Unix/Linux 编程:多线程编程

之前已经用过不少在Windows和C++上多多线程编程技术来。

在Linux上原理大致和Windows是相同多。主要多区别在于了解POSIX规范和一些API

参考文档：http://www.cnblogs.com/skynet/archive/2010/10/30/1865267.html

实际上笔者认为创建线程池和使用epoll（windows上的完成端口）可能更适合开发商用应用程序。但是还是需要理解线程同步多本质。

有关线程操作的函数

#include <pthread.h>

int pthread_create(pthread_t *tid, const pthread_attr_t *attr, void *(*func) (void *), void *arg);
int pthread_join (pthread_t tid, void ** status);
pthread_t pthread_self (void);
int pthread_detach (pthread_t tid);
void pthread_exit (void *status);

/*
是否熟悉POSIX多线程编程技术？如熟悉，编写程序完成如下功能：
1）有一int型全局变量g_Flag初始值为0；
2）在主线称中起动线程1，打印“this is thread1”，并将g_Flag设置为1
3）在主线称中启动线程2，打印“this is thread2”，并将g_Flag设置为2
4）线程序1需要在线程2退出后才能退出
5）主线程在检测到g_Flag从1变为2，或者从2变为1的时候退出
*/

/* File: mt.c
multithread demo
*/

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

// global variable.
int g_Flag = 0;
static pthread_mutex_t  mutex   = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t   cond    = PTHREAD_COND_INITIALIZER;

// thread function 1
void * thread1(void* );
// thread function 2
void * thread2(void* );

/*
* when the process is initialized, the main thread is creatd by auto.
* So we just need to create two children thread.
*/
int main(int argc, char ** argv)
{
printf("Enter main thread.\n");
pthread_t tid1, tid2;
int rc1 = 0, rc2 = 0;
// create the thread2
rc2 = pthread_create(&tid2, NULL, thread2, NULL);
if(rc2 != 0)
printf("%s: %s\n", __func__, strerror(rc2));

// create the thread1
rc1 = pthread_create(&tid1, NULL, thread1, &tid2);
if(rc1 != 0)
printf("%s: %s\n", __func__, strerror(rc1));

pthread_cond_wait(&cond, &mutex);
printf("Leave main thread.\n");

exit(0);
}

/*
* thread1() will execute by pthread_Create
* it will set g_Flag = 1.
*/
void * thread1(void * arg)
{
printf("Enter thread1.\n");
printf("this is thread1, g_Flag: %d, thread id is %u.\n",
g_Flag, (unsigned int)pthread_self());

pthread_mutex_lock(&mutex);
if(g_Flag == 2)
pthread_cond_signal(&cond);
g_Flag = 1;
printf("this is thread1, g_Flag: %d, thread id is %u.\n",
g_Flag, (unsigned int)pthread_self());

pthread_mutex_unlock(&mutex);
// wait for the thread2 to be exited at first.
pthread_join(*(pthread_t *)arg, NULL);
printf("Leave thread1.\n");
pthread_exit(0);
}

/*
* thread2() will execute by pthread_Create
* it will set g_Flag = 2.
*/
void * thread2(void * arg)
{
printf("Enter thread2.\n");
printf("this is thread2, g_Flag: %d, thread id is %u.\n",
g_Flag, (unsigned int)pthread_self());

pthread_mutex_lock(&mutex);
if(g_Flag == 1)
pthread_cond_signal(&cond);
g_Flag = 2;
printf("this is thread2, g_Flag: %d, thread id is %u.\n",
g_Flag, (unsigned int)pthread_self());

pthread_mutex_unlock(&mutex);
printf("Leave thread2.\n");
pthread_exit(0);
}

运行结果：

Enter main thread.
Enter thread2.
this is thread2, g_Flag: 0, thread id is 162025472.
Enter thread1.
this is thread1, g_Flag: 0, thread id is 162562048.
this is thread2, g_Flag: 2, thread id is 162025472.
Leave thread2.
this is thread1, g_Flag: 1, thread id is 162562048.
Leave main thread.
LintaodeMBP:MultiThread stjohnson$