1// RUN: %clang_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s
2// CHECK-NOT: ThreadSanitizer: data race
3// CHECK: DONE
4
5#include <stdio.h>
6#include <stdlib.h>
7#include <pthread.h>
8#include <unistd.h>
9
10const int kSize = 4;
11volatile int kIter = 10;  // prevent unwinding
12int data[2][kSize];
13pthread_barrier_t barrier;
14
15void *thr(void *p) {
16  int idx = (int)(long)p;
17  for (int i = 0; i < kIter; i++) {
18    int *prev = data[i % 2];
19    int *curr = data[(i + 1) % 2];
20    int left = idx - 1 >= 0 ? prev[idx - 1] : 0;
21    int right = idx + 1 < kSize ? prev[idx + 1] : 0;
22    curr[idx] = (left + right) / 2;
23    pthread_barrier_wait(&barrier);
24  }
25  return 0;
26}
27
28int main() {
29  pthread_barrier_init(&barrier, 0, kSize);
30  pthread_t th[kSize];
31  for (int i = 0; i < kSize; i++)
32    pthread_create(&th[i], 0, thr, (void*)(long)i);
33  for (int i = 0; i < kSize; i++)
34    pthread_join(th[i], 0);
35  pthread_barrier_destroy(&barrier);
36  fprintf(stderr, "DONE\n");
37}
38