#include <pthread.h>

pthread_spinlock_t spinlock;

void*
thr_routine(void *arg)
{
	int i;

	for (i = 0; i < 10; ++i) {
		pthread_spin_lock(&spinlock);
		printf("I am %d\n", (int)arg);
		sleep(1);
		pthread_spin_unlock(&spinlock);
	}
	printf("thread %d exits\n", (int)arg);
	return (0);
}

void*
thr_routine2(void *arg)
{
	int i;

	for (i = 0; i < 10; ++i) {
		while (pthread_spin_trylock(&spinlock))
			;
		printf("I am %d (trylock)\n", (int) arg);
		sleep(1);
		pthread_spin_unlock(&spinlock);
	}
	printf("thread %d exits. (trylock)\n", (int)arg);
	return (0);
}

int main()
{
	pthread_t td1, td2, td3, td4;

	if (pthread_spin_init(&spinlock, PTHREAD_PROCESS_PRIVATE))
		errx(1, "error init spinlock\n");

	pthread_create(&td1, NULL, thr_routine, (void *)1);
	pthread_create(&td2, NULL, thr_routine, (void *)2);
	pthread_create(&td3, NULL, thr_routine, (void *)3);
	pthread_create(&td4, NULL, thr_routine2, (void *)4);
		
	pthread_join(td1, NULL);
	pthread_join(td2, NULL);
	return (0);
}