linux pthread线程学习

#include <pthread.h>//新建线程int pthread_create(pthread_t *restrict tidp, const pthread_attr_t *restrict attr, void *(*start_rtn)(void *), void *restrict arg);//线程终止void pthread_exit(void *rval_ptr);//线程自身主动退出int pthread_join(pthread_t tid, void **rval_ptr);//其他线程阻塞自身，等待tid退出//线程清理void pthread_cleanup_push(void (*rtn)(void *), void *arg);void pthread_cleanup_pop(int execute);

补充说明：

1. 线程创建

pthread_create()函数返回值0，表示创建成功，线程id保存载tidp中；失败则返回非零，需自行处理，不会修改errno值

2. 线程终止

a. 任一线程调用exit, _Exit, _exit都将导致整个进程终止；

b. 单个线程退出方式有三种：

　　1> 线程执行函数start_rtn()中使用return返回，返回值为线程退出码；

　　2> 被同一个进程的其他线程使用pthread_cancel()取消；

　　3> 线程自身调用了pthread_exit()；

说明：pthread_join(pthread_t tid, void **rval_ptr)函数会阻塞调用线程，直到tid线程通过上述三种方式终止退出，且return/pthread_exit()方式会设置相应线程退出码rval_ptr，而pthread_cancel()取消的线程，将退出码设置为PTHREAD_CANCELED.

3. 线程清理处理程序（thread cleanup handler）

3.a> pthread_cleanup_push()与pthread_cleanup_pop()均为<pthread.h>中实现的宏定义，具体实现如下：

pthread_cleanup_push and pthread_cleanup_pop are macros and must always   be used in matching pairs at the same nesting level of braces.  */#  define pthread_cleanup_push(routine, arg) \  do {      \    __pthread_cleanup_class __clframe (routine, arg)/* Remove a cleanup handler installed by the matching pthread_cleanup_push.   If EXECUTE is non-zero, the handler function is called. */#  define pthread_cleanup_pop(execute) \    __clframe.__setdoit (execute);      \  } while (0)

 可见push/pop中的{/}是一一对应的，因此pthread_cleanup_push/pop()也应一一对应出现，否则编译出错。

3.b> 当线程执行下列之一操作时调用清理函数，thread_cleanup_push由栈结构实现，注意清理程序调用的顺序，先入后出。

　　1: 调用pthread_exit()时，而直接return不会出发清理函数；

　　2: 相应取消请求pthread_cancel()时；

　　3: 使用非零execute参数调用pthread_cleanup_pop()时；

尤其需注意pthread_cleanup_pop()参数不同及此语句所处位置不同而有不同效果。

看此代码实例，注意return或pthread_exit()位置不同导致pthread_cleanup_pop()不同参数的效果变化。

#include <pthread.h>void testPointerSize(){void *tret;printf("size of pointer in x86-64：%d\n",sizeof(tret));//result is 8 in x86-64.//which is 4 in x86-32.printf("size of int in x86-64：%d\n",sizeof(int));//result is 4 in x86-64.//which is also 4 in x86-32.}void cleanup(void *arg){printf("cleanup:%s\n",(char *)arg);}void * thr_fn1(void *arg){printf("thread 1 start\n");pthread_cleanup_push(cleanup, "thread 1 first handler");pthread_cleanup_push(cleanup, "thread 1 second handler");if(arg)return ((void *)1);//arg !=0 ,return here.//return here will not triger any cleanup.pthread_cleanup_pop(0);pthread_cleanup_pop(1);return ((void *)2);//will not run this}void * thr_fn2(void *arg){printf("thread 2 start\n");pthread_cleanup_push(cleanup, "thread 2 first handler");pthread_cleanup_push(cleanup, "thread 2 second handler");pthread_cleanup_pop(0);pthread_cleanup_pop(1);return ((void *)2);//return here can triger cleanup second handler;}void * thr_fn3(void *arg){printf("thread 3 start\n");pthread_cleanup_push(cleanup, "thread 3 first handler");pthread_cleanup_push(cleanup, "thread 3 second handler");if(arg)pthread_exit((void *)3);//pthread_exit() here will triger both cleanup first&second handler.pthread_cleanup_pop(1);pthread_cleanup_pop(0);pthread_exit((void *)3);//wont run this}void * thr_fn4(void *arg){printf("thread 4 start\n");pthread_cleanup_push(cleanup, "thread 4 first handler");pthread_cleanup_push(cleanup, "thread 4 second handler");pthread_cleanup_pop(1);pthread_cleanup_pop(0);pthread_exit((void *)4);//pthread_exit() here will triger cleanup second handler.}int main(void){testPointerSize();int err;pthread_t tid1, tid2, tid3, tid4;void *tret;err = pthread_create(&tid1, NULL, thr_fn1, (void *)1);err = pthread_join(tid1,&tret);printf("thread 1 exit code %d\n",(int)tret);err = pthread_create(&tid2, NULL, thr_fn2, (void *)2);err = pthread_join(tid2, &tret);printf("thread 2 exit code %d\n",(int)tret);err = pthread_create(&tid3, NULL, thr_fn3, (void *)3);err = pthread_join(tid3,&tret);printf("thread 3 exit code %d\n",(int)tret);err = pthread_create(&tid4, NULL, thr_fn4, (void *)4);err = pthread_join(tid4, &tret);printf("thread 4 exit code %d\n",(int)tret);}

 运行结果：

[root@hello testData]# ./test size of pointer in x86-64：8size of int in x86-64：4thread 1 startthread 1 exit code 1thread 2 startcleanup:thread 2 first handlerthread 2 exit code 2thread 3 startcleanup:thread 3 second handlercleanup:thread 3 first handlerthread 3 exit code 3thread 4 startcleanup:thread 4 second handlerthread 4 exit code 4

  由上述测试程序总结如下：

1> push与pop间的return，将导致清理程序不被触发；

2> 位于pop之后return，由pop的参数确定是否触发清理程序，非零参数触发，零参数不触发；

3> push/pop间的pthread_exit()，将触发所有清理函数；

4>位于pop之后的pthread_exit()时，pop参数决定是否触发清理程序；

其实，上述四种情况只是测试验证了前文3.b所说三个条件，加深理解。