I don't understand. I am confused about it.

I don't understand. I am confused about the general Linux technology-Linux programming and kernel information. here is the details.

CODE: # include # Include # Include # Include Pthread_cond_t taxiCond = PTHREAD_COND_INITIALIZER; Pthread_mutex_t taxiMutex = PTHREAD_MUTEX_INITIALIZER; Void * traveler_arrive (void * name) { Int ret; Printf ("Traveler % s needs a taxi now1 \ n", name ); Ret = pthread_mutex_lock (& taxiMutex ); If (ret = 0) printf ("cond is locked \ n "); Pthread_cond_wait (& taxiCond, & taxiMutex ); Printf ("test \ n "); Pthread_mutex_unlock (& taxiMutex ); Printf ("% s got a taxi \ n", name ); Printf ("traver thread sucess and exit \ n "); Pthread_exit (void *) 0 ); } Void * taxi_arrive (void * name) { Int ret; Printf ("taxi % s arrive \ n", name ); Pthread_mutex_unlock (& taxiMutex ); Ret = pthread_cond_signal (& taxiCond ); If (ret = 0) printf ("cond is lived \ n "); Pthread_mutex_unlock (& taxiMutex ); Printf ("taxi thread sucess and exit \ n "); Pthread_exit (void *) 0 ); } Void main () { Pthread_t thread; Pthread_attr_t threadAttr; Pthread_attr_init (& threadAttr ); Pthread_create (& thread, & threadAttr, taxi_arrive, (void *) ("Jack ")); Sleep (10 ); Pthread_create (& thread, & threadAttr, traveler_arrive, (void *) ("Susan ")); Sleep (10 ); Pthread_create (& thread, & threadAttr, taxi_arrive, (void *) ("Mike ")); Sleep (10 ); Return; }