/*! Simple semaphore example with sem_wait/sem_post interface */

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <semaphore.h>

#define THREADS  6
static pthread_spinlock_t lock;
static int work_in_progress = 1;

static void *worker ( void *p )
{
	long id = (long) p;
	struct timespec t = { id, 0 };

	printf ( "Thread %ld starting\n", id );

	while ( work_in_progress ) {
		pthread_spin_lock ( &lock );

		printf ( "Thread %ld inside C.S.\n", id );

		nanosleep ( &t, NULL );

		printf("Thread %ld leaving C.S.\n", id);

		pthread_spin_unlock ( &lock );

		nanosleep ( &t, NULL );
	}

	printf ( "Thread %ld exiting\n", id );

	return NULL;
}

int main ()
{
	long i;
	pthread_t thr[THREADS];
	struct timespec t = { 50, 0 };

	pthread_spin_init ( &lock, PTHREAD_PROCESS_PRIVATE );

	for ( i = 0; i < THREADS; i++ )
		pthread_create ( &thr[i], NULL, worker, (void *) i+1 );

	nanosleep ( &t, NULL );

	work_in_progress = 0;

	for ( i = 0; i < THREADS; i++ )
		pthread_join ( thr[i], NULL );

	return 0;
}

/* Example run:
$ gcc pthread_spin_lock.c -pthread -Wall
$ ./a.out
Thread 6 starting
Thread 6 inside C.S.
Thread 5 starting
Thread 4 starting
Thread 3 starting
Thread 2 starting
Thread 1 starting
Thread 6 leaving C.S.
Thread 2 inside C.S.
Thread 2 leaving C.S.
Thread 1 inside C.S.
Thread 1 leaving C.S.
Thread 5 inside C.S.
...
*/