From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with ESMTP id 951326B007E for ; Wed, 4 Nov 2009 08:15:35 -0500 (EST) Date: Wed, 4 Nov 2009 14:15:33 +0100 From: Andi Kleen Subject: Re: [PATCHv7 3/3] vhost_net: a kernel-level virtio server Message-ID: <20091104131533.GM31511@one.firstfloor.org> References: <20091103172422.GD5591@redhat.com> <878wema6o0.fsf@basil.nowhere.org> <20091104121009.GF8398@redhat.com> <20091104125957.GL31511@one.firstfloor.org> <20091104130828.GC8920@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091104130828.GC8920@redhat.com> Sender: owner-linux-mm@kvack.org To: "Michael S. Tsirkin" Cc: Andi Kleen , netdev@vger.kernel.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, mingo@elte.hu, linux-mm@kvack.org, akpm@linux-foundation.org List-ID: On Wed, Nov 04, 2009 at 03:08:28PM +0200, Michael S. Tsirkin wrote: > On Wed, Nov 04, 2009 at 01:59:57PM +0100, Andi Kleen wrote: > > > Fine? > > > > I cannot say -- are there paths that could drop the device beforehand? > > Do you mean drop the mm reference? No the reference to the device, which owns the mm for you. > > > (as in do you hold a reference to it?) > > By design I think I always have a reference to mm before I use it. > > This works like this: > ioctl SET_OWNER - calls get_task_mm, I think this gets a reference to mm > ioctl SET_BACKEND - checks that SET_OWNER was run, starts virtqueue > ioctl RESET_OWNER - stops virtqueues, drops the reference to mm > file close - stops virtqueues, if we still have it then drops mm > > This is why I think I can call use_mm/unuse_mm while virtqueue is running, > safely. > Makes sense? Do you protect against another thread doing RESET_OWNER in parallel while RESET_OWNER runs? -Andi -- ak@linux.intel.com -- Speaking for myself only. -- 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