The semantics are the same as for any threaded use of a callback queue.
 What that means exactly depends on the callback you're talking about, so,
for example, subscription callbacks on a single topic will not happen in
multiple threads at once unless it's enabled in SubscribeOptions.

Josh

On Fri, Nov 26, 2010 at 9:46 AM, Jack O'Quin <jack.oquin@gmail.com> wrote:

> Despite searching the nodelet code and documentation, I'm having
> trouble grasping the semantics of multi-threaded nodelets.
>
> When would I want to call the getMT* methods for callback queues and
> node handles? What advantages do they provide?
>
> What are their threading and locking requirements, versus the
> single-thread versions?
>
> Is there any plan for a Documentation review of the nodelets package?
> --
>  joq
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