From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752118AbbIOW2R (ORCPT ); Tue, 15 Sep 2015 18:28:17 -0400 Received: from mail-yk0-f170.google.com ([209.85.160.170]:35465 "EHLO mail-yk0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751277AbbIOW2P (ORCPT ); Tue, 15 Sep 2015 18:28:15 -0400 Date: Tue, 15 Sep 2015 18:28:11 -0400 From: Tejun Heo To: "Paul E. McKenney" 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: <20150915222811.GD495@htj.duckdns.org> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150915213830.GR4029@linux.vnet.ibm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Thanks! -- tejun