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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <20191106092039.GT4131@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Mailman-Approved-At: Thu, 07 Nov 2019 06:55:51 +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 , 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, 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" Hi Peter, On 11/6/19 9:20 AM, Peter Zijlstra wrote: > On Wed, Nov 06, 2019 at 03:04:51AM +0000, Dmitry Safonov wrote: >> Add log level argument to show_stack(). >> Done in three stages: >> 1. Introducing show_stack_loglvl() for every architecture >> 2. Migrating old users with an explicit log level >> 3. Renaming show_stack_loglvl() into show_stack() >> >> Justification: >> o It's a design mistake to move a business-logic decision >> into platform realization detail. >> o I have currently two patches sets that would benefit from this work: >> Removing console_loglevel jumps in sysrq driver [1] >> Hung task warning before panic [2] - suggested by Tetsuo (but he >> probably didn't realise what it would involve). >> o While doing (1), (2) the backtraces were adjusted to headers >> and other messages for each situation - so there won't be a situation >> when the backtrace is printed, but the headers are missing because >> they have lesser log level (or the reverse). >> o As the result in (2) plays with console_loglevel for kdb are removed. > > I really don't understand that word salad. Why are you doing this? > Sorry, I should have tried to describe better. I'm trying to remove external users of console_loglevel by following reasons: - changing console_loglevel on SMP means that unwanted messages from other CPUs will appear (that have lower log level) - on UMP unwanted messages may appear if the code is preempted while it hasn't set the console_loglevel back to old - rising console_loglevel to print wanted message(s) may not work at all if printk() has being delayed and the console_loglevel is already set back to old value Sysrq driver changes console_loglevel because it needs to print message with a specific log level (the code said userspace relies on this). Kdb changes console_loglevel to print backtrace as the log level depends on architecture realisation. I also have patches in wip those needs to print backtrace with specific loglevel (higher when it's critical, lower when it's notice and shouldn't go to serial console). Besides on local tests I see hits those have headers (messages like "Backtrace: ") without an actual backtrace and the reverse - a backtrace without a reason for it. It's quite annoying and worth addressing by syncing headers log levels to backtraces. Thanks, Dmitry