Re: [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock

[Avi Kivity]

On 09/19/2012 12:14 PM, Paolo Bonzini wrote:

> I don't know if the front-end (device) lock should come before or after
> the back-end (e.g. netdev) lock in the hierarchy, but that's another story.

I would say device -> backend.  It's natural if the backend is the timer
subsystem, so extend it from there to the block and network layers.  Of
course callbacks want it to be the other way round.

We could solve the callback problem in the same way we're using for mmio
callbacks.  When providing the callback, give the subsystem ->ref() and
->unref() methods.  As long as a callback is pending, the subsystem
holds a reference.  Once the callback has been invoked or cancelled, the
reference can be released.

-- 
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