学步园

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <errno.h>
//1.静态初始化，当动态初始化时，屏蔽静态初始化
//pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

//2.动态初始化

pthread_mutex_t mutex;
int lock_var = 0;
time_t end_time;

void pthread1(void *arg);
void pthread2(void *arg);

int main(int argc, char *argv[])
{
 pthread_t id1,id2;
 //pthread_t mon_th_id;
 int ret;

 end_time = time(NULL)+10;
 
                                         //2.动态初始化，待确认释放存在
 pthread_mutex_init(&mutex,NULL);//动态初始化PTHREAD_MUTEX_INITIALIZER
 
 ret=pthread_create(&id1,NULL,(void *)pthread1, NULL);
 if(ret!=0)
  perror("pthread cread1");
 
 ret=pthread_create(&id2,NULL,(void *)pthread2, NULL);
 if(ret!=0)
  perror("pthread cread2");
 
 pthread_join(id1,NULL);
 pthread_join(id2,NULL);
 
 exit(0);
}

void pthread1(void *arg)
{
 int i;
 while(time(NULL) < end_time)
 {
  if(pthread_mutex_lock(&mutex)!=0)//申请锁
  {
   perror("pthread_mutex_lock");
  }
  else//以下为临界区
   printf("pthread1:pthread1 lock the variable\n");
  
  for(i=0;i<2;i++)
  {
   sleep(1);//工程时候，不能用睡眠时间，加锁时间越短越好
   lock_var++;
  }//以上临界区
  
  if(pthread_mutex_unlock(&mutex)!=0)
  {
   perror("pthread_mutex_unlock");
  }
  else
   printf("pthread1:pthread1 unlock the variable\n");
  
  sleep(1);
 }
}

void pthread2(void *arg)
{
// int nolock=0;
 int ret;
 
 while(time(NULL) < end_time)
 {
  ret=pthread_mutex_trylock(&mutex);
  if(ret==EBUSY)
   printf("pthread2:the variable is locked by pthread1\n");
  else
  {
   if(ret!=0)
   {
    perror("pthread_mutex_trylock");
    exit(1);
   }
   else
    printf("pthread2:pthread2 got lock.The variable is %d\n",lock_var);
   if(pthread_mutex_unlock(&mutex)!=0)
   {
    perror("pthread_mutex_unlock");
   }
    else
    printf("pthread2:pthread2 unlock the variable\n");
  }
  sleep(3);
 }
}

 执行：

lsb@ubuntu:~/gx/wangluo$ gcc -o mutex mutex.c -lpthread
lsb@ubuntu:~/gx/wangluo$ ./mutex
pthread1:pthread1 lock the variable
pthread2:the variable is locked by pthread1
pthread1:pthread1 unlock the variable
pthread2:pthread2 got lock.The variable is 2
pthread2:pthread2 unlock the variable
pthread1:pthread1 lock the variable
pthread1:pthread1 unlock the variable
pthread2:pthread2 got lock.The variable is 4
pthread2:pthread2 unlock the variable
pthread1:pthread1 lock the variable
pthread1:pthread1 unlock the variable
pthread2:pthread2 got lock.The variable is 6
pthread2:pthread2 unlock the variable
pthread1:pthread1 lock the variable
pthread1:pthread1 unlock the variable