From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <520E55A2.9080900@nod.at> Date: Fri, 16 Aug 2013 18:38:58 +0200 From: Richard Weinberger MIME-Version: 1.0 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> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Subject: Re: [PATCH] print_worker_info: Handle pointer with more care To: Tejun Heo Cc: linux-kernel@vger.kernel.org, Jeff Dike , user-mode-linux-devel@lists.sourceforge.net List-ID: 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