Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756930Ab3IKTHW (ORCPT ); Wed, 11 Sep 2013 15:07:22 -0400 Received: from fmailer.gwdg.de ([134.76.11.16]:44138 "EHLO fmailer.gwdg.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751378Ab3IKTHU (ORCPT ); Wed, 11 Sep 2013 15:07:20 -0400 X-Greylist: delayed 2280 seconds by postgrey-1.27 at vger.kernel.org; Wed, 11 Sep 2013 15:07:20 EDT Message-ID: <5230BF5E.9000207@tuebingen.mpg.de> Date: Wed, 11 Sep 2013 21:07:10 +0200 From: Mario Kleiner User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:17.0) Gecko/20130801 Thunderbird/17.0.8 MIME-Version: 1.0 To: Steven Rostedt CC: Peter Hurley , "Luis Claudio R. Goncalves" , linux-rt-users , Thomas Gleixner , Sebastian Andrzej Siewior , Clark Williams , Dave Airlie , LKML , Mario Kleiner Subject: Re: BUG: sleeping function called from invalid context on 3.10.10-rt7 References: <20130911102809.GA31663@uudg.org> <20130911092623.42efd930@gandalf.local.home> <5230895B.5070400@hurleysoftware.com> <5230B673.6090800@tuebingen.mpg.de> <20130911143557.14c1fe6a@gandalf.local.home> In-Reply-To: <20130911143557.14c1fe6a@gandalf.local.home> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1879 Lines: 43 On 11.09.13 20:35, Steven Rostedt wrote: > On Wed, 11 Sep 2013 20:29:07 +0200 > Mario Kleiner wrote: > >> That said, maybe preempt_disable is no longer the optimal choice there >> and there's some better way to achieve good protection against >> interruptions of that bit of code? My knowledge here is a bit rusty, and >> the intel kms drivers and rt stuff has changed quite a bit. > > If you set your code to a higher priority than other tasks (and > interrupts) than it wont be preempted there. Unless of course it blocks > on a lock, but even then, priority inheritance will take place and it > still should be rather quick. (unless the holder of the lock is doing > that strange polling). > > -- Steve > Right, on a rt kernel. But that creates the problem of not very computer savvy users (psychologists and biologists mostly) somehow having to choose proper priorities for gpu interrupt threads and for the x-server/wayland/..., and not much protection on a non-rt kernel? preempt_disable() a few years ago looked like a good "plug and play" default solution, because the ->get_crtc_scanoutpos() function was supposed to have a very low and bounded execution time. At the time we wrote the patches for intel/radeon/nouveau, that was the case. Typical execution time (= preempt off time) was like 1-4 usecs, even on very low end hardware. Seems that at least intel's kms driver does a lot of things now, which can sleep and spin inside that section? I tried to follow the posted stack trace, but got lost somewhere around the i915_read32 code and power management stuff... -mario -- 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/