From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755577Ab2ECRB5 (ORCPT ); Thu, 3 May 2012 13:01:57 -0400 Received: from e37.co.us.ibm.com ([32.97.110.158]:46471 "EHLO e37.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752063Ab2ECRB4 (ORCPT ); Thu, 3 May 2012 13:01:56 -0400 Date: Thu, 3 May 2012 10:01:01 -0700 From: "Paul E. McKenney" To: Sasha Levin Cc: "linux-kernel@vger.kernel.org List" Subject: Re: rcu: BUG on exit_group Message-ID: <20120503170101.GF2592@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20120503154140.GA2592@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12050317-7408-0000-0000-000004B8EF60 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 03, 2012 at 05:55:14PM +0200, Sasha Levin wrote: > On Thu, May 3, 2012 at 5:41 PM, Paul E. McKenney > wrote: > > On Thu, May 03, 2012 at 10:57:19AM +0200, Sasha Levin wrote: > >> Hi Paul, > >> > >> I've hit a BUG similar to the schedule_tail() one when. It happened > >> when I've started fuzzing exit_group() syscalls, and all of the traces > >> are starting with exit_group() (there's a flood of them). > >> > >> I've verified that it indeed BUGs due to the rcu preempt count. > > > > Hello, Sasha, > > > > Which version of -next are you using?  I did some surgery on this > > yesterday based on some bugs Hugh Dickins tracked down, so if you > > are using something older, please move to the current -next. > > I'm using -next from today (3.4.0-rc5-next-20120503-sasha-00002-g09f55ae-dirty). Hmmm... Looking at this more closely, it looks like there really is an attempt to acquire a mutex within an RCU read-side critical section, which is illegal. Could you please bisect this? Thanx, Paul