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Date: Thu, 14 Mar 2013 11:53:19 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [RFC PATCH 0/2] port network layer onto glib
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: mdroth <mdroth@linux.vnet.ibm.com>, "Michael S. Tsirkin" <mst@redhat.com>, Stefan Hajnoczi <stefanha@gmail.com>, qemu-devel@nongnu.org, Liu Ping Fan <qemulist@gmail.com>, Anthony Liguori <anthony@codemonkey.ws>

Il 14/03/2013 11:04, Peter Maydell ha scritto:
> On 13 March 2013 12:34, Anthony Liguori <anthony@codemonkey.ws> wrote:
>> AioContext is necessary for the block layer because the block layer
>> still has synchronous I/O.  I think we should aim to replace all sync
>> I/O in the long term with coroutine based I/O.
> 
> I think coroutines are dreadful and we should really not be moving
> towards greater use of them. They're just really really not portable
> and they don't fit with the C language, and they're a constant source
> of problems.(For instance I have a bug I need to look into where we
> seem to hang using the gthread coroutine backend but not sigaltstack.)

The gthread coroutine backend is really more for debugging than anything
else.  It works for qemu-io/img, but not for QEMU.  Good that you
actually found proof. :)

Paolo

> Use threads, or a genuinely asynchronous API, or a select/poll loop
> with callbacks, but not more coroutines please.
> 
> -- PMM
>