Pthread编程-设置/获取线程属性

Pthread编程-设置/获取线程属性

文章介绍如何设置/获取线程属性。与线程属性相关的函数大都以 pthread_attr_*开头，pthread_attr_get*用于获取线程属性，pthread_attr_get*用于设置线程属性。
这里仅罗列一些比较常用函数：

pthread_attr_init //初始化线程属性变量
pthread_attr_getstackaddr, pthread_attr_setstackaddr //栈地址（已废弃）
pthread_attr_getstacksize, pthread_attr_setstacksize //栈大小
pthread_attr_setguardsize, pthread_attr_getguardsize //保护区大小
pthread_attr_getdetachstate, pthread_attr_setdetachstate //分离属性
pthread_attr_getschedparam, pthread_attr_setschedparam //调度策略变量
pthread_attr_getschedpolicy, pthread_attr_setschedpolicy //调度策略
pthread_attr_getinheritsched, pthread_attr_setinheritsched //继承调度策略
pthread_attr_getscope, pthread_attr_setscope //线程调度竞争范围
pthread_setconcurrency, pthread_getconcurrency //并发级别
pthread_attr_destroy //销毁线程属性变量

其中：

pthread_attr_init()函数初始化线程属性变量为默认值；
pthread_attr_destroy()函数负责销毁线程属性变量
pthread_attr_set*()函数设置对应的线程属性的值
pthread_attr_get*()函数获取对应的线程属性的值

这里只是简单的罗列函数，具体使用可以参考 man function
下面提供一个测试程序：

#include 
#include 
#include 
#include 

#include 
#include 
#include 

#define ERROR(func, ret) {\
    fprintf(stderr, "%s: %s\n", func, strerror(ret)); \
    exit(EXIT_FAILURE); \
}

int main(int argc, char** argv)
{
    pthread_attr_t attr;
    pthread_attr_init(&attr);

    int ret;
    int state;
    ret = pthread_attr_getdetachstate(&attr, &state);
    if(0 != ret) {
        ERROR("pthread_attr_getdetachstate", ret);
    } else {
        if(PTHREAD_CREATE_JOINABLE == state)
            printf("pthread_attr_getdetachstate: PTHREAD_CREATE_JOINABLE\n");
        else if(PTHREAD_CREATE_DETACHED == state)
            printf("pthread_attr_getdetachstate: PTHREAD_CREATE_DETACHED\n");
    }

    void* stackaddr = malloc(PTHREAD_STACK_MIN);
    //printf("stackaddr= %p\n", stackaddr);
    ret = pthread_attr_getstackaddr(&attr, &stackaddr);
    if(0 != ret) {
        ERROR("pthread_attr_getstackaddr", ret);
    } else {
        printf("pthread_attr_getstackaddr: %p\n", stackaddr);
    }
    free(stackaddr);
    stackaddr = NULL;

    size_t size;
    ret = pthread_attr_getstacksize(&attr, &size);
    if(0 != ret) {
        ERROR("pthread_attr_getstacksize", ret);
    } else {
        printf("pthread_attr_getstacksize: %lu\n", size);
    }

    ret = pthread_attr_getguardsize(&attr, &size);
    if(0 != ret) {
        ERROR("pthread_attr_getguardsize", ret);
    } else {
        printf("pthread_attr_getguardsize: %lu\n", size);
    }

    int scope;
    ret = pthread_attr_getscope(&attr, &scope);
    if(0 != ret) {
        ERROR("pthread_attr_getscope", ret);
    } else {
        if(PTHREAD_SCOPE_PROCESS == scope)
            printf("pthread_attr_getscope: PTHREAD_SCOPE_PROCESS\n");
        else if(PTHREAD_SCOPE_SYSTEM == scope)
            printf("pthread_attr_getscope: PTHREAD_SCOPE_SYSTEM\n");
    }

    int policy;
    ret = pthread_attr_getschedpolicy(&attr, &policy);
    if(0 != ret) {
        ERROR("pthread_attr_getchedpolicy", ret);
    } else {
        if(SCHED_FIFO == policy)
            printf("pthread_attr_getschedpolicy: SCHED_FIFO\n");
        else if(SCHED_RR == policy)
            printf("pthread_attr_getschedpolicy: SCHED_RR\n");
        else if(SCHED_OTHER == policy)
            printf("pthread_attr_getschedpolicy: SCHED_OTHER\n");
    }

    int schedinherited;
    ret = pthread_attr_getinheritsched(&attr, &schedinherited);
    if(0 != ret) {
        ERROR("pthread_attr_getinheritsched", ret);
    } else {
        if(PTHREAD_INHERIT_SCHED == schedinherited)
            printf("pthread_attr_getinheritsched: PTHREAD_INHERIT_SCHED\n");
        else if(PTHREAD_EXPLICIT_SCHED == schedinherited)
            printf("pthread_attr_getinheritsched: PTHREAD_EXPLICIT_SCHED\n");
    }

    struct sched_param param; 
    ret = pthread_attr_getschedparam(&attr, ¶m);
    if(0 != ret) {
        ERROR("pthread_attr_getschedparam", ret);
    } else {
            printf("pthread_attr_getschedparam: sched_priority %d\n", 
                                    param.sched_priority);
    }

    pthread_attr_destroy(&attr);

    int level; 
    ret = pthread_getconcurrency();
    if(0 != ret) {
        ERROR("pthread_attr_getconcurrency", ret);
    } else {
            printf("pthread_getconcurrency: level %d\n", level);
    }

    exit(EXIT_SUCCESS);
}

编译运行：

gcc -o proc demo2.c -lpthread

PS: pthread_attr_*函数出错时不会修改全局变量 errno，出错处理时要注意。测试程序只调用 pthread_attr_ get* 函数获取线程的默认属性，pthread_attr_ set*函数调用类似，只不过一般情况下程序使用属性的默认值。