Runit assertions from other thread

Hi All,
I am using a sip framework (sipr) to test my sip server. sipr provides a
facility to write controller, which run entirely in its own thread. It
also provides a way to indicate end of sip controller, so that the test
thread can proceed ahead do verification.

So its all post facto verification.

However I need to do some assertion when my execution control is in sip
controller. e.g. When a successful call is established I want to assert
that my cli tool shows me one call in progress.

I want to know that how can I write this assert in my controller thread
which can let the results know to the main test thread which started the
controller thread.

Any pointers will be of great help.
Thanks and Regards,
Manish