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Date: Mon, 12 Aug 2013 03:30:28 -0400 (EDT)
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [RFC] Convert AioContext to Gsource sub classes
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To: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Anthony Liguori <aliguori@us.ibm.com>, Ping Fan Liu <pingfank@linux.vnet.ibm.com>, Stefan Hajnoczi <stefanha@gmail.com>, Michael Roth <mdroth@linux.vnet.ibm.com>, qemu-devel <qemu-devel@nongnu.org>


> 1) rename AioContext to AioSource.
>   This is my major purpose, which declare it is not a "context" concept,
> and GMainContext is the entity represent the thread's activity.

Note that the nested event loops in QEMU are _very_ different from
glib nested event loops.  In QEMU, nested event loops only run block
layer events.  In glib, they run all events.  That's why you need
AioContext.

> 2) Break AioSource into FdSource and BhSource.
>   This make custom code less and simpler, one Gsource for one kind of
> job. It is not necessary but IMHO it will make things clear when add
> more things into main loop: add a new Gsource sub class, avoid to
> always have relationship with AioContext.

But this is only complicating things work since users rely on both file-
descriptor APIs and bottom half APIs.

> >>    More reasons:
> >>    When I thinking how to bind library code to a thread context, it may
> >> need to add Context's concept into API of block.c. If I use AioContext,
> >> there will need a wrapper API to run the event loop. But If I got
> >> glib's GmainContext, things become simple.

You already have it because AioContext is a GSource.  You do not need
to expose the AioContext, except as a GSource.

Paolo