Re: [PATCH 1/3] sched/deadline: clear dl_entity params when setscheduling to different class

[Wanpeng Li]

ping,

ä 10/8/14, 8:32 PM, Wanpeng Li åé:
> Hi Juri,
>
> ä 9/19/14, 5:22 PM, Juri Lelli åé:
> > When a task is using SCHED_DEADLINE and the user setschedules it to a 
> > different
> > class its sched_dl_entity static parameters are not cleaned up. This 
> > causes a
> > bug if the user sets it back to SCHED_DEADLINE with the same 
> > parameters again.
> > The problem resides in the check we perform at the very beginning of
> > dl_overflow():
> >
> >     if (new_bw == p->dl.dl_bw)
> >         return 0;
> >
> > This condition is met in the case depicted above, so the function 
> > returns and
> > dl_b->total_bw is not updated (the p->dl.dl_bw is not added to it). 
> > After this,
>
> As you know there is no static parameter clear before this patch, so 
> if p->dl.dl_bw will decrease from dl_b->total_bw when the user 
> setschedules to a different class instead of dl?
>
> Regards,
> Wanpeng Li
>
> > admission control is broken.
> >
> > This patch fixes the thing, properly clearing static parameters for a 
> > task
> > that ceases to use SCHED_DEADLINE.
> >
> > Reported-by: Daniele Alessandrelli <daniele.alessandrelli@xxxxxxxxx>
> > Reported-by: Daniel Wagner <daniel.wagner@xxxxxxxxxxxx>
> > Reported-by: Vincent Legout <vincent@xxxxxxxxxxx>
> > Tested-by: Luca Abeni <luca.abeni@xxxxxxxx>
> > Signed-off-by: Juri Lelli <juri.lelli@xxxxxxx>
> > Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> > Cc: Juri Lelli <juri.lelli@xxxxxxxxx>
> > Cc: Dario Faggioli <raistlin@xxxxxxxx>
> > Cc: Michael Trimarchi <michael@xxxxxxxxxxxxxxxxxxxx>
> > Cc: Fabio Checconi <fchecconi@xxxxxxxxx>
> > Cc: linux-kernel@xxxxxxxxxxxxxxx
> > ---
> >   kernel/sched/core.c     | 19 +++++++++++++++----
> >   kernel/sched/deadline.c |  2 ++
> >   kernel/sched/sched.h    |  3 +++
> >   3 files changed, 20 insertions(+), 4 deletions(-)
> >
> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > index ec1a286..581a429 100644
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -1776,6 +1776,20 @@ int wake_up_state(struct task_struct *p, 
> > unsigned int state)
> >   }
> >     /*
> > + * This function clears the sched_dl_entity static params.
> > + */
> > +void __dl_clear_params(struct task_struct *p)
> > +{
> > +    struct sched_dl_entity *dl_se = &p->dl;
> > +
> > +    dl_se->dl_runtime = 0;
> > +    dl_se->dl_deadline = 0;
> > +    dl_se->dl_period = 0;
> > +    dl_se->flags = 0;
> > +    dl_se->dl_bw = 0;
> > +}
> > +
> > +/*
> >    * Perform scheduler related setup for a newly forked process p.
> >    * p is forked by current.
> >    *
> > @@ -1799,10 +1813,7 @@ static void __sched_fork(unsigned long 
> > clone_flags, struct task_struct *p)
> >         RB_CLEAR_NODE(&p->dl.rb_node);
> >       hrtimer_init(&p->dl.dl_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
> > -    p->dl.dl_runtime = p->dl.runtime = 0;
> > -    p->dl.dl_deadline = p->dl.deadline = 0;
> > -    p->dl.dl_period = 0;
> > -    p->dl.flags = 0;
> > +    __dl_clear_params(p);
> >         INIT_LIST_HEAD(&p->rt.run_list);
> >   diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> > index 255ce13..4a51b14 100644
> > --- a/kernel/sched/deadline.c
> > +++ b/kernel/sched/deadline.c
> > @@ -1569,6 +1569,8 @@ static void switched_from_dl(struct rq *rq, 
> > struct task_struct *p)
> >       if (hrtimer_active(&p->dl.dl_timer) && !dl_policy(p->policy))
> >           hrtimer_try_to_cancel(&p->dl.dl_timer);
> >   +    __dl_clear_params(p);
> > +
> >   #ifdef CONFIG_SMP
> >       /*
> >        * Since this might be the only -deadline task on the rq,
> > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> > index 579712f..4890484 100644
> > --- a/kernel/sched/sched.h
> > +++ b/kernel/sched/sched.h
> > @@ -126,6 +126,9 @@ struct rt_bandwidth {
> >       u64            rt_runtime;
> >       struct hrtimer        rt_period_timer;
> >   };
> > +
> > +void __dl_clear_params(struct task_struct *p);
> > +
> >   /*
> >    * To keep the bandwidth of -deadline tasks and groups under control
> >    * we need some place where:

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