Messages in this thread | | | Date | Fri, 21 Apr 2017 21:08:33 +0200 | From | luca abeni <> | Subject | Re: [PATCH] sched/deadline: fix switching to -deadline |
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On Fri, 21 Apr 2017 11:26:59 +0100 Juri Lelli <juri.lelli@arm.com> wrote: > On 21/04/17 11:59, Luca Abeni wrote: > > On Fri, 21 Apr 2017 10:47:29 +0100 > > Juri Lelli <juri.lelli@arm.com> wrote: > > [...] > > > > > > *dl_se, update_dl_entity(dl_se, pi_se); > > > > > > else if (flags & ENQUEUE_REPLENISH) > > > > > > replenish_dl_entity(dl_se, pi_se); > > > > > > + else if ((flags & ENQUEUE_RESTORE) && > > > > > > > > > > Not sure I understand how this works. AFAICT we are doing > > > > > __sched_setscheduler() when we want to catch the case of a new > > > > > dl_entity (SCHED_{OTHER,FIFO} -> SCHED_DEADLINE}, but > > > > > queue_flags (which are passed to enqueue_task()) don't seem > > > > > to have ENQUEUE_RESTORE set? > > > > > > > > I was under the impression sched_setscheduler() sets > > > > ENQUEUE_RESTORE... > > > > > > Oh, I think it works "by coincidence", as ENQUEUE_RESTORE == > > > DEQUEUE_SAVE == 0x02 ? :) > > > > Not sure if this is a conincidence... By looking at the comments in > > sched/sched.h I got the impression the two values match by design > > (and __sched_setscheduler() is using this property to simplify the > > code :) > > Yep, right. > > Do you think we might get into trouble with do_set_cpus_allowed()? > Can it happen that we change a task affinity while its deadline is in > the past?
Well, double thinking about it, this is an interesting problem... What do we want to do with do_set_cpus_allowed()? (I mean: what is the expected behaviour?)
With this patch, if a task is moved to a different runqueue when its deadline is in the past (because we are doing gEDF, or because of timer granularity issues) its scheduling deadline is reinitialized to current time + relative deadline... I think this makes perfect sense, doesn't it?
Luca
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