On 07/14/2011 07:32 AM, Avi Kivity wrote:
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.
We don't know yet how we're going to implement hot unplug so let's not
worry about this for now.
I think a reference count based approach is really the only sane thing
to do and if we did that, it wouldn't be a problem since the reference
would be owned by the I/O thread and would live until the migration
thread is done with the VA.
Regards,
Anthony Liguori
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