线程安全,读写锁

多线程不能调用strtok函数，它内部是用一个静态全局变量来记住当前位置，所以在main函数结束之前，线程和主函数用的是一个strtok,因此是错误的，下面是错误的代码。

#include<stdio.h>
#include<stdlib.h>
#include<>string.h
#include<semaphore.h>
#include<pthread.h>

void* fun(void* arg)
{
    char arr[128]={"1 2 3 4 5 6 7 8 9"};
    char* s=strtok(arr," ");
    while(s!=NULL)
    {
        printf("fun s=%s\n",s);
        sleep(1);
        s=strtok(NULL," ");
    }
}


int main()
{
   pthread_t id;
   pthread_create(&id,NULL,fun,NULL);
char buf[128]={"a b c d e f g h"};
char* s=strtok(buff," ");
while(s!=NULL)
{
    printf("main s=%s\n",s);
    sleep(1);
    s=strtok(NULL," ");
}
pthread_join(id,NULL);
exit(0);
}

strtok_r是为了解决上面的问题实现的，各自记住各自分割在哪

#include<stdio.h>
#include<stdlib.h>
#include<>string.h
#include<semaphore.h>
#include<pthread.h>

void* fun(void* arg)
{
    char arr[128]={"1 2 3 4 5 6 7 8 9"};
    char* ptr=NULL;
    char* s=strtok_r(arr," ",&ptr);将指针ptr传进去改变指向的位置
    while(s!=NULL)
    {
        printf("fun s=%s\n",s);
        sleep(1);
        s=strtok_r(NULL," "，&ptr);
    }
}


int main()
{
   pthread_t id;
   pthread_create(&id,NULL,fun,NULL);
char buf[128]={"a b c d e f g h"};
char* ptr=NULL;
char* s=strtok_r(buff," ",&ptr);
while(s!=NULL)
{
    printf("main s=%s\n",s);
    sleep(1);
    s=strtok_r(NULL," ",&ptr);
}
pthread_join(id,NULL);
exit(0);
}

读写锁

读写锁可以共享读，而互斥锁不可以。

#include<stdio.h>
#include<string.h>
#include<pthread.h>
#include<unistd.h>

pthread_rwlock_t rwlock;

void* read_fun1(void* arg)
{
     while(1)
     {
     pthread_rwlock_rdlock(&rwlock);读锁
         printf("read1 start\n");
         sleep(1);
         printf("read1 end\n");
         pthread_rwlock_unlock(&rwlock);
         sleep(1);
     }
}

void* read_fun2(void*)
{
    while(1)
    {
       pthraed_rwlock_rdlock(&rwlock);
       printf("read2 start\n");
       sleep(1);
       printf("read2 end\n");
       pthread_rwlock_unlock(&rwlock);
       sleep(1);
    }
}

void* write_fun(void* arg)
{
  while(1)
  {
    pthread_rwlock_wrlock(&rwlock);
     printf("write start\n");
     sleep(3);
     printf("write end\n");
     pthread_rwlock_unlock(&rwlock);
     sleep(1);
  }
}


int main()
{
    pthread_rwlock_init(&rwlock,NULL);
    pthread_t idr1,idr2;
    pthread_create(&idr1,NULL,read_fun1,NULL);
    pthread_create(&idr2,NULL,read_fun2,NULL);
    pthread_create(&idw,NULL,write_fun,NULL);
    
pthread_join(idr1,NULL);
pthread_join(idr2,NULL);
pthread_join(idw,NULL);
pthread_rwlock_destroy(&rwlock);
}

标签：rwlock,include,strtok,读写,printf,安全,线程,pthread,NULL
来源： https://blog.csdn.net/weixin_48569863/article/details/121583132