The top level BMI user interface is thread safe. This means that it is legal for more than one thread to make concurrent BMI calls, as long as those calls do not manipulate the same data structures or operations. For example, one thread may handle BMI messages to carry out I/O, while another thread handles BMI messages to exchange requests and acknowledgements.
The BMI methods do not need to be thread safe. The method control layer will serialize any calls to a single method so that it is protected. This should ease the process of implementing new methods.