From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH 4/4] Convert irq notifiers lists to RCU locking.
Date: Mon, 13 Jul 2009 16:40:59 +0300
Message-ID: <20090713134058.GG10402@redhat.com>
References: <1247400233-24243-1-git-send-email-gleb@redhat.com> <1247400233-24243-5-git-send-email-gleb@redhat.com> <20090713130256.GC10402@redhat.com> <20090713131128.GI28046@redhat.com> <4A5B35FD.9090208@gmail.com> <20090713133234.GN28046@redhat.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: Gregory Haskins <gregory.haskins@gmail.com>, avi@redhat.com,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	paulmck@linux.vnet.ibm.com
To: Gleb Natapov <gleb@redhat.com>
Return-path: <kvm-owner@vger.kernel.org>
Received: from mx2.redhat.com ([66.187.237.31]:49602 "EHLO mx2.redhat.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1755764AbZGMNlt (ORCPT <rfc822;kvm@vger.kernel.org>);
	Mon, 13 Jul 2009 09:41:49 -0400
Content-Disposition: inline
In-Reply-To: <20090713133234.GN28046@redhat.com>
Sender: kvm-owner@vger.kernel.org
List-ID: <kvm.vger.kernel.org>

On Mon, Jul 13, 2009 at 04:32:34PM +0300, Gleb Natapov wrote:
> Yeah I understand that other RCU read section may introduce delays too.
> The question is how big the delay may be.

I recall seeing the number "at least 3 jiffies" somewhere, but that
might have changed since.

> I don't think multiple
> milliseconds delay in device de-assignment is a big issue though.

Right. My point was that since the sync is done under kvm lock, the
guest can easily get blocked trying to get kvm lock meanwhile.