12.3 进程和线程传递数据、多线程编程

　　我们在进程中给线程传递数据，程序如下：

#include <unistd.h>
#include <sys/types.h>

#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <pthread.h>
/*
int pthread_create(pthread_t *restrict thread,
           const pthread_attr_t *restrict attr,
           void *(*start_routine)(void*), void *restrict arg);
*/

int g_num = 0;
typedef struct _Teacher
{
    char name[64];
    int age;
}Teacher;

void *start_routine(void *arg)
{
    int i = 0;
    Teacher *pt = (Teacher *)arg;
    printf("name : %s
", pt->name);
    printf("age : %d
", pt->age);
    
    pthread_detach(pthread_self());
    
    printf("thread id = %lu
", pthread_self());
    
    for(i = 0; i < 10; i++)
    {
        printf("B");
        fflush(stdout);
    }
    
    sleep(3);
    
    printf("
");
    
    pthread_exit(NULL);
}

int main()
{
    pthread_t thread;
    int i = 0;
    
    g_num = 10;
    
    Teacher t = {"zhang", 10};
    
    pthread_create(&thread, NULL, start_routine, &t);
    
    for(i = 0; i< 10; i++)
    {
        printf("A");
        fflush(stdout);
    }
    printf("
");
    
    pthread_join(thread, NULL);
    printf("child thread die
");
    
    return 0;
}

执行结果如下：

从线程体中将数据传出来，通过pthread_exit函数，程序如下：

#include <unistd.h>
#include <sys/types.h>

#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <pthread.h>
/*
int pthread_create(pthread_t *restrict thread,
           const pthread_attr_t *restrict attr,
           void *(*start_routine)(void*), void *restrict arg);
*/

int g_num = 0;
typedef struct _Teacher
{
    char name[64];
    int age;
}Teacher;

void *start_routine(void *arg)
{
    int i = 0;
    Teacher *pt = (Teacher *)arg;
    printf("name : %s
", pt->name);
    printf("age : %d
", pt->age++);
    
    pthread_detach(pthread_self());
    
    for(i = 0; i < 10; i++)
    {
        printf("B");
        fflush(stdout);
    }
    
    sleep(2);
    
    printf("
");
    
    pthread_exit(arg);
}

int main()
{
    pthread_t thread;
    int i = 0;
    
    g_num = 10;
    
    Teacher t = {"zhang", 10};
    
    pthread_create(&thread, NULL, start_routine, &t);
    
    for(i = 0; i< 10; i++)
    {
        printf("A");
        fflush(stdout);
    }
    printf("
");
    
    Teacher *p = NULL;
    
    pthread_join(thread, (void **)&p);
    printf("name : %s
", p->name);
    printf("age : %d
", p->age);
    
    return 0;
}

第41行将arg传出来了（41行使用return arg是一样的），执行结果如下：

注意：线程体函数中传出的数据不能是在线程体中的局部变量。

一般情况下，线程的运算结果需要告诉父进程，即可用这种方法传出来。

多线程编程：

 

父进程传给每个子线程的地址空间必须是独立的，否则当多个线程访问这些地址空间时会造成相互影响，例如A空间传给了线程a，在主进程中修改A空间时，就会影响进程a。

线程属性设置：

 POSIX线程锁：线程也可以用信号量作为锁，但是信号量动作太大，线程有自己的锁机制。

多线程加锁的程序如下：

#include <unistd.h>
#include <sys/types.h>

#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <pthread.h>
/*
int pthread_mutex_init(pthread_mutex_t *restrict mutex,
           const pthread_mutexattr_t *restrict attr);
       pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER; 
       
int pthread_mutex_destroy(pthread_mutex_t *mutex);
       int pthread_mutex_init(pthread_mutex_t *restrict mutex,
           const pthread_mutexattr_t *restrict attr);
       pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
*/

typedef struct _ThreadInfo
{
    char id[100];
    int port;
    char name[64];
    int age;
    int numId;
}ThreadInfo;

int g_num = 0;
int nNum;
int nLoop;

/*
int pthread_mutex_lock(pthread_mutex_t *mutex);
       int pthread_mutex_trylock(pthread_mutex_t *mutex);
       int pthread_mutex_unlock(pthread_mutex_t *mutex);

*/

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

void *thread_routine(void *arg)
{
    int i = 0;
    ThreadInfo *tmp = (ThreadInfo *)arg;
    pthread_mutex_lock(&mutex);
    
    printf("g_num : %d 
", g_num);
    sleep(1);
    printf("numId : %d 
", tmp->numId);
    
    pthread_mutex_unlock(&mutex);
    /*
    for(i = 0; i < nLoop; i++)
    {
        printf("thread id:%d  loop : %d  numid : %d 
", pthread_self(), i, tmp->numId);
    }
    */
    if(tmp != NULL)
    {
        free(tmp);
    }
    
    pthread_exit(0);
}


int main()
{
    int i = 0;
    nNum = 10;
    nLoop = 10;
    
    pthread_t tidArray[200];
    g_num = 11;
    
    //pthread_mutex_init(&mutex, NULL);
    
    printf("enter the number of thread : 
");
    scanf("%d", &nNum);
    
    printf("enter thr loop : 
");
    scanf("%d", &nLoop);
    
    for (i = 0; i < nNum; i++)
    {
        ThreadInfo *p = (ThreadInfo *)malloc(sizeof(ThreadInfo));
        p->numId = i + 1;
        pthread_create(&tidArray[i], NULL, thread_routine, (void *)p);
    }
    
    for(i = 0; i < nNum; i++)
    {
        pthread_join(tidArray[i], NULL);
    }
    
    printf("end 
");
    
    return 0; 
}

第40行是锁的静态初始化，第77行是锁的动态初始化。

执行结果如下：

测试多线程的四种情况：