1.2.8.1. alpha.unix.BlockInCriticalSection (C)
Check for calls to blocking functions inside a critical section. Applies to: lock, unlock, sleep, getc, fgets, read, recv, pthread_mutex_lock, `` pthread_mutex_unlock, mtx_lock, mtx_timedlock, mtx_trylock, mtx_unlock, lock_guard, unique_lock``

Examples:

void test() {
  std::mutex m;
  m.lock();
  sleep(3); // warn: a blocking function sleep is called inside a critical
            //       section
  m.unlock();
}