1 #include <semaphore.h> 2 #include <limits.h> 3 #include "pthread_impl.h" 4 sem_post(sem_t * sem)5int sem_post(sem_t *sem) 6 { 7 int val, new, waiters, priv = sem->__val[2]; 8 do { 9 val = sem->__val[0]; 10 waiters = sem->__val[1]; 11 if ((val & SEM_VALUE_MAX) == SEM_VALUE_MAX) { 12 errno = EOVERFLOW; 13 return -1; 14 } 15 new = val + 1; 16 if (waiters <= 1) 17 new &= ~0x80000000; 18 } while (a_cas(sem->__val, val, new) != val); 19 if (val<0) __wake(sem->__val, waiters>1 ? 1 : -1, priv); 20 return 0; 21 } 22