testcancel.c

让你了解Unix进程间的通信是如何实现的

#include	"unpipc.h"
#include	"pthread_rwlock.h"

pthread_rwlock_t	rwlock = PTHREAD_RWLOCK_INITIALIZER;

void	 *thread1(void *), *thread2(void *);
pthread_t	tid1, tid2;

int
main(int argc, char **argv)
{
	void	*status;
	Pthread_rwlock_init(&rwlock, NULL);

	Set_concurrency(2);
	Pthread_create(&tid1, NULL, thread1, NULL);
	sleep(1);		/* let thread1() get the lock */
	Pthread_create(&tid2, NULL, thread2, NULL);

	Pthread_join(tid2, &status);
	if (status != PTHREAD_CANCELED)
		printf("thread2 status = %p\n", status);
	Pthread_join(tid1, &status);
	if (status != NULL)
		printf("thread1 status = %p\n", status);

	printf("rw_refcount = %d, rw_nwaitreaders = %d, rw_nwaitwriters = %d\n",
		   rwlock.rw_refcount, rwlock.rw_nwaitreaders,
		   rwlock.rw_nwaitwriters);
	Pthread_rwlock_destroy(&rwlock);
		/* 4returns EBUSY error if cancelled thread does not cleanup */

	exit(0);
}

void *
thread1(void *arg)
{
	Pthread_rwlock_rdlock(&rwlock);
	printf("thread1() got a read lock\n");
	sleep(3);		/* let thread2 block in pthread_rwlock_wrlock() */
	pthread_cancel(tid2);
	sleep(3);
	Pthread_rwlock_unlock(&rwlock);
	return(NULL);
}

void *
thread2(void *arg)
{
	printf("thread2() trying to obtain a write lock\n");
	Pthread_rwlock_wrlock(&rwlock);
	printf("thread2() got a write lock\n");
	sleep(1);
	Pthread_rwlock_unlock(&rwlock);
	return(NULL);
}