From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755399Ab2GQOJj (ORCPT ); Tue, 17 Jul 2012 10:09:39 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55523 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754762Ab2GQOJi (ORCPT ); Tue, 17 Jul 2012 10:09:38 -0400 Date: Tue, 17 Jul 2012 17:10:02 +0300 From: "Michael S. Tsirkin" To: Alex Williamson Cc: avi@redhat.com, gleb@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, jan.kiszka@siemens.com Subject: Re: [PATCH v5 2/4] kvm: KVM_EOIFD, an eventfd for EOIs Message-ID: <20120717141002.GC10822@redhat.com> References: <20120716202711.1752.71007.stgit@bling.home> <20120716203353.1752.19127.stgit@bling.home> <20120717102139.GG7949@redhat.com> <1342533556.3229.7.camel@ul30vt> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1342533556.3229.7.camel@ul30vt> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 17, 2012 at 07:59:16AM -0600, Alex Williamson wrote: > On Tue, 2012-07-17 at 13:21 +0300, Michael S. Tsirkin wrote: > > On Mon, Jul 16, 2012 at 02:33:55PM -0600, Alex Williamson wrote: > > > + if (args->flags & KVM_EOIFD_FLAG_LEVEL_IRQFD) { > > > + struct _irqfd *irqfd = _irqfd_fdget_lock(kvm, args->irqfd); > > > + if (IS_ERR(irqfd)) { > > > + ret = PTR_ERR(irqfd); > > > + goto fail; > > > + } > > > + > > > + gsi = irqfd->gsi; > > > + level_irqfd = eventfd_ctx_get(irqfd->eventfd); > > > + source = _irq_source_get(irqfd->source); > > > + _irqfd_put_unlock(irqfd); > > > + if (!source) { > > > + ret = -EINVAL; > > > + goto fail; > > > + } > > > + } else { > > > + ret = -EINVAL; > > > + goto fail; > > > + } > > > + > > > + INIT_LIST_HEAD(&eoifd->list); > > > + eoifd->kvm = kvm; > > > + eoifd->eventfd = eventfd; > > > + eoifd->source = source; > > > + eoifd->level_irqfd = level_irqfd; > > > + eoifd->notifier.gsi = gsi; > > > + eoifd->notifier.irq_acked = eoifd_event; > > > > OK so this means eoifd keeps a reference to the irqfd. > > And since this is the case, can't we drop the reference counting > > around source ids now? Everything is referenced through irqfd. > > Holding a reference and using it as a reference count are not the same > thing. What if another module holds a reference to this eventfd? How > do we do anything on release? We don't as there is no release, and using kref on source id does not help: it just never gets invoked. -- MST