/* atomic-shm.c
 * gcc -O -o atomic-shm atomic-shm.c
 */

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/wait.h>

#define COUNT		(10000000)

static void
atomic_inc (volatile int *count)
{
	int t0;

	asm volatile (
		"1:	\n\t"
		"ll	%[t0], %[count] \n\t"
		"addiu	%[t0], 1 \n\t"
		"sc	%[t0], %[count] \n\t"
		"beqz	%[t0], 1b \n\t"
		"sync	\n\t"
		:[t0]"+&r"(t0)
		:[count]"m"(*count)
	);
}

int
main (int argc, char *argv[])
{
	int i;
	pid_t pid;
	void *p;

	p = mmap (NULL, 16384, PROT_READ | PROT_WRITE,
				MAP_SHARED | MAP_ANONYMOUS, -1, 0);
	if (MAP_FAILED == p) {
		fprintf (stderr, "Map shared file failed!\n");
		return -1;
	}

	pid = fork ();
	if (-1 == pid) {
		fprintf (stderr, "Fork failed!\n");
		return -2;
	}

	for (i=0; i<COUNT; i++) {
		atomic_inc ((volatile int *) p);
	}

	if (pid) {
		if (-1 == waitpid (pid, NULL, 0)) {
			fprintf (stderr, "Wait child failed!\n");
			return -3;
		}
		printf ("%s\n", ((2 * COUNT) == *(volatile int *) p) ?
					"PASS" : "FAIL");
	}

	munmap (p, 16384);

	return 0;
}