问为什么在试图锁定来自两个不同进程的共享内存时，pthread_mutex_t分段错误？

EN

//basic version just to test using it between two processes
struct MyLock
{
    public:
        MyLock() {
            pthread_mutexattr_init(&attr);
            pthread_mutexattr_setpshared(&attr, PTHREAD_PROCESS_SHARED);
            pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_ADAPTIVE_NP);

            pthread_mutex_init(&lock, &attr);
        }

        ~MyLock() {
            pthread_mutex_destroy(&lock);
            pthread_mutexattr_destroy(&attr);
        }

        lock() {
            pthread_mutex_lock(&lock);
        }

        unlock() {
            pthread_mutex_unlock(&lock);
        }

    private:
        pthread_mutexattr_t attr;
        pthread_mutex_t lock;
};

void* mem; //some shared memory from shm_open
MyLock* myLock = new(mem) MyLock;
//loop sleeping random amounts and calling ->lock and ->unlock

MyLock* myLock = reinterpret_cast<MyLock*>(mem);
//same loop for locking and unlocking as process A

in pthread_mutex_lock () from /lib64/libpthread.so.0
in MyLock::lock at MyLock.H:50
in Server::setUpSharedMemory at Server.C:59
in Server::Server at Server.C
in main.C:52

{
attr = {
    __size = "\003\000\000\200",
    __align = -2147483645
},
lock = {
    __data = {
      __lock = 1
      __count = 0,
      __owner = 6742, //this is the lightweight process id of a thread in process A
      __nusers = 1,
      __kind = 131,
      __spins = 0,
      __list = {
        __prev = 0x0,
        __Next = 0x0
       }
      },
      __size = "\001\000\000\000\000 //etc,
      __align = 1     
  }
}