“to solve mutual exclusion problems among concurrent threads”
Birrell’s mechanisms: Pthreads:
-mutex
pthread_mutex_t aMutex; // mutex type
-Lock(mutex)
// explicit lock
int pthread_mutex_lock(pthread_mutex_t
*mutex);
// explicit unlock
int pthread_mutex_unlock(pthread_mutex_t
*mutex);
Other mutex operation
int pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *attr); // mutex attributes == specifies mutex behavior when // a mutex is shared among processes
int pthread_mutex_trylock(pthread_mutex_t *mutex);
-shared data should always be accessed through a single mutex
-mutex scope must be visible to all
-globally order lock
for all threads, lock mutexes in order
-always unlock a mutex
always unlock the correct mutex
Pthread Condition Variables
-condition
pthread_cond_t aCond; // type of cond variable
-wait
int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
-signal
int pthread_cond_signal(pthread_cond_t *cond);
-broadcast
int pthread_cond_broadcast(pthread_cond_t *cond);
int pthread_cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr); // attributes --e.g., if it's shared int pthread_cond_destory(pthread_cond_t *cond);
