From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753688AbbIPOTK (ORCPT ); Wed, 16 Sep 2015 10:19:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48888 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752145AbbIPOTI (ORCPT ); Wed, 16 Sep 2015 10:19:08 -0400 Subject: Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm To: Tejun Heo , Oleg Nesterov References: <55F8097A.7000206@de.ibm.com> <20150915130550.GC16853@twins.programming.kicks-ass.net> <55F81EE2.4090708@de.ibm.com> <55F84A6B.1010207@redhat.com> <20150915173836.GO4029@linux.vnet.ibm.com> <55F92904.4090206@redhat.com> <55F92F04.1040706@de.ibm.com> <55F9326A.9070509@redhat.com> <20150916122249.GA28821@redhat.com> <20150916141630.GA3243@mtj.duckdns.org> Cc: Christian Borntraeger , paulmck@linux.vnet.ibm.com, Peter Zijlstra , Ingo Molnar , "linux-kernel@vger.kernel.org >> Linux Kernel Mailing List" , KVM list From: Paolo Bonzini Message-ID: <55F97A57.8020603@redhat.com> Date: Wed, 16 Sep 2015 16:19:03 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <20150916141630.GA3243@mtj.duckdns.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 16/09/2015 16:16, Tejun Heo wrote: > On Wed, Sep 16, 2015 at 02:22:49PM +0200, Oleg Nesterov wrote: >>> > > If the revert isn't easy, I think backporting rcu_sync is the best bet. >> > >> > I leave this to Paul and Tejun... at least I think this is not v4.2 material. > Will route reverts through cgroup branch. Should be pretty painless. > Nice job on percpu_rwsem. It's so much better than having to come up > with a separate middleground solution. Thanks all for the quick resolution! Paolo