From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [103.22.144.67]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3vS7yS0qStzDqHV for ; Tue, 21 Feb 2017 16:16:32 +1100 (AEDT) From: Michael Ellerman To: "Guilherme G. Piccoli" , linuxppc-dev@lists.ozlabs.org Cc: benh@kernel.crashing.org, paulus@samba.org, npiggin@gmail.com, xinhui.pan@linux.vnet.ibm.com, gpiccoli@linux.vnet.ibm.com Subject: Re: [PATCH 2/3] powerpc/xmon: drop the nobt option from xmon plus minor fixes In-Reply-To: <1487290677-7200-3-git-send-email-gpiccoli@linux.vnet.ibm.com> References: <1487290677-7200-1-git-send-email-gpiccoli@linux.vnet.ibm.com> <1487290677-7200-3-git-send-email-gpiccoli@linux.vnet.ibm.com> Date: Tue, 21 Feb 2017 16:16:31 +1100 Message-ID: <87poicm8cw.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , "Guilherme G. Piccoli" writes: > Subject: Re: [PATCH 2/3] powerpc/xmon: drop the nobt option from xmon plus minor fixes In future please use the same version number for all patches of a series. ie. This should include a v2, like the rest of the patches in the series. It confuses the tools to have "v2 1/3" "2/3" "v2 3/3". I realise that might seem a little odd when a patch is new to the series, but the version is the version *of the series*, not the individual patches. For a new patch you can just add after the change log: --- v2: New for v2 of the series. For example. > The xmon parameter nobt was added long time ago, by commit 26c8af5f01df > ("[POWERPC] print backtrace when entering xmon"). The problem that time > was that during a crash in a machine with USB keyboard, xmon wouldn't > respond to commands from the keyboard, so printing the backtrace wouldn't > be possible. > > Idea then was to show automatically the backtrace on xmon crash for the > first time it's invoked (if it recovers, next time xmon won't show > backtrace automatically). The nobt parameter was added _only_ to prevent > this automatic trace show. Seems long time ago USB keyboards didn't work > that well! > > We don't need it anymore, but the feature of auto showing the backtrace > on first crash seems interesting (imagine a case of auto-reboot script), > so this patch keeps the functionality, yet removes the nobt parameter. I'm going to take this as-is, because I want to get it in for v4.11. But I don't think we need the auto back trace logic at all. If anything it's an anti-feature IMHO. Imagine you're debugging a machine and you drop into xmon to check something, then drop out again. Then you go away and leave the box, and it crashes into xmon, but xmon doesn't print a backtrace because you've already been in xmon. Usually you can just get on the console and hit 't', but sometimes the machine crashes so hard that xmon doesn't take input - in which case you now have no backtrace. :sadface: So I'll send a follow-up patch to remove the auto backtrace stuff completely and see if anyone objects. cheers