unique_lock加锁defer_lock

#include <iostream>
#include <mutex>
#include <thread>

void msg_func()
{
   std::mutex mutex;
   while(1)
   {
      std::unique_lock<std::mutex> unique(mutex, std::defer_lock);
      unique.lock();

      std::cout << "do something" << std::endl;

      std::chrono::milliseconds second(1000);
      std::this_thread::sleep_for(second);
   }
}

int main()
{
   std::thread mythread(&msg_func);
   getchar();

   return 0;
}

$ g++ unique_lock_defer.cpp -std=c++11 -pthread 

$ ./a.out 
do something
do something

注：
defer_lock创建一个没有加锁的mutex