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