--- /dev/null
+Semaphores pseudocode
+==============================
+
+ int sem_wait(sem_t * sem);
+ int sem_trywait(sem_t * sem);
+ int sem_post(sem_t * sem);
+ int sem_getvalue(sem_t * sem, int * sval);
+
+struct sem_t {
+
+ unsigned int count;
+ - current semaphore count, also used as a futex
+}
+
+sem_wait(sem_t *sem)
+{
+ for (;;) {
+
+ if (atomic_decrement_if_positive(sem->count))
+ break;
+
+ futex_wait(&sem->count, 0)
+ }
+}
+
+sem_post(sem_t *sem)
+{
+ n = atomic_increment(sem->count);
+ // Pass the new value of sem->count
+ futex_wake(&sem->count, n + 1);
+}
+
+sem_trywait(sem_t *sem)
+{
+ if (atomic_decrement_if_positive(sem->count)) {
+ return 0;
+ } else {
+ return EAGAIN;
+ }
+}
+
+sem_getvalue(sem_t *sem, int *sval)
+{
+ *sval = sem->count;
+ read_barrier();
+}