From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3vvMy83TtMzDqC4 for ; Fri, 31 Mar 2017 11:36:48 +1100 (AEDT) Date: Fri, 31 Mar 2017 11:36:45 +1100 From: Paul Mackerras To: "Guilherme G. Piccoli" Cc: linuxppc-dev@lists.ozlabs.org, xinhui.pan@linux.vnet.ibm.com, benh@kernel.crashing.org, mpe@ellerman.id.au Subject: Re: [PATCH v4 2/3] powerpc/xmon: drop the nobt option from xmon plus minor fixes Message-ID: <20170331003645.GA12861@fergus.ozlabs.ibm.com> References: <20170322192751.30531-1-gpiccoli@linux.vnet.ibm.com> <20170322192751.30531-3-gpiccoli@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20170322192751.30531-3-gpiccoli@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, Mar 22, 2017 at 04:27:50PM -0300, Guilherme G. Piccoli wrote: > 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! Xmon still can't use a USB keyboard. It's not a question of how well USB keyboards work, it's that having a non-interrupt-driven USB stack with (at least) an OHCI host controller driver and a keyboard driver in xmon is impractical. Paul.