From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ian Campbell <ian.campbell@citrix.com>
Subject: Re: [PATCHv2 2/5] evtchn: simplify port_is_valid()
Date: Mon, 15 Jun 2015 17:09:09 +0100
Message-ID: <1434384549.13744.29.camel@citrix.com>
References: <1434383299-21833-1-git-send-email-david.vrabel@citrix.com>
	<1434383299-21833-3-git-send-email-david.vrabel@citrix.com>
	<1434383866.13744.28.camel@citrix.com> <557EF644.6020108@citrix.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
Received: from mail6.bemta5.messagelabs.com ([195.245.231.135])
	by lists.xen.org with esmtp (Exim 4.72)
	(envelope-from <prvs=601a95058=Ian.Campbell@citrix.com>)
	id 1Z4Xt2-0004TI-LZ
	for xen-devel@lists.xenproject.org; Mon, 15 Jun 2015 17:09:28 +0000
In-Reply-To: <557EF644.6020108@citrix.com>
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: David Vrabel <david.vrabel@citrix.com>
Cc: xen-devel@lists.xenproject.org, Keir Fraser <keir@xen.org>, Tim Deegan <tim@xen.org>, Jan Beulich <jbeulich@suse.com>
List-Id: xen-devel@lists.xenproject.org

On Mon, 2015-06-15 at 16:59 +0100, David Vrabel wrote:
> On 15/06/15 16:57, Ian Campbell wrote:
> > On Mon, 2015-06-15 at 16:48 +0100, David Vrabel wrote:
> >> By keeping a count of the number of currently valid event channels,
> >> port_is_valid() can be simplified.
> >>
> >> d->valid_evtchns can also be tested without holding d->event_lock which
> >> will be useful later on.
> >>
> >> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> >> ---
> >> v2:
> >> - Used unsigned int for d->valid_evtchns.
> >> ---
> >>  xen/common/event_channel.c |    3 +++
> >>  xen/include/xen/event.h    |    4 +---
> >>  xen/include/xen/sched.h    |    5 +++--
> >>  3 files changed, 7 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c
> >> index 947880f..fd48646 100644
> >> --- a/xen/common/event_channel.c
> >> +++ b/xen/common/event_channel.c
> >> @@ -189,6 +189,8 @@ static int get_free_port(struct domain *d)
> >>          return -ENOMEM;
> >>      bucket_from_port(d, port) = chn;
> >>  
> >> +    write_atomic(&d->valid_evtchns, d->valid_evtchns + EVTCHNS_PER_BUCKET);
> > 
> > Shouldn't this be atomic_add? Otherwise the result of what you have here
> > is actually a non-atomic read/add/write.
> 
> This field is only updated while holding d->event_lock.  Only reads are
> unlocked.

Oh good, thanks!

Ian.