From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422863AbXDXRpM (ORCPT ); Tue, 24 Apr 2007 13:45:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1422881AbXDXRpM (ORCPT ); Tue, 24 Apr 2007 13:45:12 -0400 Received: from smtp1-g19.free.fr ([212.27.42.27]:52399 "EHLO smtp1-g19.free.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1422863AbXDXRpK (ORCPT ); Tue, 24 Apr 2007 13:45:10 -0400 Message-ID: <462E4223.1050109@trango-systems.com> Date: Tue, 24 Apr 2007 19:45:07 +0200 From: LAPLACE Cyprien User-Agent: Icedove 1.5.0.10 (X11/20070329) MIME-Version: 1.0 To: virtualization@lists.linux-foundation.org CC: Linux Kernel , Jeremy Fitzhardinge Subject: SMP lockup in virtualized environment X-Enigmail-Version: 0.94.1.2 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org In a previous mail, Jeremy Fitzhardinge wrote: > The softlockup watchdog is currently a nuisance in a virtual machine, > since the whole system could have the CPU stolen from it for a long > period of time. While it would be unlikely for a guest domain to be > denied timer interrupts for over 10s, it could happen and any > softlockup message would be completely spurious. I wonder how the guest domain can be denied timer interrupts for such a long time ? The only reason I see is that the guest domain is not scheduled at all (host domain or another higher priority guest running). Now in SMP host and guest, what happens if a guest CPU is not scheduled for a while ? An example: in kernel/pid.c:alloc_pid(), if one of the guest CPUs is descheduled when holding the pidmap_lock, what happens to the other guest CPUs who want to alloc/free pids ? Are they blocked too ? -- Cyprien Laplace