Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264411AbUFCWWS (ORCPT ); Thu, 3 Jun 2004 18:22:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264414AbUFCWWS (ORCPT ); Thu, 3 Jun 2004 18:22:18 -0400 Received: from mail.ocs.com.au ([202.147.117.210]:21189 "EHLO mail.ocs.com.au") by vger.kernel.org with ESMTP id S264411AbUFCWVa (ORCPT ); Thu, 3 Jun 2004 18:21:30 -0400 X-Mailer: exmh version 2.6.3_20040314 03/14/2004 with nmh-1.0.4 From: Keith Owens To: "Theodore Ts'o" Cc: Oliver Neukum , Dmitry Torokhov , Andrew Morton , linux-kernel@vger.kernel.org, greg@kroah.com, vojtech@suse.cz Subject: Re: [RFC] Changing SysRq - show registers handling In-reply-to: Your message of "Thu, 03 Jun 2004 17:06:01 -0400." <20040603210601.GC6709@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Fri, 04 Jun 2004 08:21:18 +1000 Message-ID: <21192.1086301278@ocs3.ocs.com.au> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1504 Lines: 30 On Thu, 3 Jun 2004 17:06:01 -0400, Theodore Ts'o wrote: >On Thu, Jun 03, 2004 at 09:44:01AM +0200, Oliver Neukum wrote: >> Am Donnerstag, 3. Juni 2004 09:27 schrieb Dmitry Torokhov: >> > I don't like the requirement of SysRq request processing being in hard >> > interrupt handler - that excludes uinput-generated events and precludes >> > moving keyboard handling to a tasklet for example. >> >> SysRq should work even if bottom halfs don't. > >Indeed; one of the times when SysRq-p is used in the field is when the >machine is completely wedged. Sometimes it's the only way to figure >out where the machine is wedged. It would be unfortunate if the >number of cases (when the kernel is four feet in the air and >twitching) where SysRq worked decreases as a result of the proposed >change. KDB has a similar problem, it needs struct pt_regs as a starting point for backtraces and that is not always available. I get around the lack of a pt_regs by using KDB_ENTER() which generates a software interrupt. We could define a software interrupt for SYSRQ_ENTER(key). This would remove all the overhead of saving and tracking pt_regs from the fast paths. The downside is that it needs a software interrupt to be defined for every arch :(. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/