RE: [PATCH] Fix sporadic failure in g++.dg/tsan/aligned_vs_unaligned_race.C

[Bernd Edlinger <bernd dot edlinger at hotmail dot de>]

Hi Mike,

after some hours of sleep I realized that your step function can do something very interesting,
(which you already requested previously):

That is: create a race condition that is _always_ at 100% missed by tsan:

cat lib.c
/* { dg-do compile } */
/* { dg-options "-O2 -fno-sanitize=all" } */
 
static volatile int serial = 0;
 
void step (int i)
{
  while (__atomic_load_n (&serial, __ATOMIC_ACQUIRE) != i - 1);
  __atomic_store_n (&serial, i, __ATOMIC_RELEASE);
}

cat tiny_race.c 
/* { dg-shouldfail "tsan" } */

#include <pthread.h>

void step(int);

int Global;

void *Thread1(void *x) {
  step (1);
  Global = 42;
  step (3);
  return x;
}

int main() {
  pthread_t t;
  pthread_create(&t, 0, Thread1, 0);
  step (2);
  Global = 43;
  step (4);
  pthread_join(t, 0);
  return Global;
}

/* { dg-output "WARNING: ThreadSanitizer: data race.*(\n|\r\n|\r)" } */



Bernd.