From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 1 Feb 2008 01:13:55 +0100 From: Andrea Arcangeli Subject: Re: mmu_notifier: Move mmu_notifier_release up to get rid of the invalidat_all() callback 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-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: Robin Holt , Avi Kivity , Izik Eidus , kvm-devel@lists.sourceforge.net, Peter Zijlstra , steiner@sgi.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, daniel.blueman@quadrics.com List-ID: 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. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org