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 16384static 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;}