linux线程2

线程的属性

• 线程的创建借口pthread_create第二个入参attr指定新建线程的相关属性,一个线程的属性主要包括:线程栈地址和大小,线程的调度策略和优先级,线程是否属于分离detach状态等.
• 属性的初始化和销毁,初始化必须在线程创建接口前

#include <pthread.h>
int pthread_attr_init(pthread_attr_t *attr);  
int pthread_attr_destroy(pthread_attr_t *attr);

• 获取指定线程的属性:

//pthread_getattr_np属于GNU扩展接口,非posix标准,
//#include<pthread.h>前需定义宏_GNU_SOURCE
#define _GNU_SOURCE
#include <pthread.h>
int pthread_getattr_np(pthread_t thread, pthread_attr_t *attr);

• 设置和获取线程的状态
• detachstate参数的取值：
  – PTHREAD_CREATE_JOINABLE，新建线程处于可连接状态，该值为不指定属性创建线程时的默认值。
  – PTHREAD_CREATE_DETACHED，新建线程处于分离状态

#include <pthread.h>
int pthread_attr_setdetachstate(pthread_attr_t *attr, int detachstate);
int pthread_attr_getdetachstate(pthread_attr_t *attr, int *detachstate);

• 设置或获取线程栈地址及大小:

#include <pthread.h>
int pthread_attr_setstack(pthread_attr_t *attr,void *stackaddr, size_t stacksize);
int pthread_attr_getstack(pthread_attr_t *attr, void **stackaddr, size_t *stacksize);

线程attr设置的一个demo代码

//
// Created by wuxiao on 17-5-29.
//
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>

#define handle_error_en(en,msg)\
    errno = en;perror(msg);exit(EXIT_FAILURE);
#define DEFAULT_STACK_SIZE 16384


static void display_pthread_attr(pthread_attr_t *attr,const char* prefix)
{
    int result,state;
    size_t stacksize;
    void* stackaddr;
    struct sched_param sp;

    //获取线程的分离状态
    result = pthread_attr_getdetachstate(attr,&state);
    if(result != 0)
    {
        handle_error_en(result,"pthread_attr_getdetachstate");
    }
    if(state == PTHREAD_CREATE_DETACHED)
    {
        printf("%s Detach state = PTHREAD_CREATE_DETACHED\n",prefix);
    }
    else
    {
        printf("%s Detach state = PTHREAD_CREATE_JOINABLE\n",prefix);
    }

    //获取线程栈地址和栈大小
    result = pthread_attr_getstack(attr,&stackaddr,&stacksize);
    if(result != 0)
    {
        handle_error_en(result,"pthread_attr_getstack");
    }
    printf("%s stack addr = %p\n",prefix,stackaddr);
    printf("%s stack size = 0x%x\n",prefix,(unsigned)stacksize);
}

static void* thread_start(void *arg)
{
    int result;
    pthread_attr_t gattr;
    result = pthread_getattr_np(pthread_self(),&gattr);
    if(result != 0)
    {
        handle_error_en(result,"pthread_getattr_np");
    }

    printf("thread attributes:\n");
    display_pthread_attr(&gattr,"\t");
    exit(EXIT_SUCCESS);
}

int main(int argc,char* argv[])
{
    pthread_t thr;
    pthread_attr_t attr;
    pthread_attr_t *attrp;
    int result;

    attrp = NULL;

    //命令行参数设置线程的栈大小和地址,状态为分离状态

    size_t stack_size = DEFAULT_STACK_SIZE;
    void *sp;
    attrp = &attr;

    result = pthread_attr_init(&attr);
    if(result != 0)
    {
        handle_error_en(result,"pthread_attr_init");
    }

    //设置线程状态
    result = pthread_attr_setdetachstate(&attr,PTHREAD_CREATE_DETACHED);
    if(result != 0)
    {
        handle_error_en(result,"pthread_attr_setdetachstate");
    }

    //获取分配线程栈地址和大小
    if(argc > 1)
    {
        stack_size = strtoul(argv[1], NULL, 0);
    }
    result = posix_memalign(&sp,sysconf(_SC_PAGESIZE),stack_size);
    if(result != 0)
    {
        handle_error_en(result,"posix_memalign");
    }
    printf("posix_memalign() allocated at %p,stacksize = %zu\n",sp,stack_size);

    //更新attr状态的栈大小和地址值
    result = pthread_attr_setstack(&attr,sp,stack_size);
    if(result != 0)
    {
        handle_error_en(result,"pthread_attr_setstack");
    }

    //创建线程
    result = pthread_create(&thr,attrp,&thread_start,NULL);
    if(result != 0)
    {
        handle_error_en(result,"pthread_attr_setstack");
    }
    printf("pthread_create ok,posix_memalign() allocated at %p,stacksize = %zu\n",sp,stack_size);
    //销毁状态
    if(attrp)
    {
        result = pthread_attr_destroy(attrp);
        if(result != 0)
        {
            handle_error_en(result,"pthread_attr_destroy");
        }

    }

    return 0;

}