From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964829AbWDZTAg (ORCPT ); Wed, 26 Apr 2006 15:00:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964827AbWDZTAg (ORCPT ); Wed, 26 Apr 2006 15:00:36 -0400 Received: from [198.99.130.12] ([198.99.130.12]:34753 "EHLO saraswathi.solana.com") by vger.kernel.org with ESMTP id S964821AbWDZTAf (ORCPT ); Wed, 26 Apr 2006 15:00:35 -0400 Date: Wed, 26 Apr 2006 14:01:10 -0400 From: Jeff Dike To: "Eric W. Biederman" Cc: linux-kernel@vger.kernel.org, user-mode-linux-devel@lists.sourceforge.net Subject: Re: [RFC] PATCH 0/4 - Time virtualization Message-ID: <20060426180110.GB8142@ccure.user-mode-linux.org> References: <200604131719.k3DHJcZG004674@ccure.user-mode-linux.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 19, 2006 at 02:25:00AM -0600, Eric W. Biederman wrote: > That patch should probably be separated, from the rest. > But it looks like a fairly sane idea. Yeah, I'll keep these together for now, but the ptrace one is conceptually different from the rest. > I think you missed a couple essential things to a time namespace. > Timers. The posix timers, in particular. The worst > of those is the monotonic timer. Oops, thanks for pointing that out. > In the case of migration the ugly case to properly handle is the > monotonic timer. That needs an offset yet it is absolutely forbidden > to provide that offset from the inside. So this is the one namespace > that I think is inappropriate to use sys_unshare to create. > We need a system call so that we can specify the minimum or the > starting monotonic time base. For migration, it looks like the container will have to specify the time base at creation so that everything in it will have a consistent view of time if they get moved around. So, maybe it belongs in clone as a "backwards" flag similar to CLONE_NEWNS. Jeff