Re: [Qemu-devel] [patch 1/2] Pass QEMUIOWorker to qemu_notify_event

[Paul Brook]

> On Thu, Mar 25, 2010 at 09:06:00PM +0000, Paul Brook wrote:
> > >  /* Force QEMU to process pending events */
> > > -void qemu_notify_event(void);
> > > +void qemu_notify_event(QEMUIOWorker *worker);
> > >
> > >  static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
> > >  {
> > > +    qemu_notify_event(main_io_worker);
> > >  }
> >
> > This feels completely wrong.
> >
> > Devices shouldn't know or care about implementation details like this.
> > How is a device supposed to know which worker it should be waking up?
> 
> Its not. It could use qemu_notify_event(DeviceInfo->worker), and have no
> knowledge of the internals.

In that case I think you're abusing this API.

I'm very wary of introducing random bits of code that allegedly allow future 
use of threads.  Exploiting thread level parallelism is a hard problem that 
needs proper design.  A such I object to this patch, and think we first need 
to decide what form of concurrency model we want to use in QEMU.

Paul