From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752286AbbIOXiZ (ORCPT ); Tue, 15 Sep 2015 19:38:25 -0400 Received: from e32.co.us.ibm.com ([32.97.110.150]:47216 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751558AbbIOXiY (ORCPT ); Tue, 15 Sep 2015 19:38:24 -0400 X-Helo: d03dlp02.boulder.ibm.com X-MailFrom: paulmck@linux.vnet.ibm.com X-RcptTo: linux-kernel@vger.kernel.org Date: Tue, 15 Sep 2015 16:38:18 -0700 From: "Paul E. McKenney" To: Tejun Heo Cc: Christian Borntraeger , Paolo Bonzini , Peter Zijlstra , Ingo Molnar , "linux-kernel@vger.kernel.org >> Linux Kernel Mailing List" , KVM list , Oleg Nesterov Subject: Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Message-ID: <20150915233818.GU4029@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <55F8097A.7000206@de.ibm.com> <20150915130550.GC16853@twins.programming.kicks-ass.net> <55F81EE2.4090708@de.ibm.com> <55F84A6B.1010207@redhat.com> <55F88991.7040406@de.ibm.com> <20150915212622.GC495@htj.duckdns.org> <20150915213830.GR4029@linux.vnet.ibm.com> <20150915222811.GD495@htj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150915222811.GD495@htj.duckdns.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15091523-0005-0000-0000-0000180DEE03 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 15, 2015 at 06:28:11PM -0400, Tejun Heo wrote: > Hello, > > On Tue, Sep 15, 2015 at 02:38:30PM -0700, Paul E. McKenney wrote: > > I did take a shot at adding the rcu_sync stuff during this past merge > > window, but it did not converge quickly enough to make it. It looks > > quite good for the next merge window. There have been changes in most > > of the relevant areas, so probably best to just try them and see which > > works best. > > Heh, I'm having a bit of trouble following. Are you saying that the > changes would be too big for -stable? If so, I'll send out reverts of > the culprit patches and then reapply them for this cycle so that it > can land together with the rcu changes in the next merge window, but > it'd be great to find out whether the rcu changes are enough for the > issue that Christian is seeing to go away. If not, I'll switch to a > different locking scheme and mark those patches w/ stable tag. Well, the decision as to what is too big for -stable is owned by the -stable maintainers, not by me. I am suggesting trying the options and seeing what works best, then working to convince people as needed. Thanx, Paul