多线程同步与互斥

1.互斥

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <errno.h>

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
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;
  
  pthread_mutex_init(&mutex,NULL);
  
  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)
    {
      perror("pthread_mutex_lock");
    }
    else
      printf("pthread1:pthread1 lock the variable\n");
    
    for(i=0;i<2;i++)
    {
      sleep(1);
      lock_var++;
    }
    
    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);
  }
}