互斥量(互斥锁)
主要应用函数: (1)pthread mutexattr_t mattr //用于定义mutex锁的属性
(2)pthread_mutexattr_init;//初始化一个属性对象
(3)pthread_mutexattr_destroy;
(4)pthread_mutexattr_setpshared //修改mutex的属性;
线程锁:PTHREAA_PROCESS_PRIVATE (进程间私有,即线程锁)
进程锁:PTHREAD_PROCESS_SHARED
思想:mutex定义在mmap进程共享内存中成为共享数据;,把锁的上面属性改为共享即可多进程使用;
代码分析
#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<sys/wait.h>
#include<fcntl.h>
#include<sys/mman.h>
#include<pthread.h>
#include<sys/types.h>
struct md
{
int data;
pthread_mutex_t mutex;
pthread_mutexattr_t attr;
};
int main()
{
struct md *mm;
mm =mmap(NULL,sizeof(mm),PROT_READ | PROT_WRITE,MAP_SHARED|MAP_ANON,-1,0);//创建共享内存
if(mm==MAP_FAILED)
{
perror("mmap error");
exit(1);
}
mm->data=0;
pthread_mutexattr_init(&mm->attr);//将锁设置为进程共享
pthread_mutexattr_setpshared(&mm->attr,PTHREAD_PROCESS_SHARED);
pthread_mutex_init(&mm->mutex,NULL); //初始化锁
pid_t pid = fork();
if(pid == 0)//子进程
{
int i=0;
for(i=0;i<10;i++)
{
pthread_mutex_lock(&mm->mutex);
mm->data++;
printf("-----------chilf data=%d\n",mm->data);
pthread_mutex_unlock(&mm->mutex);
sleep(1);
}
}
else if(pid >0)
{
int i=0;
for(i=0;i<10;i++)
{
pthread_mutex_lock(&mm->mutex);
mm->data +=2;
printf("-----------parent data=%d\n",mm->data);
pthread_mutex_unlock(&mm->mutex);
sleep(1);
}
wait(NULL);
}
exit(1);
}