From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57718) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bwSmR-0008Kk-Kq for qemu-devel@nongnu.org; Tue, 18 Oct 2016 07:42:05 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bwSmQ-0007w5-8N for qemu-devel@nongnu.org; Tue, 18 Oct 2016 07:42:03 -0400 Received: from mail-lf0-x232.google.com ([2a00:1450:4010:c07::232]:33479) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1bwSmP-0007vG-Qs for qemu-devel@nongnu.org; Tue, 18 Oct 2016 07:42:02 -0400 Received: by mail-lf0-x232.google.com with SMTP id x79so351454359lff.0 for ; Tue, 18 Oct 2016 04:42:01 -0700 (PDT) MIME-Version: 1.0 References: <20161012191502.GC16187@work-vm> <20161018100409.GH4349@redhat.com> <20161018113202.GE2190@work-vm> In-Reply-To: <20161018113202.GE2190@work-vm> From: =?UTF-8?B?TWFyYy1BbmRyw6kgTHVyZWF1?= Date: Tue, 18 Oct 2016 11:41:48 +0000 Message-ID: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] chardev's and fd's in monitors List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert" , "Daniel P. Berrange" Cc: qemu-devel@nongnu.org, armbru@redhat.com Hi On Tue, Oct 18, 2016 at 2:32 PM Dr. David Alan Gilbert wrote: > * 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. > > > > > > If we could get away with just a FILE* then we could use fopencookie, > > > but that's GNU only. > > > > > > Is there any sane way of shepherding all chardev's into having an > > > fd? > > > > 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 > streams > to be FILE*'s. > glibc can have custom streams iirc: https://www.gnu.org/software/libc/manual/html_node/Custom-Streams.html#Cust= om-Streams I haven't looked in details if that would solve it. > > 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 w= e > 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 usefu= l. > > > 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=C3=A9 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 > from 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 > chardev > b) I'd eventually like multiple monitor threads. > > Dave > > > Regards, > > Daniel > > -- > > |: http://berrange.com -o- > http://www.flickr.com/photos/dberrange/ :| > > |: http://libvirt.org -o- > http://virt-manager.org :| > > |: http://entangle-photo.org -o- > http://search.cpan.org/~danberr/ :| > -- > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK > > -- Marc-Andr=C3=A9 Lureau