線程源碼分析之attr.c（基於linuxthreads2.0.1）

attr.c是線程屬性管理的實現。由於linuxthreads是經過建立一個進程的方式實現線程的，因此屬性中支持設置調度的優先級，調度策略等（參考操做系統的實現）。該文件沒有太多內容。具體做用在分析其餘文件的時候再做分析。

   
     
 
    
    
    
     
     
              
     
 
    

    
      
  
     
     
     
      
      
               
      
  
     
#include <unistd.h>
#include "pthread.h"
#include "internals.h"
// 初始化線程屬性結構體
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;
}
// 設置detach狀態
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;
}
// 設置調度優先級的屬性
int pthread_attr_setschedparam(pthread_attr_t *attr,
 const struct sched_param *param)
{
 // 由系統提供的最大和最小優先級
 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是分時調度，設置成非分時調度須要是超級用戶
 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;
}
// 調度策略來源於繼承仍是顯示設置的
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;
}
// 優先級的有效範圍，PTHREAD_SCOPE_SYSTEM是和系統全部線程競爭，不然是和本進程內的其餘線程競爭
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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