From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754343Ab3HPQjH (ORCPT ); Fri, 16 Aug 2013 12:39:07 -0400 Received: from b.ns.miles-group.at ([95.130.255.144]:1660 "EHLO radon.swed.at" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753150Ab3HPQjF (ORCPT ); Fri, 16 Aug 2013 12:39:05 -0400 Message-ID: <520E55A2.9080900@nod.at> Date: Fri, 16 Aug 2013 18:38:58 +0200 From: Richard Weinberger User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130620 Thunderbird/17.0.7 MIME-Version: 1.0 To: Tejun Heo CC: linux-kernel@vger.kernel.org, Jeff Dike , user-mode-linux-devel@lists.sourceforge.net Subject: Re: [PATCH] print_worker_info: Handle pointer with more care References: <1376668606-32354-1-git-send-email-richard@nod.at> <20130816161229.GI2505@htj.dyndns.org> <520E500B.5000408@nod.at> <20130816162844.GJ2505@htj.dyndns.org> In-Reply-To: <20130816162844.GJ2505@htj.dyndns.org> X-Enigmail-Version: 1.5.2 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 16.08.2013 18:28, schrieb Tejun Heo: > On Fri, Aug 16, 2013 at 06:15:07PM +0200, Richard Weinberger wrote: >> On UML I hit the case that pwq is NULL. >> Then we oops at &pwq->wq... > > Hmmm? I'm confused. &pwq->wq is pwq's pointer + wq's offset in pwq. > It doesn't involve dereferencing pwq->wq. Maybe uml isn't > implementing probe_kernel_thread()? Now that I think about it, I'm > not sure how it could. > > cc'ing uml people. Hey, guys, workqueue uses proble_kernel_read() to > print out workqueue related information during oops because those > events are completely asynchronous and workqueue states may not be > consistently accessible. It seems like uml doesn't implement > probe_kernel_read() and tries direct derference of incorrect pointers > leading to its own oops. Maybe uml should check whether the memory is > mapped from probe_kernel_read()? You are already talking to UML people. ;) Anyway, I'll investigate into that. What I see so far is that pwq is NULL after probe_kernel_read(). Thanks, //richard