman , Geert Uytterhoeven , Mel Gorman , Jiri Slaby , Matt Turner , uclinux-h8-devel@lists.sourceforge.jp, Len Brown , 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 , Petr Mladek , "H. Peter Anvin" , sparclinux@vger.kernel.org, linux-riscv@lists.infradead.org, Anton Ivanov , Jonas Bonn , Richard Weinberger , x86@kernel.org, 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 Wed, Nov 06, 2019 at 09:34:40PM +0100, Peter Zijlstra wrote: > I suppose I'm surprised there are backtraces that are not important. > Either badness happened and it needs printing, or the user asked for it > and it needs printing. Or utterly meaningless. > Perhaps we should be removing backtraces if they're not important > instead of allowing to print them as lower loglevels? Definitely! WARN_ON() is well overused - and as is typical, used without much thought. Bound to happen after Linus got shirty about BUG_ON() being over used. Everyone just grabbed the next nearest thing to assert(). As a kind of example, I've recently come across one WARN_ON() in a driver subsystem (that shall remain nameless at the moment) which very likely has multiple different devices on a platform. The WARN_ON() triggers as a result of a problem with the hardware, but because it's a WARN_ON(), you've no idea which device has a problem. The backtrace is mostly meaningless. So you know that a problem has occurred, but the kernel prints *useless* backtrace to let you know, and totally omits the *useful* information. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up _______________________________________________ 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 From: Russell King - ARM Linux admin Date: Wed, 6 Nov 2019 23:25:13 +0000 Subject: [OpenRISC] [PATCH 00/50] Add log level to show_stack() In-Reply-To: <20191106203440.GH3079@worktop.programming.kicks-ass.net> References: <20191106030542.868541-1-dima@arista.com> <20191106092039.GT4131@hirez.programming.kicks-ass.net> <10db6fa1-5b17-ebe6-09e0-6335e09e4db8@arista.com> <20191106203440.GH3079@worktop.programming.kicks-ass.net> Message-ID: <20191106232512.GU25745@shell.armlinux.org.uk> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: openrisc@lists.librecores.org On Wed, Nov 06, 2019 at 09:34:40PM +0100, Peter Zijlstra wrote: > I suppose I'm surprised there are backtraces that are not important. > Either badness happened and it needs printing, or the user asked for it > and it needs printing. Or utterly meaningless. > Perhaps we should be removing backtraces if they're not important > instead of allowing to print them as lower loglevels? Definitely! WARN_ON() is well overused - and as is typical, used without much thought. Bound to happen after Linus got shirty about BUG_ON() being over used. Everyone just grabbed the next nearest thing to assert(). As a kind of example, I've recently come across one WARN_ON() in a driver subsystem (that shall remain nameless at the moment) which very likely has multiple different devices on a platform. The WARN_ON() triggers as a result of a problem with the hardware, but because it's a WARN_ON(), you've no idea which device has a problem. The backtrace is mostly meaningless. So you know that a problem has occurred, but the kernel prints *useless* backtrace to let you know, and totally omits the *useful* information. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 6 Nov 2019 23:25:13 +0000 From: Russell King - ARM Linux admin Subject: Re: [PATCH 00/50] Add log level to show_stack() Message-ID: <20191106232512.GU25745@shell.armlinux.org.uk> References: <20191106030542.868541-1-dima@arista.com> <20191106092039.GT4131@hirez.programming.kicks-ass.net> <10db6fa1-5b17-ebe6-09e0-6335e09e4db8@arista.com> <20191106203440.GH3079@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20191106203440.GH3079@worktop.programming.kicks-ass.net> 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: Peter Zijlstra Cc: Juri Lelli , linux-sh@vger.kernel.org, Catalin Marinas , Ben Segall , Guo Ren , Pavel Machek , Vincent Guittot , Paul Burton , Dmitry Safonov , Michael Ellerman , Geert Uytterhoeven , Mel Gorman , Jiri Slaby , Matt Turner , uclinux-h8-devel@lists.sourceforge.jp, Len Brown , 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 , Petr Mladek , "H. Peter Anvin" , sparclinux@vger.kernel.org, linux-riscv@lists.infradead.org, Anton Ivanov , Jonas Bonn , Richard Weinberger , x86@kernel.org, 