Re: [PATCH v3 06/33] util/async: aio_co_schedule(): support reschedule in same ctx

[Vladimir Sementsov-Ogievskiy]

12.05.2021 09:56, Paolo Bonzini wrote:
> On 16/04/21 10:08, Vladimir Sementsov-Ogievskiy wrote:
> > With the following patch we want to call wake coroutine from thread.
> > And it doesn't work with aio_co_wake:
> > Assume we have no iothreads.
> > Assume we have a coroutine A, which waits in the yield point for
> > external aio_co_wake(), and no progress can be done until it happen.
> > Main thread is in blocking aio_poll() (for example, in blk_read()).
> >
> > Now, in a separate thread we do aio_co_wake(). It calls  aio_co_enter(),
> > which goes through last "else" branch and do aio_context_acquire(ctx).
>
> I don't understand.  Why doesn't aio_co_enter go through the ctx != 
> qemu_get_current_aio_context() branch and just do aio_co_schedule?  That was at 
> least the idea behind aio_co_wake and aio_co_enter.

Because ctx is exactly qemu_get_current_aio_context(), as we are not in 
iothread but in nbd connection thread. So, qemu_get_current_aio_context() 
returns qemu_aio_context.


--
Best regards,
Vladimir