Re: [Qemu-devel] [PATCH 3/5] coroutines: abort if we try to enter a still-sleeping coroutine

[Jeff Cody]

On Tue, Nov 21, 2017 at 12:13:46AM +0100, Paolo Bonzini wrote:
> On 21/11/2017 00:08, Jeff Cody wrote:
> > @@ -34,6 +36,7 @@ void coroutine_fn co_aio_sleep_ns(AioContext *ctx, 
> > QEMUClockType type,
> >      CoSleepCB sleep_cb = {
> >          .co = qemu_coroutine_self(),
> >      };
> > +    if (sleep_cb.co->sleeping == 1 || sleep_cb.co->scheduled == 1) {
> > +       fprintf(stderr, "Cannot sleep a co-routine that is already sleeping 
> > "
> > +                       " or scheduled\n");
> > +       abort();
> > +    }
> > +    sleep_cb.co->sleeping = 1;
> >      sleep_cb.ts = aio_timer_new(ctx, type, SCALE_NS, co_sleep_cb, 
> > &sleep_cb);
> >      timer_mod(sleep_cb.ts, qemu_clock_get_ns(type) + ns);
> >      qemu_coroutine_yield();
> 
> I understand that this was just an example and not the actual patch, but
> I'll still point out that this loses the benefit (better error message)
> of keeping the flags separate.
> 
> What do you think about making "scheduled" a const char * and assigning
> __func__ to it (i.e. either "aio_co_schedule" or "co_aio_sleep_ns")?
> 

Ohhh, nice.  I'll spin a v2 with that, and merge patches 3 and 5 together.
And then maybe for 2.12 we can look at making it a fsm, like Stefan
suggested (or somehow make coroutine entry thread safe and idempotent).

Jeff