#include "apue.h"
#include <pthread.h>

pthread_mutex_t lock1 = PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_t lock2 = PTHREAD_MUTEX_INITIALIZER;

void
prepare(void)
{
	printf("preparing locks...\n");
	pthread_mutex_lock(&lock1);
	pthread_mutex_lock(&lock2);
}

void
parent(void)
{
	printf("parent unlocking locks...\n");
	pthread_mutex_unlock(&lock1);
	pthread_mutex_unlock(&lock2);
}

void
child(void)
{
	printf("child unlocking locks...\n");
	pthread_mutex_unlock(&lock1);
	pthread_mutex_unlock(&lock2);
}

void *
thr_fn(void *arg)
{
	printf("thread started...\n");
	pause();
	return(0);
}

int
main(void)
{
	int			err;
	pid_t		pid;
	pthread_t	tid;

#if defined(BSD) || defined(MACOS)
	printf("pthread_atfork is unsupported\n");
#else
	if ((err = pthread_atfork(prepare, parent, child)) != 0)
		err_exit(err, "can't install fork handlers");
	err = pthread_create(&tid, NULL, thr_fn, 0);
	if (err != 0)
		err_exit(err, "can't create thread");
	sleep(2);
	printf("parent about to fork...\n");
	if ((pid = fork()) < 0)
		err_quit("fork failed");
	else if (pid == 0)	/* child */
		printf("child returned from fork\n");
	else		/* parent */
		printf("parent returned from fork\n");
#endif
	exit(0);
}