Linux多线程Pthread学习小结
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：
[[email protected] pthread]$ gcc -Wall -o pthread_create pthread_create.c -lpthread
[[email protected] 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：
[[email protected] pthread]$ gcc -Wall -o pthread_cond2 pthread_cond2.c -lpthread
[[email protected] 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：
[[email protected] pthread]$ gcc -Wall -o pthread_setspecific pthread_setspecific.c -lpthread
[[email protected] 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：
void * pthread_getspecific(pthread_key_t key)
===================================================================
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：
[email protected] pthread]$ gcc -Wall -o pthread_once pthread_once.c -lpthread
[[email protected] pthread]$ ./pthread_once
hello main
Func: once_run in thread: 1084229984
child_1: thread 1084229984 returns
child_2: thread 1094719840 returns
bye main