Re: [Qemu-devel] [PATCH 2/5] qemu_coroutine_self should not be marked coroutine_fn as it cannot yield

[Charlie Shepherd]

On 07/08/2013 23:13, Gabriel Kerneis wrote:
> On Wed, Aug 07, 2013 at 09:18:05PM +0200, Stefan Hajnoczi wrote:
> > I guess the practical problem is that CPC will get
> > upset that it's being called by the coroutine implementation from
> > non-coroutine contexts.
> But is it really the case? If Charlie added an annotation, it probably means
> that in practice it was only called from coroutine context anyway.

It was also called from coroutine implementation in functions that 
weren't annotated coroutine_fn (qemu_coroutine_switch() and friends).

> The only downside from CPC's point of view is that there is a cost to making a
> coroutine_fn, and it's a pity to pay it when it's useless (ie. when the function
> never yields anyway).

Yes although in this case it won't be too high as the function will 
simply be

Coroutine *internal_qemu_coroutine_self(void);

coroutine_fn Coroutine *qemu_coroutine_self(void)
{
    return internal_qemu_coroutine_self();
}

and the original qemu_coroutine_self couldn't be inlined, so I don't 
think it is too prohibitive. Besides, I doubt qemu_coroutine_self() is 
called in many fast-paths.


Charlie