Set the query callback function and user data that will be called after
collectpads has received a query originating from one of the collected
pads. If the query being processed is a serialized one, this callback is
called with @pads STREAM_LOCK held, otherwise not. As this lock should be
held when calling a number of CollectPads functions, it should be acquired
if so (unusually) needed.
Set the query callback function and user data that will be called after collectpads has received a query originating from one of the collected pads. If the query being processed is a serialized one, this callback is called with @pads STREAM_LOCK held, otherwise not. As this lock should be held when calling a number of CollectPads functions, it should be acquired if so (unusually) needed.
MT safe.