/* Trivial test case of __exchange_and_add() from gcc stdlibc's atomicity.h */
#ifdef __i386__
/* red hat */
//#include <i386-redhat-linux/bits/atomicity.h>
/* debian */
#include <i386-linux/bits/atomicity.h>
#endif
#ifdef powerpc
#include <powerpc-linux/bits/atomicity.h>
#endif

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

#define NTHREADS 8
#define NLOOPS 100000
#define NREPEATS 100

int g_tail;
unsigned char g_buf[NTHREADS * NLOOPS];
#define UNINITIALIZED_VAL ((sizeof(g_buf[0])<<8)-1)

void fail(int line) { printf("FAIL in line %d\n", line); exit(1); }

#define FAIL() fail(__LINE__)

/* Add NLOOPS to g_tail */
void *add_num(void* arg)
{
	int i;
	char me = (int) arg;

	for (i=0; i<NLOOPS; i++) {
		int oldtail = __exchange_and_add(&g_tail, 1);
		/* Record which thread grabbed this byte of the buf */
		g_buf[oldtail] = me;
	}
	return NULL;
}

int main(int argc, char **argv)
{
	int repeat;
	int switches = 0;
	time_t t0 = time(0);

	printf("nthreads %d, nloops %d, nrepeats %d\n", NTHREADS, NLOOPS, NREPEATS);
	if (NTHREADS > UNINITIALIZED_VAL)
		FAIL();
	for (repeat=0; repeat < NREPEATS; repeat++) {
		pthread_t thread[NTHREADS];
		int i;
		int curthread;
		memset(g_buf, UNINITIALIZED_VAL, sizeof(g_buf));
		g_tail = 0;

		for (i=0; i<NTHREADS; i++)
			if (pthread_create(&thread[i], NULL, add_num, (void *)i))
				FAIL();
		for (i=0; i<NTHREADS; i++)
			if (pthread_join(thread[i], NULL))
				FAIL();

		if (g_tail != NTHREADS*NLOOPS) {
			printf("sum: %i\n", g_tail);
			FAIL();
		}

		/* look for holes in buf.  Also count 'context switches'. */
		curthread = -1;
		for (i=NTHREADS*NLOOPS-1; i>=0; i--) {
			if (g_buf[i] == UNINITIALIZED_VAL)
				FAIL();
			if (g_buf[i] != curthread) {
				curthread = g_buf[i];
				switches++;
			}
		}
	}
	printf("%d context switches in %d seconds\n", switches, time(0)-t0);

	printf("PASS\n");
	return 0;
}