Deadlock analysis of multi-threaded programs with reentrant locks is complex because these programs may have infinitely many states. We define a simple calculus featuring recursion, threads and synchroniza-tions that guarantee exclusive access to objects. We detect deadlocks by associating an abstract model to programs-the extended lam model-and we define an algorithm for verifying that a problematic object dependency (e.g. a circularity) between threads will not be manifested. The analysis is lightweight because the deadlock detection problem is fully reduced to the corresponding one in lams (without using other models). The technique is intended to be an effective tool for the deadlock analysis of programming languages by defining ad-hoc extraction processes.