compiler-rt/test/tsan/annotate_happens_before.cpp

   1 // RUN: %clangxx_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s
   2 #include "test.h"
   3
   4 /*
   5 Annotations usage example.
   6
   7 Tsan does not see synchronization in barrier_wait.
   8 ANNOTATE_HAPPENS_BEFORE/AFTER communicate the synchronization to tsan
   9 and prevent the race report.
  10 */
  11
  12 int Global;
  13
  14 void *Thread1(void *x) {
  15   barrier_wait(&barrier);
  16   ANNOTATE_HAPPENS_AFTER(&barrier);
  17   Global++;
  18   return NULL;
  19 }
  20
  21 void *Thread2(void *x) {
  22   Global--;
  23   ANNOTATE_HAPPENS_BEFORE(&barrier);
  24   barrier_wait(&barrier);
  25   return NULL;
  26 }
  27
  28 int main() {
  29   barrier_init(&barrier, 2);
  30   pthread_t t[2];
  31   pthread_create(&t[0], NULL, Thread1, NULL);
  32   pthread_create(&t[1], NULL, Thread2, NULL);
  33   pthread_join(t[0], NULL);
  34   pthread_join(t[1], NULL);
  35   fprintf(stderr, "DONE\n");
  36   return 0;
  37 }
  38
  39 // CHECK-NOT: WARNING: ThreadSanitizer: data race
  40 // CHECK: DONE
  41