From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753599AbZICIYv (ORCPT ); Thu, 3 Sep 2009 04:24:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753022AbZICIYv (ORCPT ); Thu, 3 Sep 2009 04:24:51 -0400 Received: from cam-admin0.cambridge.arm.com ([193.131.176.58]:37608 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751290AbZICIYu (ORCPT ); Thu, 3 Sep 2009 04:24:50 -0400 Subject: Re: INFO: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected for kmemleak_lock From: Catalin Marinas To: Eric Paris Cc: linux-kernel@vger.kernel.org In-Reply-To: <1251940799.2425.22.camel@dhcp231-106.rdu.redhat.com> References: <1251838545.2158.67.camel@dhcp231-106.rdu.redhat.com> <1251888848.28251.7.camel@pc1117.cambridge.arm.com> <1251891877.28251.12.camel@pc1117.cambridge.arm.com> <1251940799.2425.22.camel@dhcp231-106.rdu.redhat.com> Content-Type: text/plain Organization: ARM Ltd Date: Thu, 03 Sep 2009 09:24:39 +0100 Message-Id: <1251966279.22485.2.camel@pc1117.cambridge.arm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 03 Sep 2009 08:24:40.0202 (UTC) FILETIME=[FB4426A0:01CA2C6F] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2009-09-02 at 21:19 -0400, Eric Paris wrote: > On Wed, 2009-09-02 at 12:44 +0100, Catalin Marinas wrote: > > On Wed, 2009-09-02 at 11:54 +0100, Catalin Marinas wrote: > > > On Tue, 2009-09-01 at 16:55 -0400, Eric Paris wrote: > > > > I wrote a multithreaded inotify syscall pounder intended to create > > > > files, destroy files, create watches, and destroy watches with the > > > > maximum number of races possible. Instead after letting it run a while > > > > I came upon this! And then my system started to crash in all sorts of > > > > fun and glorious ways (kmem_cache_alloc bugs/panics/whatever) > > > > > > > > -Eric > > > > > > > > [ 2235.913737] ====================================================== > > > > [ 2235.914084] [ INFO: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected ] > > > > [ 2235.914084] 2.6.31-rc8-next-20090901 #64 > > > > [ 2235.914084] ------------------------------------------------------ > > > > [ 2235.914084] syscall_thrash/2516 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire: > > > > [ 2235.914084] (kthread_create_lock){+.+...}, at: [] kthread_create+0x73/0x180 > > > > [ 2235.914084] > > > > [ 2235.914084] and this task is already holding: > > > > [ 2235.914084] (kmemleak_lock){..----}, at: [] create_object+0x161/0x2e0 > > > > [ 2235.914084] which would create a new lock dependency: > > > > [ 2235.914084] (kmemleak_lock){..----} -> (kthread_create_lock){+.+...} > > > > > > Are there other messages from kmemleak printed before that? It looks to > > > me like kmemleak got an exceptional situation (not being able to > > > allocate memory or inserting a pointer into the prio search tree) and it > > > disabled itself. When disabling, it starts a clean-up thread and AFAICT > > > that's the only condition when kmemleak_lock -> kthread_create_lock > > > dependency would be created. > > > > > > I'm not sure whether disabling interrupts around kthread_run in > > > kmemleak_cleanup() would solve the problem. Otherwise, maybe the > > > kmemleak clean-up thread should take a different form or just a thread > > > waiting for a clean-up event (it currently acquires a mutex and cannot > > > be used in interrupt context). > > > > It looks like the kthread_create_lock cannot be acquired in interrupt > > context anyway, so the patch below changes this to a workqueue. > > > > > > kmemleak: Do no create the clean-up thread during kmemleak_disable() > > I'm not going to be able to test as it hasn't happened again. I do > remember seeing messages about kmem leaks being found around the time of > the issue. Although I was working the box as hard as I could, so maybe > I accidentally OOM'd it. Wish there were more I could do to test or > confirm! OK, no problem. Anyway, it found a potential bug in kmemleak, so the patch I posted should fix it (unless anyone spots any issues with the patch). Thanks. -- Catalin