tsan-detector-is-very-basic.cc

#include <stdio.h>
#include <pthread.h>


struct ST {
  pthread_mutex_t mutex;
  char *name;
};


int main(int argc, char **argv) {
  
  ST locks[3];
  for (int i=0; i < 3; ++i) {
    pthread_mutex_init(&locks[i].mutex, NULL);
  }

  printf("Init done\n");

  // Step 1

  pthread_mutex_lock(&locks[0].mutex);
  pthread_mutex_lock(&locks[1].mutex);
  pthread_mutex_unlock(&locks[0].mutex);
  pthread_mutex_unlock(&locks[1].mutex);

  printf("Step 1 done\n");
  // Step 2
  pthread_mutex_lock(&locks[1].mutex);
  pthread_mutex_lock(&locks[0].mutex);
  pthread_mutex_unlock(&locks[1].mutex);
  pthread_mutex_unlock(&locks[0].mutex);
  printf("Step 2 done\n");


  for (int i=0; i < 3; ++i) {
    pthread_mutex_destroy(&locks[i].mutex);
  }

  return 0;
}

Init done
Step 1 done
==================
WARNING: ThreadSanitizer: lock-order-inversion (potential deadlock) (pid=8657)
  Cycle in lock order graph: M6 (0x7ffead0d55d0) => M7 (0x7ffead0d5600) => M6

  Mutex M7 acquired here while holding mutex M6 in main thread:
    #0 pthread_mutex_lock <null> (a.out+0x441816)
    #1 main <null> (a.out+0x4b398d)

    Hint: use TSAN_OPTIONS=second_deadlock_stack=1 to get more informative warning message

  Mutex M6 acquired here while holding mutex M7 in main thread:
    #0 pthread_mutex_lock <null> (a.out+0x441816)
    #1 main <null> (a.out+0x4b39f9)

SUMMARY: ThreadSanitizer: lock-order-inversion (potential deadlock) (/home/psergey/a.out+0x441816) in pthread_mutex_lock
==================
Step 2 done
ThreadSanitizer: reported 1 warnings

Compilation step:

clang++-10 -fsanitize=thread test-asan.cc 
./a.out

Looks like this is a known issue in tsan: google/sanitizers#814

I also asked in the forum: https://llvm.discourse.group/t/threadsanitizer-gives-false-positive-warning-about-deadlock/2483