Conference Papers: Type Safe Nondeterminism - A Formal Semantics of Java Threads

We present a generic framework to transform a single-threaded operational semantics into a semantics with interleaved execution of threads. Threads can be dynamically created and use locks for synchronisation. They can suspend themselves, be notified by other threads again, and interact via shared memory. We formalised this in the proof assistant Isabelle/HOL along with theorems to carry type safety proofs for the instantiating semantics (progress and preservation in the style of Wright and Felleisen) over to the multithreaded case, thereby investigating the role of deadlocks and giving an explicit formalisation for them. We apply this framework to the Java thread model using an extension of the Jinja source code semantics to have type safety for multithreaded Java machine-checked. The Java Memory Model is not included.