From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758067AbZEZUGh (ORCPT ); Tue, 26 May 2009 16:06:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757011AbZEZUG3 (ORCPT ); Tue, 26 May 2009 16:06:29 -0400 Received: from x35.xmailserver.org ([64.71.152.41]:59130 "EHLO x35.xmailserver.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756686AbZEZUG2 (ORCPT ); Tue, 26 May 2009 16:06:28 -0400 X-AuthUser: davidel@xmailserver.org Date: Tue, 26 May 2009 13:00:26 -0700 (PDT) From: Davide Libenzi X-X-Sender: davide@makko.or.mcafeemobile.com To: "Michael S. Tsirkin" cc: Gregory Haskins , kvm@vger.kernel.org, Linux Kernel Mailing List , avi@redhat.com, mtosatti@redhat.com Subject: Re: [KVM PATCH v10] kvm: add support for irqfd In-Reply-To: <20090526164201.GD9842@redhat.com> Message-ID: References: <20090520142234.22285.72274.stgit@dev.haskins.net> <20090526164201.GD9842@redhat.com> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) X-GPG-FINGRPRINT: CFAE 5BEE FD36 F65E E640 56FE 0974 BF23 270F 474E X-GPG-PUBLIC_KEY: http://www.xmailserver.org/davidel.asc MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 26 May 2009, Michael S. Tsirkin wrote: > On Wed, May 20, 2009 at 10:30:49AM -0400, Gregory Haskins wrote: > > +static int > > +irqfd_wakeup(wait_queue_t *wait, unsigned mode, int sync, void *key) > > +{ > > + struct _irqfd *irqfd = container_of(wait, struct _irqfd, wait); > > + > > + /* > > + * The wake_up is called with interrupts disabled. Therefore we need > > + * to defer the IRQ injection until later since we need to acquire the > > + * kvm->lock to do so. > > + */ > > + schedule_work(&irqfd->work); > > + > > + return 0; > > +} > > This schedule_work is there just to work around the spinlock > in eventfd_signal, which we don't really need. Isn't this right? > And this is on each interrupt. Seems like a pity. > How about a flag in eventfd that would > convert it from waking up someone to a plain function call? > > Davide, could we add something like I'm sorry, but it's not very pretty. Please find another way around. > diff --git a/fs/eventfd.c b/fs/eventfd.c > index 2a701d5..8bfa308 100644 > --- a/fs/eventfd.c > +++ b/fs/eventfd.c > @@ -29,6 +29,7 @@ struct eventfd_ctx { > */ > __u64 count; > unsigned int flags; > + int nolock; > }; > > /* > @@ -46,6 +47,12 @@ int eventfd_signal(struct file *file, int n) > > if (n < 0) > return -EINVAL; > + if (ctx->nolock) { > + /* Whoever set nolock > + better set wqh.func as well. */ > + ctx->wqh.func(&ctx->wqh, 0, 0, NULL); > + return 0; > + } > spin_lock_irqsave(&ctx->wqh.lock, flags); > if (ULLONG_MAX - ctx->count < n) > n = (int) (ULLONG_MAX - ctx->count); - Davide