From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756707Ab2ISRZk (ORCPT ); Wed, 19 Sep 2012 13:25:40 -0400 Received: from e39.co.us.ibm.com ([32.97.110.160]:35045 "EHLO e39.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753954Ab2ISRZi (ORCPT ); Wed, 19 Sep 2012 13:25:38 -0400 Date: Wed, 19 Sep 2012 10:06:48 -0700 From: "Paul E. McKenney" To: Sasha Levin Cc: Dave Jones , "linux-kernel@vger.kernel.org" Subject: Re: RCU idle CPU detection is broken in linux-next Message-ID: <20120919170648.GF2455@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <5050CCE0.4090403@gmail.com> <20120919153934.GB2455@linux.vnet.ibm.com> <5059F458.3000407@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5059F458.3000407@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12091917-4242-0000-0000-000002F48D9F Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 19, 2012 at 06:35:36PM +0200, Sasha Levin wrote: > 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. OK, that diagnostic patch was unhelpful. Back to the drawing board... Thanx, Paul