Re: [PATCH] aio-posix: split poll check from ready handler

[Stefan Hajnoczi]

On Wed, Dec 01, 2021 at 12:55:08PM +0100, Stefano Garzarella wrote:
> On Tue, Nov 30, 2021 at 11:20:57AM +0000, Stefan Hajnoczi wrote:
> > @@ -657,10 +704,7 @@ bool aio_poll(AioContext *ctx, bool blocking)
> >     }
> > 
> >     progress |= aio_bh_poll(ctx);
> > -
> > -    if (ret > 0) {
> > -        progress |= aio_dispatch_ready_handlers(ctx, &ready_list);
> > -    }
> > +    progress |= aio_dispatch_ready_handlers(ctx, &ready_list);
> 
> I honestly don't know this code well, so this change isn't clear to me.
> 
> IIUC this is necessary because we now use REVENTS_POLL_READY, so even if
> `wait` is interrupted, we want to run the handlers ready so far.
> Or maybe is it an unrelated optimization?

Previously we didn't need to run aio_dispatch_ready_handlers() in
polling mode (ret would be 0). Now we do, so the conditional needs to be
removed.

There is no change for the ctx->fdmon_ops->wait() -EINTR case. fdmon
won't add handlers to ready_list when returning -EINTR and previously
polling would run handlers immediately. In order to preserve that
behavior we now need to call aio_dispatch_ready_handlers()
unconditionally because polling may have added handlers.

Stefan

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