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#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <assert.h>
#include <pthread.h>
static int nthread = 1;
static int round = 0;
struct barrier {
pthread_mutex_t barrier_mutex;
pthread_cond_t barrier_cond;
int nthread; // Number of threads that have reached this round of the barrier
int round; // Barrier round
} bstate;
static void
barrier_init(void)
{
assert(pthread_mutex_init(&bstate.barrier_mutex, NULL) == 0);
assert(pthread_cond_init(&bstate.barrier_cond, NULL) == 0);
bstate.nthread = 0;
}
static void
barrier()
{
// Block until all threads have called barrier() and
// then increment bstate.round.
pthread_mutex_lock(&bstate.barrier_mutex);
bstate.nthread++;
if(bstate.nthread != nthread) {
pthread_cond_wait(&bstate.barrier_cond, &bstate.barrier_mutex);
} else {
pthread_cond_broadcast(&bstate.barrier_cond);
// All threads have reached barrier.
// reset and increase round
bstate.nthread = 0;
bstate.round++;
}
pthread_mutex_unlock(&bstate.barrier_mutex);
}
static void *
thread(void *xa)
{
long n = (long) xa;
long delay;
int i;
for (i = 0; i < 20000; i++) {
int t = bstate.round;
assert (i == t);
barrier();
usleep(random() % 100);
}
return 0;
}
int
main(int argc, char *argv[])
{
pthread_t *tha;
void *value;
long i;
double t1, t0;
if (argc < 2) {
fprintf(stderr, "%s: %s nthread\n", argv[0], argv[0]);
exit(-1);
}
nthread = atoi(argv[1]);
tha = malloc(sizeof(pthread_t) * nthread);
srandom(0);
barrier_init();
for(i = 0; i < nthread; i++) {
assert(pthread_create(&tha[i], NULL, thread, (void *) i) == 0);
}
for(i = 0; i < nthread; i++) {
assert(pthread_join(tha[i], &value) == 0);
}
printf("OK; passed\n");
}
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