Re: [Qemu-devel] [RFC PATCH v2 1/4] net: port tap onto glib

[Stefan Hajnoczi <stefanha@gmail.com>]

On Wed, Apr 03, 2013 at 05:28:39PM +0800, liu ping fan wrote:
> On Thu, Mar 28, 2013 at 10:32 PM, Stefan Hajnoczi <stefanha@gmail.com> wrote:
> > On Thu, Mar 28, 2013 at 03:55:52PM +0800, Liu Ping Fan wrote:
> >> From: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
> >>
> >> Bind each NetClientState with a GSource(ie,NetClientSource). Currently,
> >> these GSource attached with default context, but in future, after
> >> resolving the race between handlers and the interface exposed by NetClientInfo
> >> and other re-entrant issue,  we can run NetClientState on different threads
> >>
> >> Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
> >> ---
> >>  include/net/net.h |   27 +++++++++++++++
> >>  net/net.c         |   96 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> >>  net/tap.c         |   57 +++++++++++++++++++++++++------
> >>  3 files changed, 169 insertions(+), 11 deletions(-)
> >
> > Please split this into two patches:
> >
> > 1. NetClientSource
> > 2. Convert tap to NetClientSource
> >
> > Once you do that it turns out that NetClientSource has nothing to do
> > with the net subsystem, it's a generic file descriptor GSource (weird
> > that glib doesn't already provide this abstraction).
> >
> > Each net client needs to reimplement .bind_ctx() anyway, so I don't see
> > much point in having NetClientSource.nsrc[].  We might as well let net
> > clients have that field themselves and destroy the GSource in their
> > destructor function.
> >
> The only way to detach the GSource from GMainContext is
> g_source_destroy, so if we want to re-bind nc from threadA to threadB,
>  we should destroy the old one and create a new. Is that meaningful?

I guess that can be done.

What I was really thinking when I suggested getting rid of nsrc[] is
that it's a little ugly to have the array with 2 GSources.  Different
net clients have different numbers of GSources - 0 for NICs, 1 for most
backends, 2 for ioeventfd for virtio-net data plane with separate rx/tx.

So my thought was to leave the number of GSources in the layer that uses
them - each specific net client.

Stefan