From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrea Arcangeli Subject: Re: mmu_notifier: Move mmu_notifier_release up to get rid of the invalidat_all() callback Date: Fri, 1 Feb 2008 01:13:55 +0100 Message-ID: <20080201001355.GU7185@v2.random> References: <20080131045750.855008281@sgi.com> <20080131045812.785269387@sgi.com> <20080131123118.GK7185@v2.random> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Peter Zijlstra , linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, steiner-sJ/iWh9BUns@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Avi Kivity , kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, daniel.blueman-xqY44rlHlBpWk0Htik3J/w@public.gmane.org, Robin Holt To: Christoph Lameter Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org On Thu, Jan 31, 2008 at 02:21:58PM -0800, Christoph Lameter wrote: > Is this okay for KVM too? ->release isn't implemented at all in KVM, only the list_del generates complications. I think current code could be already safe through the mm_count pin, becasue KVM relies on the fact anybody pinning through mm_count like KVM does, is forbidden to call unregister and it's forced to wait the auto-disarming when mm_users hits zero, but I feel like something's still wrong if I think that I'm not using call_rcu to free the notifier (OTOH we agreed the list had to be frozen and w/o readers (modulo _release) before _release is called, so if this initial assumption is ok it seems I may be safe w/o call_rcu?). But it's really tricky path. Anyway this is the last of my worries right now, it works perfectly fine with a single user obviously, and the moment KVM threads runs remotely through GRU/XPMEM isn't happening too soon ;) so let's concentrate on the rest first. I can say hlist_del_init doesn't seem to provide any benefit given nobody could possibly decide to call register or unregister after _release run. ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/