Abstract: A deadlock free synchronization synthesizer for must-happen-before relations in at least two parallel programs or at least two threads each having multiple code segments has an input device to specify a synchronization point to involving code segments for each parallel program or thread and must-happen-before relations to the synchronization point, an analyzing module connected to the input device to detect existence of a deadlock in the parallel programs by using the must-happen-before relations, and a synthesizing module connected to the analyzing module to synthesize a practice code corresponding to the parallel programs if the deadlock existence detection is negative.