Linux操作系统多线程同步Mutex详细介绍

#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;
time_t end_time;
int sum;

void pthread1(void *arg);
void pthread2(void *arg);
void pthread3(void *arg);

int main(int argc, char *argv[])
{
pthread_t id1,id2,id3;
pthread_t mon_th_id;
int ret;
sum=10;

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");

ret=pthread_create(&id3,NULL,(void *)pthread3, NULL);
if(ret!=0)
perror("pthread cread3");

pthread_join(id1,NULL);
pthread_join(id2,NULL);
pthread_join(id3,NULL);
exit(0);
}

void pthread1(void *arg)
{
int i;
while(time(NULL) < end_time)
{
if(pthread_mutex_lock(&mutex)!=0) //lock
{
perror("pthread_mutex_lock");
}
else
printf("pthread1:pthread1 lock the variable\n");
for(i=0;i<2;i++)
{
sleep(2);
lock_var++;
}
if(pthread_mutex_unlock(&mutex)!=0) //unlock
{
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);//try lock
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)//unlock
{
perror("pthread_mutex_unlock");
}
else
printf("pthread2:pthread2 unlock the variable\n");
}
sleep(1);
}
}



void pthread3(void *arg)
{/*
int nolock=0;
int ret;
while(time(NULL) < end_time)
{
ret=pthread_mutex_trylock(&mutex);
if(ret==EBUSY)
printf("pthread3:the variable is locked by pthread1 or 2\n");
else
{
if(ret!=0)
{
perror("pthread_mutex_trylock");
exit(1);
}
else
printf("pthread3:pthread3 got lock.The variable is %d\n",lock_var);
if(pthread_mutex_unlock(&mutex)!=0)
{
perror("pthread_mutex_unlock");
}
else
printf("pthread3:pthread2 unlock the variable\n");
}
sleep(3);
}*/
}