Re: [Qemu-devel] [RFC] New thread for the VM migration

[Avi Kivity]

On 07/14/2011 03:30 PM, Anthony Liguori wrote:
> > Does this mean that the following code is sometimes executed without
> > qemu_mutex? I don't think any of it is thread safe.
>
>
> That was my reaction too.
>
> I think the most rational thing to do is have a separate thread and a 
> pair of producer/consumer queues.
>
> The I/O thread can push virtual addresses and sizes to the queue for 
> the migration thread to compress/write() to the fd.  The migration 
> thread can then push sent regions onto a separate queue for the I/O 
> thread to mark as dirty.

Even virtual addresses are not safe enough, because of hotunplug.  
Without some kind of locking, you have to copy the data.

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