From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel De Graaf Subject: Re: [PATCH v3] libvchan: interdomain communications library Date: Thu, 01 Sep 2011 13:46:13 -0400 Message-ID: <4E5FC4E5.4070704@tycho.nsa.gov> References: <20055.42803.979775.531468@mariner.uk.xensource.com> <1314643714-28350-1-git-send-email-dgdegra@tycho.nsa.gov> <1314700361.10283.135.camel@zakaz.uk.xensource.com> <4E5E88CF.7090408@tycho.nsa.gov> <1314894519.28989.143.camel@zakaz.uk.xensource.com> <4E5FB72B.7010200@tycho.nsa.gov> <20063.47441.576537.375177@mariner.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20063.47441.576537.375177@mariner.uk.xensource.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Ian Jackson Cc: Ian Campbell , "xen-devel@lists.xensource.com" , Stefano Stabellini , "konrad.wilk@oracle.com" List-Id: xen-devel@lists.xenproject.org On 09/01/2011 12:56 PM, Ian Jackson wrote: > Daniel De Graaf writes ("Re: [PATCH v3] libvchan: interdomain communications library"): >> Making this change has exposed an interesting ordering dependency in the >> notify API under Linux: the file descriptor for gntdev or gntalloc must be >> less than the file descriptor for evtchn in order for the event channel to >> still be active when the unmap occurs on a crash. The init functions of >> libvchan do open the files in the proper order for this to happen. > > Wow, that's pretty crazy. Surely the gnt* fd should have an internal > reference to the evtchn fd ? > > Ian. > The gnt* drivers will need to be changed to both find and take such a reference; currently, they only refer to the port. This will probably add a dependency from the gnt* module on evtchn; I'll look at what is actually required to hold the event channel open when I make the patch. -- Daniel De Graaf National Security Agency