Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756058Ab1FTXDv (ORCPT ); Mon, 20 Jun 2011 19:03:51 -0400 Received: from smtp-out.google.com ([216.239.44.51]:44600 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755883Ab1FTXDt (ORCPT ); Mon, 20 Jun 2011 19:03:49 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=google.com; s=beta; h=date:from:x-x-sender:to:cc:subject:in-reply-to:message-id :references:user-agent:mime-version:content-type; b=jVVnrppxk7l1PH0cckccyrmszrBIaYyzrwqIq1F35mM5QRmLd++3KsIvoshMIoZ/xK cYNguPWx+vJNnz0BCxlQ== Date: Mon, 20 Jun 2011 16:03:37 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Mandeep Singh Baines cc: Dave Airlie , Andrew Morton , Jesse Barnes , Olof Johansson , linux-fbdev@vger.kernel.org, dri-devel@lists.sf.net, linux-kernel@vger.kernel.org, Chris Fowler Subject: Re: Regression in panic In-Reply-To: Message-ID: References: User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2027 Lines: 51 On Mon, 20 Jun 2011, Mandeep Singh Baines wrote: > Hi Dave, > > I think this change is causing a regression I'm seeing in panic. > Before this change, I'd get a > reboot on panic (we've configured as such). > > With this change, my machine gets wedged if the machine is running in > X when the panic occurs. > > I traced the code flow to this: > > bust_spinlocks(0); > ->unblank_screen(); > ->do_unblank_screen(0); > ->vc->vc_sw->con_blank(vc, 0, 0); > ->fbcon_blank(vc, 0, 0); > ->update_screen(vc); > ->redraw_screen(vc, 0); > ->vc->vc_sw->con_switch(vc); > ->fbcon_switch(vc); > ->ops->update_start(info); > ->bit_update_start(info); > ->fb_pan_display(info, &ops->var); > ->info->fbops->fb_pan_display(var, info); > ->drm_fb_helper_pan_display(var, info); > ->mutex_lock(&dev->mode_config.mutex); *this blocks* > > With this change, there is now a lot going on in the panic path. Stuff > that I'm not sure is safe when panicking. In addition to the > mutex_lock, there is also a del_timer_sync() > now happening in the context of panic(). > > I see this bug with a 2.6.38 kernel but did a quick scan of a newer > kernels and did not see anything that changed in this path so I > suspect its still there. > > Reverting this change fixes the regression. > Chris Fowler reports something similar when running 2.6.38 by inducing a kernel panic via the oom killer -- see http://marc.info/?l=linux-kernel&m=130805985022791. I've added him to the cc so he can participate in the thread and cherry-pick any fixes (last status update was that he was going to be trying 2.6.38.8). -- 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/