Re: [PATCH 05/16] sched: SCHED_DEADLINE policy implementation.
From: Juri Lelli
Date: Tue May 15 2012 - 06:10:19 EST
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 ;-)
Even if I dropped the bits for allowing !root users, this critical point
still remains.
What if I leave this like it is and instead I do the following?
@@ -488,9 +488,10 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
/*
* We need to take care of a possible races here. In fact, the
* task might have changed its scheduling policy to something
- * different from SCHED_DEADLINE (through sched_setscheduler()).
+ * different from SCHED_DEADLINE or changed its reservation
+ * parameters (through sched_{setscheduler(),setscheduler2()}).
*/
- if (!dl_task(p))
+ if (!dl_task(p) || dl_se->dl_new)
goto unlock;
dl_se->dl_throttled = 0;
The idea is that hrtimer_try_to_cancel should fail only if the callback routine
is running. If, meanwhile, I set up new parameters, I can try to recognize this
situation through dl_new (set to 1 during __setparam_dl).
BTW, I'd have a new version ready (also rebased on the current tip/master). It
address all the comments excluding your gcc work-around, math128 and
nr_cpus_allowed shift (patches are ready but those changes not yet mainline,
right?). Anyway, do you think would be fine to post it?
Thanks and Regards,
- Juri
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