KERNEL DESIGN ISSUES - Hard Real-Time Computing Systems: Predictable Scheduling Algorithms and Applications - page 359

Semaphore Control Block

counter

semaphore queue

pointer to the next SCB

Figure 10.10 Semaphore Control Block.

Each SCB is an element of the vsem[MAXSEM] array, whose size is equal to the maxi-
mum number of semaphores handled by the kernel. According to this approach, tasks,
semaphores, and queues can be accessed by an integer number that represents the
index of the corresponding control block. For the sake of clarity, however, tasks,
semaphores and queues are defined as three different types.

typedef int queue; /* head index */

typedef int sem; /* semaphore index */

typedef int proc; /* process index */

typedef int cab; /* cab buffer index */

typedef char* pointer; /* memory pointer */