多執行緒脫離狀態 + 排程

pthread_join 用來等待執行緒結束
不希望等待執行緒結束 就是用脫離狀態(備註：程式結束了執行緒依然會結束)
根據文件 join 和 detached 要設定其中一種 否則多執行緒容易造成記憶體洩漏

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<pthread.h>

void *thread_function(void *arg);
char message[] = "Hello World";
int thread_exited = 0;

int main(){
    int res;
    pthread_t a_thread;
    void *thread_result;
    pthread_attr_t thread_attr;

    //不設定此屬性也可以正常執行
    //根據文件 join 和 detached 要設定其中一種 否則多執行緒容易造成記憶體洩漏
    pthread_attr_init(&thread_attr);
    pthread_attr_setdetachstate(&thread_attr,PTHREAD_CREATE_DETACHED);



    //設定排程屬性
    int max_priority;
    int min_priority;
    struct sched_param scheduling_value;

    //排程範圍
    max_priority = sched_get_priority_max(SCHED_OTHER);
    min_priority = sched_get_priority_min(SCHED_OTHER);

    scheduling_value.sched_priority = min_priority;
    pthread_attr_setschedparam(&thread_attr,&scheduling_value); 

    res = pthread_create(&a_thread,&thread_attr,thread_function,(void *)message);
    if(res != 0){ 
        perror("Thread creation failed");
        exit(EXIT_FAILURE);
    }   
    printf("Waiting for thread to finish...\n");
    //res = pthread_join(a_thread,&thread_result);
    //printf("Thread joined,it returned %s\n",(char *)thread_result);
    while(!thread_exited){
        printf("I'm waiting...\n");
        sleep(1);
    }   
    printf("Message is now %s\n",message);
    exit(EXIT_SUCCESS);
}
void *thread_function(void *arg){
    printf("thread_function is running, Argument was %s\n",(char *)arg);
    sleep(3);
    strcpy(message,"Bye!");

    thread_exited = 1;
    pthread_exit("Thank you ro the CPU time");
}