From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754950Ab1LNOuq (ORCPT ); Wed, 14 Dec 2011 09:50:46 -0500 Received: from e5.ny.us.ibm.com ([32.97.182.145]:60415 "EHLO e5.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751129Ab1LNOuo (ORCPT ); Wed, 14 Dec 2011 09:50:44 -0500 Message-ID: <4EE8B78F.9090104@us.ibm.com> Date: Wed, 14 Dec 2011 08:49:51 -0600 From: Anthony Liguori User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.21) Gecko/20110831 Lightning/1.0b2 Thunderbird/3.1.13 MIME-Version: 1.0 To: Avi Kivity CC: Marcelo Tosatti , Eric B Munson , mingo@redhat.com, hpa@zytor.com, arnd@arndb.de, ryanh@linux.vnet.ibm.com, jeremy.fitzhardinge@citrix.com, levinsasha928@gmail.com, Jan Kiszka , kvm@vger.kernel.org, linux-arch@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/5 V5] Avoid soft lockup message when KVM is stopped by host References: <1323116344-17911-1-git-send-email-emunson@mgebm.net> <4EDF7B0D.4060001@redhat.com> <20111214121622.GB18317@amt.cnet> <4EE8B53C.6070502@redhat.com> In-Reply-To: <4EE8B53C.6070502@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit x-cbid: 11121414-5930-0000-0000-0000032AD8D6 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/14/2011 08:39 AM, Avi Kivity wrote: > On 12/14/2011 02:16 PM, Marcelo Tosatti wrote: >>> Having this controlled from userspace means it doesn't work for SIGSTOP >>> or for long scheduling delays. What about doing this automatically >>> based on preempt notifiers? >> >> Long scheduling delays should be considered hangups from the guest >> perspective. > > Why? To the guest it looks like slow hardware, but it will interpret it > as a softlockup. > >> About SIGSTOP, that is a corner case. Unsure if its even properly supported >> by QEMU. > > It works from my experience. We don't adjust vm_clock's offset on SIGSTOP/SIGCONT so while it may appear to work okay, QEMU isn't exhibiting the behavior it is supposed to. Regards, Anthony Liguori >