<>线程-异步通信和同步通信

最新推荐文章于 2025-05-03 16:34:11 发布

原创最新推荐文章于 2025-05-03 16:34:11 发布 · 976 阅读

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本文探讨了并发编程中同步通信的重要性和实现方式，通过使用信号量和线程创建两个实例，展示了如何在多线程环境下实现资源的有效保护。重点介绍了异步通信和同步通信的区别与应用，以及在给定时间限制内如何通过信号量进行线程间的协作与资源访问控制。

《异步通信》

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <errno.h>
//#include <sys/ipc.h>
#include <semaphore.h>

int lock_var;
time_t end_time;
sem_t sem;

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)+30;//终止时间

ret=sem_init(&sem,0,1);
if(ret!=0)
{
  perror("sem_init");
}

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);//等待回收线程
pthread_join(id2,NULL);

exit(0);
}

void pthread1(void *arg)
{
int i;
while(time(NULL) < end_time)
{
  sem_wait(&sem);

  for(i=0;i<2;i++)
  {
//新加printf("wat);
   sleep(1);
   lock_var++;
   printf("lock_var=%d\n",lock_var);
  }

  printf("pthread1:lock_var=%d\n",lock_var);//进行操作，也就是资源保护

  sem_post(&sem);//释放锁
  sleep(1);
}
}

void pthread2(void *arg)
{
// int nolock=0;
//int ret;

while(time(NULL) < end_time)
{
//新加 printf("pthread2:before sem_wait()\n");
  sem_wait(&sem);

  printf("pthread2:pthread2 got lock;lock_var=%d\n",lock_var);

  sem_post(&sem);
  sleep(3);//更改为1
}
}

编译执行时候要助注意：

lsb@ubuntu:~/gx/wangluo$ gcc -g -o sem_num sem_num.c -lpthread

lsb@ubuntu:~/gx/wangluo$ ./sem_num
lock_var=1
lock_var=2
pthread1:lock_var=2
pthread2:pthread2 got lock;lock_var=2
lock_var=3
lock_var=4
pthread1:lock_var=4
pthread2:pthread2 got lock;lock_var=4
lock_var=5
lock_var=6
pthread1:lock_var=6
pthread2:pthread2 got lock;lock_var=6
lock_var=7
lock_var=8
pthread1:lock_var=8
pthread2:pthread2 got lock;lock_var=8

*****************************************************

《同步通信》

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <errno.h>
#include <sys/ipc.h>
#include <semaphore.h>
int lock_var;
time_t end_time;//获取本地时间
sem_t sem1,sem2;

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)+30;
######################################给线程，分配那些可执行文件###################################
ret=sem_init(&sem1,0,1);
ret=sem_init(&sem2,0,0);
if(ret!=0)
{
  perror("sem_init");
}
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){
  sem_wait(&sem2);//进行2P操作
  for(i=0;i<2;i++){
   sleep(1);
   lock_var++;
   printf("lock_var=%d\n",lock_var);
  }
  printf("pthread1:lock_var=%d\n",lock_var);
  sem_post(&sem1);//通知1，进行V操作
  sleep(1);
}
}

void pthread2(void *arg)
{
//int nolock=0;
//int ret;
while(time(NULL) < end_time){
sem_wait(&sem1);
printf("pthread2:pthread1 got lock;lock_var=%d\n",lock_var);
sem_post(&sem2);
sleep(3);
}
}

执行：
lsb@ubuntu:~/gx/wangluo$ gcc -o sem_syn sem_syn.c -lpthread

lsb@ubuntu:~/gx/wangluo$ ./sem_syn
pthread2:pthread1 got lock;lock_var=0
lock_var=1
lock_var=2
pthread1:lock_var=2
pthread2:pthread1 got lock;lock_var=2
lock_var=3
lock_var=4
pthread1:lock_var=4
pthread2:pthread1 got lock;lock_var=4
lock_var=5
lock_var=6
pthread1:lock_var=6
pthread2:pthread1 got lock;lock_var=6
lock_var=7
lock_var=8
pthread1:lock_var=8
pthread2:pthread1 got lock;lock_var=8