From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761051Ab2D0SPA (ORCPT ); Fri, 27 Apr 2012 14:15:00 -0400 Received: from e32.co.us.ibm.com ([32.97.110.150]:37167 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761011Ab2D0SO6 (ORCPT ); Fri, 27 Apr 2012 14:14:58 -0400 Date: Fri, 27 Apr 2012 11:14:50 -0700 From: "Paul E. McKenney" To: Sasha Levin Cc: Gleb Natapov , Avi Kivity , Marcelo Tosatti , "linux-kernel@vger.kernel.org List" , kvm@vger.kernel.org Subject: Re: async pf: INFO: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected Message-ID: <20120427181450.GF2534@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20120427152323.GB2419@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12042718-3270-0000-0000-000005E367AC Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 27, 2012 at 08:05:15PM +0200, Sasha Levin wrote: > On Fri, Apr 27, 2012 at 5:23 PM, Paul E. McKenney > wrote: > > > > On Thu, Apr 26, 2012 at 04:50:35PM +0200, Sasha Levin wrote: > > > Hi all. > > > > > > I got a "INFO: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected" > > > warning > > > while running LTP inside a KVM guest using the recent -next kernel. > > > > > > It seems that it was initially originated from rcu_torture_rea(), but I > > > don't think that it's a problem with RCU itself (I'll cc. Paul just in > > > case). RCU torture was indeed configured to run during the testing. > > > > I might be missing something, but I don't see how RCU is involved in > > this one. > > It happened due to a rcutorture thread: > > [ 4248.579019] rcu_torture_rea/1615 [HC0[0]:SC0[0]:HE0:SE1] is trying > to acquire: > [ 4248.579019] (pgd_lock){+.+...}, at: [] pgd_free+0x26/0xa0 > > rcutorture has never triggered anything on my tests up until now, and > is probably not responsible for the actual warning in this case, just > figured I should cc you in case I'm wrong :) No worries! I only responded on the off-chance that everyone else was waiting on me to identify the bug and provide the fix. ;-) Thanx, Paul