stdthread并发recursive_mutex 递归锁

Posted 2022-04-01 thefist11

1. 使用场景：死锁

MutexLock mutex;  

void foo()  
  
    mutex.lock();  
    // do something  
    mutex.unlock();  
  

void bar()  
  
    mutex.lock();  
    // do something  
    foo();  
    mutex.unlock();   
  

1.1 解决方案

#include <iostream>
#include <thread>
#include <mutex>
 
class X 
    std::recursive_mutex m;
    std::string shared;
  public:
    void fun1() 
      std::lock_guard<std::recursive_mutex> lk(m);
      shared = "fun1";
      std::cout << "in fun1, shared variable is now " << shared << '\\n';
    
    void fun2() 
      std::lock_guard<std::recursive_mutex> lk(m);
      shared = "fun2";
      std::cout << "in fun2, shared variable is now " << shared << '\\n';
      fun1(); // ① 递归锁在此处变得有用
      std::cout << "back in fun2, shared variable is " << shared << '\\n';
    ;
;
 
int main() 

    X x;
    std::thread t1(&X::fun1, &x);
    std::thread t2(&X::fun2, &x);
    t1.join();
    t2.join();