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Date: Wed, 28 Apr 2010 08:25:59 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: [Qemu-devel] Re: [PATCH v6 18/18] virtio-serial-bus: wake up
 iothread upon guest read notification
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To: Amit Shah <amit.shah@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>, qemu list <qemu-devel@nongnu.org>, Juan Quintela <quintela@redhat.com>

On 04/28/2010 02:29 AM, Amit Shah wrote:
> On (Tue) Apr 27 2010 [12:41:27], Anthony Liguori wrote:
>    
>> On 04/27/2010 07:34 AM, Amit Shah wrote:
>>      
>>> From: Marcelo Tosatti<mtosatti@redhat.com>
>>>
>>> Wake up iothread when buffers are consumed.
>>>
>>> Signed-off-by: Marcelo Tosatti<mtosatti@redhat.com>
>>> Signed-off-by: Amit Shah<amit.shah@redhat.com>
>>>
>>>        
>> What's the race here?  This looks very odd to me.
>>      
> When the guest indicates it has added buffers to the vq, the iothread
> can then start consuming them. Without this notification, the iothread
> only polls for free buffers when it times out or gets woken up
> otherwise.
>    

When you say, polls for free buffers, what do you mean by that?

You mean, there's a can_read() somewhere that checks for free buffers?

I think switching to qemu_set_fd_handler() would be a better solution.

Regards,

Anthony Liguori

> Other virtio devices do it similarly as well.
>
> 		Amit
>