assert(pthread_mutexattr_init(&attr) == 0);
assert(pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE) == 0);
assert(pthread_mutex_init(&mesh->mutex, &attr) == 0);
assert(pthread_mutexattr_init(&attr) == 0);
assert(pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE) == 0);
assert(pthread_mutex_init(&mesh->mutex, &attr) == 0);