From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56100) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bwScs-0004as-OC for qemu-devel@nongnu.org; Tue, 18 Oct 2016 07:32:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bwScp-0004q1-0c for qemu-devel@nongnu.org; Tue, 18 Oct 2016 07:32:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37270) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1bwSco-0004ph-Rk for qemu-devel@nongnu.org; Tue, 18 Oct 2016 07:32:06 -0400 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 2F6EB4E4F3 for ; Tue, 18 Oct 2016 11:32:06 +0000 (UTC) Date: Tue, 18 Oct 2016 12:32:02 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20161018113202.GE2190@work-vm> References: <20161012191502.GC16187@work-vm> <20161018100409.GH4349@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: <20161018100409.GH4349@redhat.com> Subject: Re: [Qemu-devel] chardev's and fd's in monitors List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Daniel P. Berrange" Cc: qemu-devel@nongnu.org, armbru@redhat.com * Daniel P. Berrange (berrange@redhat.com) wrote: > On Wed, Oct 12, 2016 at 08:15:02PM +0100, Dr. David Alan Gilbert wrote: > > Hi, > > I had a look at a couple of readline like libraries; > > editline and linenoise. A difficulty with using them is that > > they both want fd's or FILE*'s; editline takes either but > > from a brief look I think it's expecting to extract the fd. > > That makes them tricky to integrate into qemu, where > > the chardev's hide a whole bunch of non-fd things; in particular > > tls, mux, ringbuffers etc. > >=20 > > If we could get away with just a FILE* then we could use fopencookie, > > but that's GNU only. > >=20 > > Is there any sane way of shepherding all chardev's into having an > > fd? >=20 > The entire chardev abstraction model exists precisely because we cannot > make all chardevs look like a single fd. Even those which are fd based > may have separate FDs for input and output. Note that editline takes separate in/out streams, but it does want those st= reams to be FILE*'s. > IMHO the only viable approach would be to enhance linenoise/editline to > not assume use of fd* or FILE * abstractions. I think if it came to that then we'd probably end up sticking with what we had for a very long time; I'd assume it would take a long time before any mods we made to the libraries would come around to be generally useful. > BTW, what is the actual thread issue you are facing ? Chardevs at least > ought to be usable from a separate thread, as long as each distinct > chardev object instance was only used from one thread at a time ? Marc-Andr=E9 pointed that out; I hadn't realised they were thread safe. But what are the rules? You say 'only used from one thread at a time' - what happens if we have a mux and the different streams to the mux come =66rom different threads? My actual thoughts for threads came from a few sides: a) Maybe I could have a shim thread that fed the editline fd from a chard= ev b) I'd eventually like multiple monitor threads. Dave > Regards, > Daniel > --=20 > |: http://berrange.com -o- http://www.flickr.com/photos/dberrange= / :| > |: http://libvirt.org -o- http://virt-manager.or= g :| > |: http://entangle-photo.org -o- http://search.cpan.org/~danberr= / :| -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK