49 lines
1.2 KiB
C
49 lines
1.2 KiB
C
#include <pthread.h>
|
|
#include <inttypes.h>
|
|
#include <assert.h>
|
|
#include <stdio.h>
|
|
#include <stdatomic.h>
|
|
|
|
#define RUNS (4096 * 256)
|
|
#define THREADS 4
|
|
|
|
static atomic_int leader[RUNS] = { 0 };
|
|
static atomic_int nb_leaders[RUNS] = { 0 }; // used to check correctness
|
|
|
|
void* elect(void* _tid) {
|
|
intptr_t tid = (intptr_t) _tid;
|
|
for (int r = 0; r < RUNS; r++) {
|
|
int expected = 0;
|
|
if (atomic_compare_exchange_strong(&leader[r], &expected, tid)) {
|
|
atomic_fetch_add(&nb_leaders[r], 1); // used to check correctness
|
|
}
|
|
// **Correct**, we use the Compare and Swap operation to atomically check if
|
|
// a leader has already been elected and if not, we impose ourselves. :)
|
|
}
|
|
}
|
|
|
|
int main() {
|
|
pthread_t handlers[THREADS];
|
|
|
|
for (intptr_t i = 0; i < THREADS; i++) {
|
|
int res = pthread_create(&handlers[i], NULL, elect, (void*)(i + 1));
|
|
assert(!res);
|
|
}
|
|
|
|
for (int i = 0; i < THREADS; i++) {
|
|
int res = pthread_join(handlers[i], NULL);
|
|
assert(!res);
|
|
}
|
|
|
|
int r = 0;
|
|
for (; r < RUNS; r++) {
|
|
if (nb_leaders[r] != 1) {
|
|
printf("Leader election for round %d failed.\n", r);
|
|
break;
|
|
}
|
|
}
|
|
if (r == RUNS) {
|
|
printf("Looks correct to me! :)\n");
|
|
}
|
|
}
|