list8-1.cpp

来自「这是c++编程方面的名著的例子代码」· C++ 代码 · 共 71 行

// Listing 8-1
// This program demonstrates the improper use
// use of a global mutex to protect a object
// two threads

#include <iostream.h>
#include <pthread.h>
#include <mtration.h>
#include <math.h>

rational Number;
pthread_mutex_t Mutex = PTHREAD_MUTEX_INITIALIZER;

void *threadA(void *X)
{
    long int Q;
    try{
         for(Q =2; Q < 500;Q += 4)
         {   
             pthread_mutex_lock(&Mutex);
             Number.assign((Q/2),Q);
             cout << pthread_self() << " Thread A: " << Number << endl;
             pthread_mutex_unlock(&Mutex);
         }
    }
    catch(general_exception &M)
    {
      cout << pthread_self() << M.message() << endl;
    }                 
}

//Thread B is not cooperating with the proper
// use of Mutex protection for the rational object 'Number'.

void *threadB(void *X)
{
   long int Y;
   try{
       for(Y = 5;Y < 500;Y += 5){
           Number.assign((Y/5),Y);
           cout << pthread_self() << " Thread B " << *Number << endl;          
       }  
   }
   catch(general_exception &M)
   {
       cout << pthread_self() << M.message() << endl;
   }
}


void main(void)
{
    pthread_t ThreadA;
    pthread_t ThreadB;  
    pthread_create(&ThreadA,NULL,threadA,NULL);
    pthread_create(&ThreadB,NULL,threadB,NULL);       
    pthread_join(ThreadA,NULL);
    pthread_join(ThreadB,NULL);
    pthread_mutex_destroy(&Mutex);   
}