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Date: Thu, 28 Mar 2013 15:47:48 +0100
From: Stefan Hajnoczi <stefanha@gmail.com>
Message-ID: <20130328144748.GJ22865@stefanha-thinkpad.redhat.com>
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Subject: Re: [Qemu-devel] [RFC PATCH v2 3/4] net: port hub onto glib
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To: Liu Ping Fan <qemulist@gmail.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>, Anthony Liguori <aliguori@us.ibm.com>, qemu-devel@nongnu.org, mdroth <mdroth@linux.vnet.ibm.com>

On Thu, Mar 28, 2013 at 03:55:54PM +0800, Liu Ping Fan wrote:
> From: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
> 
> Attach each hubport with a GSource. Currently the GSource is attached
> to default main context, and the hub still run on iothread, but in
> future, after making the whole layer thread-safe, we will admit ports
> to run on different thread.
> 
> Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
> ---
>  hw/qdev-properties-system.c |    1 +
>  include/net/queue.h         |   14 ++++++++++++++
>  net/hub.c                   |   34 ++++++++++++++++++++++++++++++++--
>  net/net.c                   |    1 +
>  net/queue.c                 |    4 ++--
>  5 files changed, 50 insertions(+), 4 deletions(-)

There are two possibilities when a hub is used:

1. All net clients on the hub run in the same event loop.

We don't need any code changes to make this work.

2. Net clients run in different event loops.

I don't think this case matters, let's forbid it.  It's not worth adding
more complexity to the net subsystem in order to support it.

Can you think of a use case that is well-served by net clients in
multiple event loops?

Stefan