线程源码分析之attr.c（基于linuxthreads2.0.1）

attr.c是线程属性管理的实现。由于linuxthreads是经过建立一个进程的方式实现线程的，因此属性中支持设置调度的优先级，调度策略等（参考操做系统的实现）。该文件没有太多内容。具体做用在分析其余文件的时候再做分析。

   
     
 
    
    
    
     
     
              
     
 
    

    
      
  
     
     
     
      
      
               
      
  
     
#include <unistd.h>
#include "pthread.h"
#include "internals.h"
// 初始化线程属性结构体
int pthread_attr_init(pthread_attr_t *attr)
{
 attr->detachstate = PTHREAD_CREATE_JOINABLE;
 attr->schedpolicy = SCHED_OTHER;
 attr->schedparam.sched_priority = 0;
 attr->inheritsched = PTHREAD_EXPLICIT_SCHED;
 attr->scope = PTHREAD_SCOPE_SYSTEM;
 return 0;
}

int pthread_attr_destroy(pthread_attr_t *attr)
{
 return 0;
}
// 设置detach状态
int pthread_attr_setdetachstate(pthread_attr_t *attr, int detachstate)
{
 if (detachstate < PTHREAD_CREATE_JOINABLE ||
 detachstate > PTHREAD_CREATE_DETACHED)
 return EINVAL;
 attr->detachstate = detachstate;
 return 0;
}

int pthread_attr_getdetachstate(const pthread_attr_t *attr, int *detachstate)
{
 *detachstate = attr->detachstate;
 return 0;
}
// 设置调度优先级的属性
int pthread_attr_setschedparam(pthread_attr_t *attr,
 const struct sched_param *param)
{
 // 由系统提供的最大和最小优先级
 int max_prio = sched_get_priority_max(attr->schedpolicy);
 int min_prio = sched_get_priority_min(attr->schedpolicy);

 if (param->sched_priority < min_prio || param->sched_priority > max_prio)
 return EINVAL;
 attr->schedparam = *param;
 return 0;
}

int pthread_attr_getschedparam(const pthread_attr_t *attr,
 struct sched_param *param)
{
 *param = attr->schedparam;
 return 0;
}

int pthread_attr_setschedpolicy(pthread_attr_t *attr, int policy)
{
 if (policy != SCHED_OTHER && policy != SCHED_FIFO && policy != SCHED_RR)
 return EINVAL;
 // SCHED_OTHER是分时调度，设置成非分时调度须要是超级用户
 if (policy != SCHED_OTHER && geteuid() != 0)
 return ENOTSUP;
 attr->schedpolicy = policy;
 return 0;
}

int pthread_attr_getschedpolicy(const pthread_attr_t *attr, int *policy)
{
 *policy = attr->schedpolicy;
 return 0;
}
// 调度策略来源于继承仍是显示设置的
int pthread_attr_setinheritsched(pthread_attr_t *attr, int inherit)
{
 if (inherit != PTHREAD_INHERIT_SCHED && inherit != PTHREAD_EXPLICIT_SCHED)
 return EINVAL;
 attr->inheritsched = inherit;
 return 0;
}

int pthread_attr_getinheritsched(const pthread_attr_t *attr, int *inherit)
{
 *inherit = attr->inheritsched;
 return 0;
}
// 优先级的有效范围，PTHREAD_SCOPE_SYSTEM是和系统全部线程竞争，不然是和本进程内的其余线程竞争
int pthread_attr_setscope(pthread_attr_t *attr, int scope)
{
 switch (scope) {
 case PTHREAD_SCOPE_SYSTEM:
 attr->scope = scope;
 return 0;
 case PTHREAD_SCOPE_PROCESS:
 return ENOTSUP;
 default:
 return EINVAL;
 }
}

int pthread_attr_getscope(const pthread_attr_t *attr, int *scope)
{
 *scope = attr->scope;
 return 0;
}
   
     
 
    
    
    
     
     
              
     
 
    
   
     
 
    
    
    
     
     
              
     
 
    

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