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thread 線程屬性脫離線程

線程的屬性

脫離線程:不向主線程返回信息,不需要主線程等待.
通過兩種方法創建:
調用pthread_detach;
修改線程的屬性. <- 這里使用

#include <pthread.h>
int pthread_attr_init(pthread_attr_t *attr);
初始化一個線程屬性對象.
pthread_destroy
回收一個線程屬性對象.

#include <pthread.h>
int pthread_attr_setdetachstate(pthread_attr_t *attr, int detachstate);
int pthread_attr_getdetachstate(const pthread_attr_t *attr, int *detachstate);
這個屬性允許我們無需對線程進行合并:
| PTHREAD_CREATE_JOINABLE 默認.
| PTHREAD_CREATE_DETACHED 不能調用pthread_join來獲得另一個線程的退出狀態.

int pthread_attr_setschedpolicy(pthread_attr_t *attr, int policy);
int pthread_attr_getschedpolicy(const pthread_attr_t *attr, int *policy);
控制線程的調度方式:
| SCHED_OTHER 默認
| SCHED_RP 循環(round_robin) <- 下面2個調度方式具備實時調度功能,需要root權限.
| SCHED_FIFO 先進先出

int pthread_attr_setschedparam(pthread_attr_t *attr, const struct sched_param *param);
int pthread_attr_getschedparam(const pthread_attr_t *attr, struct sched_param *param);
和schedpolicy配合使用,控制SCHED_OTHER線程的調度策略.

int pthread_attr_setinheritsched(pthread_attr_t *attr, int inherit);
int pthread_attr_getinheritsched(const pthread_attr_t *attr, int *inherit);
| PTHREAD_EXPLICIT_SCHED 調度由屬性明確設置.
| PTHREAD_INHERIT_SCHED 新線程沿用創建者的屬性.

int pthread_attr_setscope(pthread_attr_t *attr, int scope);
int pthread_attr_getscope(const pthread_attr_t *attr, int *scope);
控制一個線程調度的計算方式,目前Linux只支持PTHREAD_SCOPE_SYSTEM.

int pthread_attr_setstacksize(pthread_attr_t *attr, int scope);
int pthread_attr_getstacksize(const pthread_attr_t *attr, int *scope);
控制線程創建的棧大小,單位字節.可選.
Linux在實現線程時,默認的棧很大,這個屬性有點多余.

創建脫離線程:

/*
* 線程屬性-創建脫離線程
* 主線程不等待子線程結束,只通過thread_finished標志來檢測子線程是否已結束,并顯示線程之間仍然共享的變量.
*/
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <pthread.h>

void *thread_function(void *arg);

char g_message[] = "Hello World!";
int g_thread_finished = 0;

int main(){
    int res;
    pthread_t a_thread;
    pthread_attr_t thread_attr;

    res = pthread_attr_init(&thread_attr);
    if(res != 0){
        perror("Attribute creation failed");
        exit(EXIT_FAILURE);
    }

    res = pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_DETACHED);
    if(res != 0){
        perror("Setting detached attribute failed");
        exit(EXIT_FAILURE);
    }

    res = pthread_create(&a_thread, &thread_attr,
            thread_function, (void *)g_message);
    if(res != 0){
        perror("Thread creation failed");
        exit(EXIT_FAILURE);
    }

    (void)pthread_attr_destroy(&thread_attr);
    while(!g_thread_finished){
        printf("Waiting for thread to say it's finished

\n");
        sleep(1);
    }
    printf("Other thread finished, bye!\n");
    exit(EXIT_SUCCESS);
}

void *thread_function(void *arg){
    printf("thread_function is running. Argument was %s\n", (char *)arg);
    sleep(4);
    printf("Second thread setting finished flag, and exit now\n");
    g_thread_finished = 1;
    pthread_exit(NULL);
}

執行結果:

$ gcc -D_REENTRANT thread5.c -o thread5 -lpthread
$ ./thread5
Waiting for thread to say it's finished

thread_function is running. Argument was Hello World!
Waiting for thread to say it's finished

Waiting for thread to say it's finished

Second thread setting finished flag, and exit now
Other thread finished, bye!

--
FROM: Linux程序設計

posted on 2011-06-14 18:56 小默閱讀(2229) 評論(0) 編輯收藏引用所屬分類: Linux

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thread 線程屬性脫離線程