Re: [Qemu-devel] [PATCH v2 3/3] AioContext: fix broken ctx->dispatching optimization

[Paolo Bonzini <pbonzini@redhat.com>]

On 16/07/2015 11:56, Paolo Bonzini wrote:
> @@ -286,13 +283,15 @@ bool aio_poll(AioContext *ctx, bool blocking)
>      npfd = 0;
>      ctx->walking_handlers--;
>  
> +    if (blocking) {
> +        atomic_sub(&ctx->notify_me, 2);
> +    }
> +

I kept this place for subtracting notify_me because it is the same place
where aio_set_dispatching was called.  However, it can be anticipated to

     /* if we have any readable fds, dispatch event */
     if (ret > 0) {
         for (i = 0; i < npfd; i++) {

i.e. right after poll.  As poll has exited, it can't be blocking the
thread anymore.  Stefan, please let me send v3 on Monday.

Paolo

> 
>      /* Run dispatch even if there were no readable fds to run timers */
> -    aio_set_dispatching(ctx, true);
>      if (aio_dispatch(ctx)) {
>          progress = true;
>      }
>