From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932460Ab2ISQfV (ORCPT ); Wed, 19 Sep 2012 12:35:21 -0400 Received: from mail-ee0-f46.google.com ([74.125.83.46]:42450 "EHLO mail-ee0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753093Ab2ISQfS (ORCPT ); Wed, 19 Sep 2012 12:35:18 -0400 Message-ID: <5059F458.3000407@gmail.com> Date: Wed, 19 Sep 2012 18:35:36 +0200 From: Sasha Levin User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120902 Thunderbird/15.0 MIME-Version: 1.0 To: paulmck@linux.vnet.ibm.com CC: Dave Jones , "linux-kernel@vger.kernel.org" Subject: Re: RCU idle CPU detection is broken in linux-next References: <5050CCE0.4090403@gmail.com> <20120919153934.GB2455@linux.vnet.ibm.com> In-Reply-To: <20120919153934.GB2455@linux.vnet.ibm.com> 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 On 09/19/2012 05:39 PM, Paul E. McKenney wrote: > On Wed, Sep 12, 2012 at 07:56:48PM +0200, Sasha Levin wrote: >> > Hi Paul, >> > >> > While fuzzing using trinity inside a KVM tools guest, I've managed to trigger >> > "RCU used illegally from idle CPU!" warnings several times. >> > >> > There are a bunch of traces which seem to pop exactly at the same time and from >> > different places around the kernel. Here are several of them: > Hello, Sasha, > > OK, interesting. Could you please try reproducing with the diagnostic > patch shown below? Sure - here are the results (btw, it reproduces very easily): [ 13.525119] ================================================ [ 13.527165] [ BUG: lock held when returning to user space! ] [ 13.528752] 3.6.0-rc6-next-20120918-sasha-00002-g190c311-dirty #362 Tainted: GW [ 13.531314] ------------------------------------------------ [ 13.532918] init/1 is leaving the kernel with locks still held! [ 13.534574] 1 lock held by init/1: [ 13.535533] #0: (rcu_idle){.+.+..}, at: [] rcu_eqs_enter_common+0x1a0/0x9a0 I'm basically seeing lots of the above, so I can't even get to the point where I get the previous lockdep warnings.