From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [PATCHv3 2/6] evtchn: defer freeing struct evtchn's until evtchn_destroy_final() Date: Fri, 19 Jun 2015 10:52:21 +0100 Message-ID: <5583E655.2070807@citrix.com> References: <1434542583-28073-1-git-send-email-david.vrabel@citrix.com> <1434542583-28073-3-git-send-email-david.vrabel@citrix.com> <5582BB4C02000078000868FB@mail.emea.novell.com> <5582A02A.9050803@citrix.com> <5583FD0F0200007800086EF1@mail.emea.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta3.messagelabs.com ([195.245.230.39]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1Z5syJ-00069I-6J for xen-devel@lists.xenproject.org; Fri, 19 Jun 2015 09:52:27 +0000 In-Reply-To: <5583FD0F0200007800086EF1@mail.emea.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jan Beulich , David Vrabel Cc: xen-devel@lists.xenproject.org, Keir Fraser , Ian Campbell , Tim Deegan List-Id: xen-devel@lists.xenproject.org On 19/06/15 10:29, Jan Beulich wrote: >>>> On 18.06.15 at 12:40, wrote: >> On 18/06/15 11:36, Jan Beulich wrote: >>>>>> On 17.06.15 at 14:02, wrote: >>>> --- a/xen/common/event_channel.c >>>> +++ b/xen/common/event_channel.c >>>> @@ -1175,22 +1175,6 @@ int alloc_unbound_xen_event_channel( >>>> >>>> void free_xen_event_channel(struct domain *d, int port) >>>> { >>>> - struct evtchn *chn; >>>> - >>>> - spin_lock(&d->event_lock); >>>> - >>>> - if ( unlikely(d->is_dying) ) >>>> - { >>>> - spin_unlock(&d->event_lock); >>>> - return; >>>> - } >>>> - >>>> - BUG_ON(!port_is_valid(d, port)); >> >> I can keep this one. >> >>>> - chn = evtchn_from_port(d, port); >>>> - BUG_ON(!consumer_is_xen(chn)); >>> >>> At least in debug builds I think these would better be retained. >> >> But this one has to go because it will always trip when >> free_xen_event_channel() is called after evtchn_destroy() (which will >> have cleared xen_consumer). > > Then why not > > BUG_ON(!consumer_is_xen(chn) && !d->is_dying); > > or keep the d->is_dying check in place? I can see why accelerating > notify_via_xen_event_channel() is useful, but > free_xen_event_channel()? This BUG_ON() is a pretty weak check and I don't really see the point of it. I'm not respinning v4 just for this. David