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标题:
nice()函数源码有两点疑惑
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作者:
weiweishuo
时间:
2012-10-19 12:27
标题:
nice()函数源码有两点疑惑
看这个源码片段:
---------------------------------------------------------------
void set_user_nice(task_t *p, long nice)
{
unsigned long flags;
prio_array_t *array;
runqueue_t *rq;
int old_prio, new_prio, delta;
1> if (TASK_NICE(p) == nice || nice < -20 || nice > 19)
return;
2> array = p->array;
if (array)
dequeue_task(p, array);
3> old_prio = p->prio;
new_prio = NICE_TO_PRIO(nice);
delta = new_prio - old_prio;
p->static_prio = NICE_TO_PRIO(nice);
p->prio += delta;
4> if (array) {
enqueue_task(p, array);
if (delta < 0 || (delta > 0 && task_running(rq, p)))
resched_task(rq->curr);
}
}
---------------------------------------------------------------
第“3>"处的最后一句“p->prio+=delta”,有两点疑惑:
1,这样一来,一个任务只要调用nice()函数,它的动态优先级立刻被抹去,设置为静态优先级数值。请问是吗?
2,既然p->prio+=delta计算的结果就相当于p->prio=p->static_prio,那为什么不直接写p->prio=p->static_prio,这样意思更明白不是吗?反而p->prio+=delta这句不知所云,难道它有什么特殊含义么?
作者:
weiweishuo
时间:
2012-10-20 13:54
盼高手........
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