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

[Anthony Liguori <aliguori@linux.vnet.ibm.com>]

On 03/26/2010 10:23 AM, Paul Brook wrote:
>> 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.
>    

I agree.  There's a lot of context missing from a proposal like this.

Regards,

Anthony Liguori

> Paul
>
>
>