From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755268Ab2EGDsL (ORCPT ); Sun, 6 May 2012 23:48:11 -0400 Received: from e3.ny.us.ibm.com ([32.97.182.143]:50009 "EHLO e3.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751476Ab2EGDsJ (ORCPT ); Sun, 6 May 2012 23:48:09 -0400 Date: Sun, 6 May 2012 20:47:49 -0700 From: "Paul E. McKenney" To: Sergey Senozhatsky Cc: Avi Kivity , Marcelo Tosatti , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Dave Jones Subject: Re: possible circular locking dependency Message-ID: <20120507034744.GA3141@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20120503200259.GA3524@swordfish.minsk.epam.com> <4FA63C82.7030309@redhat.com> <20120506164209.GK2470@linux.vnet.ibm.com> <20120506203439.GB3633@swordfish> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120506203439.GB3633@swordfish> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12050703-8974-0000-0000-000008D62A72 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, May 06, 2012 at 11:34:39PM +0300, Sergey Senozhatsky wrote: > On (05/06/12 09:42), Paul E. McKenney wrote: > > On Sun, May 06, 2012 at 11:55:30AM +0300, Avi Kivity wrote: > > > On 05/03/2012 11:02 PM, Sergey Senozhatsky wrote: > > > > Hello, > > > > 3.4-rc5 > > > > > > Whoa. > > > > > > Looks like inconsistent locking between cpufreq and > > > synchronize_srcu_expedited(). kvm triggered this because it is one of > > > the few users of synchronize_srcu_expedited(), but I don't think it is > > > doing anything wrong directly. > > > > > > Dave, Paul? > > > > SRCU hasn't changed much in mainline for quite some time. Holding > > the hotplug mutex across a synchronize_srcu() is a bad idea, though. > > > > However, there is a reworked implementation (courtesy of Lai Jiangshan) > > in -rcu that does not acquire the hotplug mutex. Could you try that out? > > > > Paul, should I try solely -rcu or there are several commits to pick up and apply > on top of -linus tree? If you want the smallest possible change, take the rcu/srcu branch of -rcu. If you want the works, take the rcu/next branch of -rcu. You can find -rcu at: git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git Thanx, Paul