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SubjectRe: [PATCH 05/16] sched: SCHED_DEADLINE policy implementation.
On 04/23/2012 05:43 PM, Peter Zijlstra wrote:
> On Mon, 2012-04-23 at 17:39 +0200, Juri Lelli wrote:
>> On 04/23/2012 04:35 PM, Peter Zijlstra wrote:
>>> On Fri, 2012-04-06 at 09:14 +0200, Juri Lelli wrote:
>>>> +static void init_dl_task_timer(struct sched_dl_entity *dl_se)
>>>> +{
>>>> + struct hrtimer *timer =&dl_se->dl_timer;
>>>> +
>>>> + if (hrtimer_active(timer)) {
>>>> + hrtimer_try_to_cancel(timer);
>>>> + return;
>>>> + }
>>>
>>> Same question I guess, how can it be active here? Also, just letting it
>>> run doesn't seem like the best way out..
>>>
>>
>> Probably s/hrtimer_try_to_cancel/hrtimer_cancel is better.
>
> Yeah, not sure you can do hrtimer_cancel() there though, you're holding
> ->pi_lock and rq->lock and have IRQs disabled. That sounds like asking
> for trouble.
>
> Anyway, if it can't happen, we don't have to fix it.. so lets answer
> that first ;-)

The user could call __setparam_dl on a throttled task through
__sched_setscheduler.

BTW, I noticed that we should change this (inside __sched_setscheduler):

/*
* If not changing anything there's no need to proceed further
*/
if (unlikely(policy == p->policy && (!rt_policy(policy) ||
param->sched_priority == p->rt_priority))) {

__task_rq_unlock(rq);
raw_spin_unlock_irqrestore(&p->pi_lock, flags);
return 0;
}

to something like this:

if (unlikely(policy == p->policy && (!rt_policy(policy) ||
param->sched_priority == p->rt_priority) &&
!dl_policy(policy)))

Thanks,

- Juri


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