Linux多线程Pthread学习小结

长平狐 发布于 2013/01/06 11:20
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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:

[work@db-testing-com06-vm3.db01.baidu.com pthread]$ gcc -Wall -o pthread_create pthread_create.c -lpthread   

[work@db-testing-com06-vm3.db01.baidu.com 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:

[work@db-testing-com06-vm3.db01.baidu.com pthread]$ gcc -Wall -o pthread_cond2 pthread_cond2.c -lpthread

[work@db-testing-com06-vm3.db01.baidu.com 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key

void 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:

[work@db-testing-com06-vm3.db01.baidu.com pthread]$ gcc -Wall -o pthread_setspecific pthread_setspecific.c -lpthread
[work@db-testing-com06-vm3.db01.baidu.com 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:

 

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

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:

work@db-testing-com06-vm3.db01.baidu.com pthread]$ gcc -Wall -o pthread_once pthread_once.c -lpthread
[work@db-testing-com06-vm3.db01.baidu.com pthread]$ ./pthread_once                                   
hello main
Func: once_run in thread: 1084229984
child_1: thread 1084229984 returns
child_2: thread 1094719840 returns
bye main


原文链接:http://blog.csdn.net/sunboy_2050/article/details/6063067
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