add sleeper, to reduce cpu usage.

lichao

2021-05-20 6b96ee857e366af317ab9dc1b6b4f9c22576e83b

 src/shm.cpp

@@ -25,6 +25,7 @@
    mshm_t(open_or_create, name.c_str(), size, 0, AllowAll()),
    name_(name)
{
   pmutex_ = FindOrCreate<Mutex>("ShmSelfControlMutex0");
}

SharedMemory::~SharedMemory()