Synchronizing Multiple Tasks

Synchronizing the execution of multiple tasks by broadcasting to a semaphore is a commonly used technique. It may be important to have multiple tasks start executing at the same time. Obviously, on a single processor, only one task will actually execute at one time. However, the start of their execution will be synchronized to the same time. This is called a multiple task rendez-vous. However, some of the tasks synchronized might not be waiting for the semaphore when the broadcast is performed. It is fairly easy to resolve this problem by combining semaphores and event flags, as shown in the figure below For this to work properly, the task on the left needs to have a lower priority than the tasks waiting on the semaphore.