Linux多线程pthread知识总结

简介

POSIX thread 简称为pthread，Posix线程是一个POSIX标准线程.该标准定义内部API创建和操纵线程.

 

作用

线程库实行了POSIX线程标准通常称为pthreads.pthreads是最常用的POSIX系统如Linux和Unix,而微软Windowsimplementations同时存在.举例来说,pthreads-w32可支持MIDP的pthread 　　

Pthreads定义了一套 C程序语言类型、函数与常量，它以 pthread.h 头文件和一个线程库实现。

 

数据类型

pthread_t：线程句柄 　　

pthread_attr_t：线程属性

线程操纵函数（简介起见，省略参数）

pthread_create()：创建一个线程 　　

pthread_exit()：终止当前线程 　　

pthread_cancel()：中断另外一个线程的运行 　　

pthread_join()：阻塞当前的线程，直到另外一个线程运行结束 　　

pthread_attr_init()：初始化线程的属性 　　

pthread_attr_setdetachstate()：设置脱离状态的属性（决定这个线程在终止时是否可以被结合）

pthread_attr_getdetachstate()：获取脱离状态的属性 　　

pthread_attr_destroy()：删除线程的属性 　　

pthread_kill()：向线程发送一个信号

 

同步函数

用于 mutex 和条件变量 　　

pthread_mutex_init() 初始化互斥锁 　　

pthread_mutex_destroy() 删除互斥锁 　　

pthread_mutex_lock()：占有互斥锁（阻塞操作） 　　

pthread_mutex_trylock()：试图占有互斥锁（不阻塞操作）。当互斥锁空闲时将占有该锁；否则立即返回　　

pthread_mutex_unlock(): 释放互斥锁 　　

pthread_cond_init()：初始化条件变量 　　

pthread_cond_destroy()：销毁条件变量 　　

pthread_cond_wait(): 等待条件变量的特殊条件发生

pthread_cond_signal(): 唤醒第一个调用pthread_cond_wait()而进入睡眠的线程 　　 　　

Thread-local storage（或者以Pthreads术语，称作 线程特有数据）: 　　

pthread_key_create(): 分配用于标识进程中线程特定数据的键 　　

pthread_setspecific(): 为指定线程特定数据键设置线程特定绑定 　　

pthread_getspecific(): 获取调用线程的键绑定，并将该绑定存储在 value 指向的位置中 　　

pthread_key_delete(): 销毁现有线程特定数据键

 

与一起工作的工具函数

pthread_equal(): 对两个线程的线程标识号进行比较 　　

pthread_detach(): 分离线程 　　

pthread_self(): 查询线程自身线程标识号

 

详细请参见：

Linux多线程pthread：     http://blog.csdn.net/Sunboy_2050/archive/2010/10/04/5920936.aspx 

Pthread多线程学习小结： http://blog.csdn.net/Sunboy_2050/archive/2010/10/04/5921003.aspx

===================================================================

 

多线程创建

参考代码：

#include<stdio.h>#include<pthread.h>#include<string.h>#include<sys/types.h>#include<unistd.h>pthread_t main_tid;void print_ids(const char *str){    pid_t pid;      //进程id    pthread_t tid;  //线程id    pid = getpid();       //获取当前进程id    tid = pthread_self(); //获取当前线程id    printf("%s pid: %u tid: %u (0x%x)/n",                str,                (unsigned int)pid,                (unsigned int)tid,                (unsigned int)tid);}void *func(void *arg){    print_ids("new  thread:");    return ((void *)0);}int main(){    int err;    err = pthread_create(&main_tid, NULL, func, NULL); //创建线程    if(err != 0){        printf("create thread error: %s/n",strerror(err));        return 1;    }    printf("main thread: pid: %u tid: %u (0x%x)/n",                 (unsigned int)getpid(),                (unsigned int)pthread_self(),                (unsigned int)pthread_self());    print_ids("main thread:");    sleep(1);    return 0;}

运行结果：

[[e-mail] pthread]$ gcc -Wall -o pthread_create pthread_create.c -lpthread   

[[e-mail] pthread]$ ./pthread_create 

main thread: pid: 12531 tid: 2505487232 (0x9556b380)

main thread: pid: 12531 tid: 2505487232 (0x9556b380)

new  thread: pid: 12531 tid: 1084229984 (0x40a00960)

 

===================================================================

 

多线程条件变量

参考代码：

#include <stdio.h>#include <pthread.h>#include <unistd.h>pthread_mutex_t counter_lock;   //互斥锁pthread_cond_t counter_nonzero; //条件变量int counter = 0;int estatus = -1;void *decrement_counter(void *argv);void *increment_counter(void *argv);//******* 主函数 *******//int main(int argc, char **argv){    printf("counter: %d/n", counter);    pthread_t thd1, thd2;    int ret;    //初始化    pthread_mutex_init(&counter_lock, NULL);    pthread_cond_init(&counter_nonzero, NULL);        ret = pthread_create(&thd1, NULL, decrement_counter, NULL); //创建线程1    if(ret){        perror("del:/n");        return 1;    }    ret = pthread_create(&thd2, NULL, increment_counter, NULL); //创建线程2    if(ret){        perror("inc: /n");        return 1;    }    int counter = 0;    while(counter != 10){        printf("counter(main): %d/n", counter); //主线程        sleep(1);        counter++;    }    pthread_exit(0);        return 0;}void *decrement_counter(void *argv){    printf("counter(decrement): %d/n", counter);    pthread_mutex_lock(&counter_lock);    while(counter == 0)        pthread_cond_wait(&counter_nonzero, &counter_lock); //进入阻塞(wait)，等待激活(signal)        printf("counter--(before): %d/n", counter);        counter--; //等待signal激活后再执行    printf("counter--(after): %d/n", counter);        pthread_mutex_unlock(&counter_lock);     return &estatus;}void *increment_counter(void *argv){    printf("counter(increment): %d/n", counter);    pthread_mutex_lock(&counter_lock);    if(counter == 0)        pthread_cond_signal(&counter_nonzero); //激活(signal)阻塞(wait)的线程(先执行完signal线程，然后再执行wait线程)    printf("counter++(before): %d/n", counter);        counter++;     printf("counter++(after): %d/n", counter);        pthread_mutex_unlock(&counter_lock);    return &estatus;}

