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Subject[Question]How to restrict some kind of task?
Hi, All.

I want to restrict some kind of task.

For example, for some task have one schedule policy SCHED_XYZ, when
it reach beyond
40% CPU time, we force it yield CPU.

I inserted some code in scheduler_tick(), like this:

> if (check_task_overload(rq)) {
> if (xyz_task(p) && yield_cpu(p, rq)) {
> set_tsk_need_resched(p);
> p->prio = effective_prio(p);
> p->time_slice = task_timeslice(p);
> p->first_time_slice = 0;
> goto out_unlock;
> }
> }


Of course, before these code, we hold our rq->lock first, so we should
go to 'out_unlock'.
The function xyz_task(p) just is macro (p->policy == SCHED_XYZ), and
yield_cpu() also is simple, it just move the task to expired array,

int yield_cpu(task_t *p, runqueue_t *rq)
{
dequeue_task(p, p->array);
requeue_task(p, rq->expired);
return 1;
}
These code are so simple, but is make system crash, if I create some
XYZ policy task.

I tried the more radical idea (remove these tasks from runqueue to
our one
list_head that spin_lock protected), but crash again and again.

if need, I can paste my global patch.

Thanks in advanced.

-liyu





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