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 On Wed, Nov 06, 2019 at 09:34:40PM +0100, Peter Zijlstra wrote: > I suppose I'm surprised there are backtraces that are not important. > Either badness happened and it needs printing, or the user asked for it > and it needs printing. Or utterly meaningless. > Perhaps we should be removing backtraces if they're not important > instead of allowing to print them as lower loglevels? Definitely! WARN_ON() is well overused - and as is typical, used without much thought. Bound to happen after Linus got shirty about BUG_ON() being over used. Everyone just grabbed the next nearest thing to assert(). As a kind of example, I've recently come across one WARN_ON() in a driver subsystem (that shall remain nameless at the moment) which very likely has multiple different devices on a platform. The WARN_ON() triggers as a result of a problem with the hardware, but because it's a WARN_ON(), you've no idea which device has a problem. The backtrace is mostly meaningless. So you know that a problem has occurred, but the kernel prints *useless* backtrace to let you know, and totally omits the *useful* information. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up _______________________________________________ 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: Russell King - ARM Linux admin Subject: Re: [PATCH 00/50] Add log level to show_stack() Date: Wed, 6 Nov 2019 23:25:13 +0000 Message-ID: <20191106232512.GU25745@shell.armlinux.org.uk> References: <20191106030542.868541-1-dima@arista.com> <20191106092039.GT4131@hirez.programming.kicks-ass.net> <10db6fa1-5b17-ebe6-09e0-6335e09e4db8@arista.com> <20191106203440.GH3079@worktop.programming.kicks-ass.net> 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=4qMxNANvD2mKx5rRvKwF+D2iZps98DMNuo9E1FfjoHc=; b=m/SDtYG120STwL oSppZHrLi9PCbeMCjrMEoLV4xZFkfwfbdF31qsXGuaX+qUMHLHxBAoW/o2JbTWJSfgTzLoPtaADpI s00bZl56+Mp7jPdWIdK0MeMfX8rlH9toqVdoWwhA5azI4DsIy1dp0bt2xAlUgeuVn425/je8CVzDr qGGc89vl2N169sXShYSaeWZ3zxtFdcQBn1HvihOcMIgsPGbnkTBScRWdVH3w6pAifpCxyO+WdAZUi 8Z9EGfMrB/nKgL+8NghfXfU+nbb5my+wSeC6a/mqVcE7ETdL9qcTYhm2RZfrt3BYXLPjPxkLnclsm C+KhxFHfhgOYEJcuTHnw==; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding: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=PRxpis2yYVwo9kDaUSfGCl5VFlJxyHbhU0YR7G7gbJ8=; b=iy2paYFVbfDDxvP/gOAeR2zl0 YOZEPL3WjHOmVg+0OQahNkJkI83R2voT2LINyyq/NpOQgJ8XbP653WAnOCKJeMd3FQfk1r00D1g6Z fp0OZxAP4Vl3Ld3lf2vsPvJVAaYSvfV/oRelynTl2M99Xzch5Yo0n9rKkDRrpqI+VDj8uG0IE0Mwu DLXZUR9cXBF6yhsVU66Hv9Zw3qb9D4TtgACKhdNRerRuquMvaCXNfaGPMRzGBVS3f+JaE6Gz3Dc5B ZjnPN/i029uWQPyVkPtoGc8KSHKL1/41r92P9256aLhtNWmorZhciQ3YdFO8welchayVt2ute4n7E rzURiZTZA==; Content-Disposition: inline In-Reply-To: <20191106203440.GH3079@worktop.programming.kicks-ass.net> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-riscv" Errors-To: linux-riscv-bounces+glpr-linux-riscv=m.gmane.org@lists.infradead.org To: Peter Zijlstra Cc: Juri Lelli , linux-sh@vger.kernel.org, Catalin Marinas , Ben Segall , Guo Ren , Pavel Machek , Vincent Guittot , Paul Burton , Dmitry Safonov , Michael Ellerman , Geert Uytterhoeven , Mel Gorman , Jiri Slaby , Matt Turner , uclinux-h8-devel@lists.sourceforge.jp, Len Brown , 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-kerne On Wed, Nov 06, 2019 at 09:34:40PM +0100, Peter Zijlstra wrote: > I suppose I'm surprised there are backtraces that are not important. > Either badness happened and it needs printing, or the user asked for it > and it needs printing. Or utterly meaningless. > Perhaps we should be removing backtraces if they're not important > instead of allowing to print them as lower loglevels? Definitely! WARN_ON() is well overused - and as is typical, used without much thought. Bound to happen after Linus got shirty about BUG_ON() being over used. Everyone just grabbed the next nearest thing to assert(). As a kind of example, I've recently come across one WARN_ON() in a driver subsystem (that shall remain nameless at the moment) which very likely has multiple different devices on a platform. The WARN_ON() triggers as a result of a problem with the hardware, but because it's a WARN_ON(), you've no idea which device has a problem. The backtrace is mostly meaningless. So you know that a problem has occurred, but the kernel prints *useless* backtrace to let you know, and totally omits the *useful* information. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up