运行结果：

[[e-mail] pthread]$ gcc -Wall -o pthread_cond2 pthread_cond2.c -lpthread

[[e-mail] pthread]$ ./pthread_cond2 

counter: 0

counter(main): 0

counter(decrement): 0

counter(increment): 0

counter++(before): 0

counter++(after): 1

counter--(before): 1

counter--(after): 0

counter(main): 1

counter(main): 2

counter(main): 3

counter(main): 4

counter(main): 5

counter(main): 6

counter(main): 7

counter(main): 8

counter(main): 9

 

详细解释，请见：http://blog.csdn.net/Sunboy_2050/archive/2010/11/24/6031723.aspx

===================================================================

 

多线程的创建特殊数据键

参考代码：

#include <stdio.h>#include <pthread.h>#include <unistd.h>pthread_key_t key; //声明参数keyvoid echomsg(void *arg) //析构处理函数{    printf("destruct executed in thread = %u, arg = %p/n",                 (unsigned int)pthread_self(),                arg);   }void *child_1(void *arg){    pthread_t tid;       tid = pthread_self();    printf("%s: thread %u enter/n", (char *)arg, (unsigned int)tid);        pthread_setspecific(key, (void *)tid);  // 与key值绑定的value(tid)    printf("%s: thread %u returns %p/n",    // %p 表示输出指针格式                 (char *)arg,                (unsigned int)tid,                 pthread_getspecific(key));  // 获取key值的value    sleep(1);    return NULL;}void *child_2(void *arg){    pthread_t tid;       tid = pthread_self();    printf("%s: thread %u enter/n", (char *)arg, (unsigned int)tid);        pthread_setspecific(key, (void *)tid);    printf("%s: thread %u returns %p/n",                 (char *)arg,                (unsigned int)tid,                 pthread_getspecific(key));    sleep(1);    return NULL;}//******* 主函数 *******//int main(void){    pthread_t tid1, tid2;        printf("hello main/n");        pthread_key_create(&key, echomsg); //创建key        pthread_create(&tid1, NULL, child_1, (void *)"child_1"); //创建带参数的线程，需要强制转换    pthread_create(&tid2, NULL, child_2, (void *)"child_2");    sleep(3);    pthread_key_delete(key); //清除key    printf("bye main/n");        pthread_exit(0);    return 0;}

运行结果：

[[e-mail] pthread]$ gcc -Wall -o pthread_setspecific pthread_setspecific.c -lpthread
[[e-mail] pthread]$ ./pthread_setspecific                                          
hello main
child_1: thread 1084229984 enter
child_1: thread 1084229984 returns 0x40a00960
child_2: thread 1094719840 enter
child_2: thread 1094719840 returns 0x41401960
destruct executed in thread = 1084229984, arg = 0x40a00960
destruct executed in thread = 1094719840, arg = 0x41401960
bye main

 

附加参考——函数原型：

Posix定义了两个API分别用来创建和注销TSD：

int pthread_key_create(pthread_key_t *key, void (*destr_function) (void *))

注销一个TSD采用如下API：

int pthread_key_delete(pthread_key_t key)

int pthread_setspecific(pthread_key_t key, const void *pointer)
void * pthread_getspecific(pthread_key_t key)

参考网址：

http://blog.sina.com.cn/s/blog_46d528490100lxm0.html

http://xunet.blog.51cto.com/138167/22011（推荐）

 

===================================================================

多线程的创建特殊数据键

参考代码：

#include <stdio.h>#include <pthread.h>#include <unistd.h>pthread_once_t once = PTHREAD_ONCE_INIT; //声明变量//once_run()函数仅执行一次，且究竟在哪个线程中执行是不定的//尽管pthread_once(&once,once_run)出现在两个线程中//函数原型：int pthread_once(pthread_once_t *once_control, void (*init_routine)(void))void once_run(void){    printf("Func: %s in thread: %u/n",                 __func__,                 (unsigned int)pthread_self());}void *child_1(void *arg){    pthread_t tid;    tid = pthread_self();    pthread_once(&once, once_run); //调用once_run    printf("%s: thread %d returns/n", (char *)arg, (unsigned int)tid);    return NULL;}void *child_2(void *arg){    pthread_t tid;    tid = pthread_self();    pthread_once(&once, once_run); //调用once_run    printf("%s: thread %d returns/n", (char *)arg, (unsigned int)tid);    return NULL;}//******* main *******//int main(void){    pthread_t tid1, tid2;    printf("hello main/n");    pthread_create(&tid1, NULL, child_1, (void *)"child_1");    pthread_create(&tid2, NULL, child_2, (void *)"child_2");    pthread_join(tid1, NULL);  //main主线程等待线程tid1返回    pthread_join(tid2, NULL);  //main主线程等待线程tid2返回    printf("bye main/n");    return 0;}

运行结果：

[e-mail] pthread]$ gcc -Wall -o pthread_once pthread_once.c -lpthread
[[e-mail] pthread]$ ./pthread_once                                   
hello main
Func: once_run in thread: 1084229984
child_1: thread 1084229984 returns
child_2: thread 1094719840 returns
bye main

参考文献：

          http://blog.csdn.net/sunboy_2050/article/details/6063067

Enjoy it ！