线程属性

线程属性：
attr中包含了以下的多个属性。
初始化与销毁属性：
int pthread_attr_init(pthread_attr_t* attr);
int pthread_attr_destroy(pthread_attr_t* attr);

获取与设置分离属性：
int pthread_attr_getdetachstate(const pthread_attr_t* attr,int* detachstate);
int pthread_attr_setdetachstate(pthread_attr_t* attr,int * detachstate);
PTHREAD_CREATE_DETACHED 或者利用pthread_detach()函数。
PTHREAD_CREATE_JOINABLE//默认不是分离的，需要调用pthread_join函数等待退出。

获取与设置栈的大小：
int pthread_attr_setstacksize(pthread_attr_t* attr,size_t stacksize);
int pthread_attr_getstacksize(pthread_attr_t* attr,size_t* stacksize);

获取或设置线程栈末尾警戒区大小
int pthread_attr_setguardsize(pthread_attr_t *attr, size_t guardsize);
int pthread_attr_getguardsize(const pthread_attr_t *attr, size_t *guardsize);

//获取与设置线程竞争范围
int pthread_attr_setscope(pthread_attr_t *attr, int scope);
int pthread_attr_getscope(const pthread_attr_t *attr, int *scope);
PTHREAD_SCOPE_SYSTEM 进程范围内竞争
PTHREAD_SCOPE_PROCESS 系统范围内竞争

//获取与设置调度策略
int pthread_attr_setschedpolicy(pthread_attr_t *attr, int policy);
int pthread_attr_getschedpolicy(const pthread_attr_t *attr, int *policy);
(相同优先级先进先出调度)SCHED_FIFO, （相同优先级基于抢占式调度,即使优先级相同）SCHED_RR, (默认)SCHED_OTHER

//获取与设置继承调度策略
int pthread_attr_setinheritsched(pthread_attr_t *attr, int inheritsched);
int pthread_attr_getinheritsched(const pthread_attr_t *attr,int *inheritsched);
PTHREAD_INHERIT_SCHED （主线程与新线程相同策略）
PTHREAD_EXPLICIT_SCHED (调度策略属性需要自己设置)

//获取与设置调度参数
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);
struct sched_param {
int sched_priority; // Scheduling priority
};

//获取与设置并发级别。仅在N：M线程模型有效，设置并发级别给内核一个提示：表示提供给定级别数量的核心线程来映射用户线程是高效的。

比如说：用户线程第一级映射成轻量级进程，轻量级进程再一 一映射至核心线程，每个核心线程映射一个CPU。只是提示内核提供多少个轻量级进程是高效的。
int pthread_setconcurrency(int new_level);
int pthread_getconcurrency(void);

#include<unistd.h>
#include<sys/types.h>
#include<fcntl.h>
#include<sys/stat.h>
#include<stdlib.h>
#include<stdio.h>
#include<errno.h>
#include<pthread.h>
#include<string.h>
#define ERR_EXIT(m)
    do
    {
        perror(m);
        exit(EXIT_FAILURE);
    }while(0
int main(void)
{
    pthread_attr_t attr;
    pthread_attr_init(&attr);//attr中有很多  线程属性的默认值
    int state;
    //默认属性是不分离的。要调用pthread_join来防止僵尸
    pthread_attr_getdetachstate(&attr,&state);
    if(state==PTHREAD_CREATE_JOINABLE)
        printf("detachedstate:PTHREAD_CREATE_JOINABLE
");
    else if(state==PTHREAD_CREATE_DETACHED)
        printf("detachedstate:PTHREAD_CREATE_DETACHED
");    //打印线程默认分离属性。
    
    size_t size;
    pthread_attr_getstacksize(&attr,&size);
    printf("stack size:%d
",size);
    //获取警戒缓冲区的大小
    pthread_attr_getguardsize(&attr,&size);
    printf("guardsize:%d
",size);
    
    int scope;
    pthread_attr_getscope(&attr,&scope);
    if(scope==PTHREAD_SCOPE_PROCESS)
        printf("scope:PTHREAD_SCOPE_PROCESS
");
    if(scope==PTHREAD_SCOPE_SYSTEM)
        printf("scope:PTHREAD_SCOPE_SYSTEM
");
    //获取与设置调度策略
    int policy;
    pthread_attr_getschedpolicy(&attr,&policy);
    if(policy==SCHED_FIFO)
        printf("policy:SCHD_FIFO
");
    else if(policy==SCHED_RR)
        printf("policy:SCHED_RR
");
    else if(policy==SCHED_OTHER)
        printf("policy:SCHED_OTHER
");    
    //获取与设置继承调度策略
    int inheritsched;
    pthread_attr_getinheritsched(&attr,&inheritsched);
    if(inheritsched== PTHREAD_INHERIT_SCHED)
        printf("inheritsched: PTHREAD_INHERIT_SCHED
");
    else if(inheritsched==PTHREAD_EXPLICIT_SCHED)
        printf("inheritsched: PTHREAD_EXPLICIT_SCHED");
    //获取与设置调度参数
    struct sched_param param;
    pthread_attr_getschedparam(&attr,&param);
    //调度优先级
    printf("sched_priority:%d
",param.sched_priority);

    pthread_attr_destroy(&attr);
    //并发级别获取
    int level;
    level=pthread_getconcurrency();
    printf("level:%d
",level);
    return 0;

}