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Date: Thu, 29 Aug 2013 13:43:02 +0100
From: Charlie Shepherd <charlie@ctshepherd.com>
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Subject: Re: [Qemu-devel] [RFC v2 05/15] Make qcow2_open synchronous
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: kwolf@redhat.com, pbonzini@redhat.com, gabriel@kerneis.info, qemu-devel@nongnu.org

On 29/08/2013 13:33, Stefan Hajnoczi wrote:
> On Fri, Aug 09, 2013 at 07:43:55PM +0200, Charlie Shepherd wrote:
>> The previous patch convert all .bdrv_open functions to run from a coroutine context. However
>> qcow2's open method is also called from qcow2_invalidate_cache. bdrv_invalidate_cache is mainly
>> called by migration.c, which doesn't run in coroutine context, so rather than propagating
>> coroutine_fn annotations up the call chain, turn qcow2_open into a synchronous wrapper.
> I think it would be cleaner to make .bdrv_open a coroutine function and
> push the synchronous wrapper out to the callers.  That way we can either
> keep synchronous wrappers where necessary, or we can eventually convert
> that synchronous code to coroutine code.
>
> If you hide the synchronous wrapper inside qcow2 it blocks coroutine
> callers who could otherwise use the event loop.

So you want this approach for all synchronous wrappers?


Charlie