Re: [Qemu-devel] [PATCH v2] net-hub: Drop can_receive

[Fam Zheng]

On Tue, 07/21 09:36, Stefan Hajnoczi wrote:
> On Tue, Jul 21, 2015 at 09:27:56AM +0800, Fam Zheng wrote:
> > On Mon, 07/20 18:07, Stefan Hajnoczi wrote:
> > > On Tue, Jul 07, 2015 at 05:41:56PM +0800, Fam Zheng wrote:
> > > > On Tue, 07/07 09:37, Stefan Hajnoczi wrote:
> > > > > On Tue, Jul 07, 2015 at 02:30:30PM +0800, Fam Zheng wrote:
> > > > > > This moves the semantics from net_hub_port_can_receive to receive
> > > > > > functions, by returning 0 if all receiving ports return 0. Also,
> > > > > > remember to flush the source port's queue in that case.
> > > > > > 
> > > > > > Signed-off-by: Fam Zheng <address@hidden>
> > > > > > ---
> > > > > >  net/hub.c | 54 
> > > > > > +++++++++++++++++++++++++++++-------------------------
> > > > > >  1 file changed, 29 insertions(+), 25 deletions(-)
> > > > > 
> > > > > This patch revision doesn't take into account the special case code in
> > > > > qemu_flush_or_purge_queued_packets(), which I mentioned in my reply to
> > > > > the previous revision of this patch.
> > > > > 
> > > > > The queue is now flushed twice because you've introduced
> > > > > net_hub_port_send_cb() but qemu_flush_or_purge_queued_packets() 
> > > > > already
> > > > > calls net_hub_flush().
> > > > > 
> > > > > If you want to get rid of net_hub_flush(), that's great.  But please
> > > > > remove the duplicate code.
> > > > 
> > > > Right, I missed that. I'll remove the duplicate and send again.
> > > 
> > > Ping?
> > 
> > I thought the net_hub_flush in qemu_flush_or_purge_queued_packets already 
> > makes
> > sure net-hub is working, so it's just about cleaning up. That's why I 
> > deferred
> > this to 2.5.  Am I wrong?
> 
> My concern was that your NIC patches remove .can_receive() functions but
> net/hub.c still relies on them via qemu_can_send_packet().
> 
> After thinking about it more, the code should still work the same even
> though net_hub_can_receive() is now mostly useless and should be removed
> in QEMU 2.5.

Yes. Completely removing .can_receive from the code base for 2.5 is trivial if
the proposed fixes are correct, but it doesn't matter much now.

> 
> We can leave this patch for now.

OK, so net-hub is cleared, please proceed with merging the bulk .can_receive
series, or if there are other issues, revert the qemu_set_fd_handler .can_send
patches and I'll redo it in 2.5.

Fam