From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755890AbZDWQrQ (ORCPT ); Thu, 23 Apr 2009 12:47:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751457AbZDWQq6 (ORCPT ); Thu, 23 Apr 2009 12:46:58 -0400 Received: from victor.provo.novell.com ([137.65.250.26]:37352 "EHLO victor.provo.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751128AbZDWQq5 (ORCPT ); Thu, 23 Apr 2009 12:46:57 -0400 Message-ID: <49F09B78.7000403@novell.com> Date: Thu, 23 Apr 2009 12:46:48 -0400 From: Gregory Haskins User-Agent: Thunderbird 2.0.0.21 (Macintosh/20090302) MIME-Version: 1.0 To: Davide Libenzi CC: kvm@vger.kernel.org, Linux Kernel Mailing List , avi@redhat.com Subject: Re: [KVM PATCH 2/3] eventfd: add a notifier mechanism References: <20090423150910.14094.73708.stgit@dev.haskins.net> <20090423151436.14094.35875.stgit@dev.haskins.net> In-Reply-To: X-Enigmail-Version: 0.95.7 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enigA4C8D3D84102D26A54819969" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigA4C8D3D84102D26A54819969 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Davide Libenzi wrote: > On Thu, 23 Apr 2009, Gregory Haskins wrote: > > =20 >> This allows synchronous notifications to register with the eventfd >> infrastructure. Unlike traditional vfs based eventfd readers, notifie= es >> do not implictly clear the counter on reception. However, the clearin= g >> is primarily important to allowing threads to block waiting for events= >> anyway, so its an acceptable trade-off since blocking doesn't apply to= >> notifiers. >> =20 > > Do you really need to add a notifier? Eventfd already has a wait queue,= =20 > and we support callback-based wakeups, so is there any reason we should= n't=20 > use those and rely on the already existing wakeups? > =20 Well, IIUC the issue is that a wait queue implies that you are in fact waiting...which we may not. :) The target in this particular application with kvm-irqfd is a vcpu context, which *may* be sleeping in something like a HLT, but it also could be in a number of other states such as non-root (guest) mode, it could be running in the kernel, it could be up in userspace, etc. That said: I am not married to the concept that this has to be a notifier callback, but I do want to be able to meet the target application. So if there is some way to do that within the existing wait-queue contstruct, I am open to suggestions. Thanks Davide, -Greg > > > - Davide > > > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > =20 --------------enigA4C8D3D84102D26A54819969 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.11 (Darwin) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEARECAAYFAknwm3kACgkQlOSOBdgZUxkw9wCfTl/cwrwkr0v2j+ZkFLuk2InT ackAoIME19jnipNbGzZF256HaGP0ve8j =oJgO -----END PGP SIGNATURE----- --------------enigA4C8D3D84102D26A54819969--