linux-kernel - Re: [tip:sched/core] sched/fair: Use rq_lock/unlock in online_fair_sched

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Message-ID: <20190809172837.GB18727@pauld.bos.csb>
Date:   Fri, 9 Aug 2019 13:28:38 -0400
From:   Phil Auld <pauld@...hat.com>
To:     Dietmar Eggemann <dietmar.eggemann@....com>
Cc:     vincent.guittot@...aro.org, hpa@...or.com,
        linux-kernel@...r.kernel.org, peterz@...radead.org,
        mingo@...hat.com, tglx@...utronix.de, mingo@...nel.org,
        linux-tip-commits@...r.kernel.org
Subject: Re: [tip:sched/core] sched/fair: Use rq_lock/unlock in
 online_fair_sched_group

On Fri, Aug 09, 2019 at 06:21:22PM +0200 Dietmar Eggemann wrote:
> On 8/8/19 1:01 PM, tip-bot for Phil Auld wrote:
> 
> [...]
> 
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 19c58599e967..d9407517dae9 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -10281,18 +10281,18 @@ err:
> >  void online_fair_sched_group(struct task_group *tg)
> >  {
> >  	struct sched_entity *se;
> > +	struct rq_flags rf;
> >  	struct rq *rq;
> >  	int i;
> >  
> >  	for_each_possible_cpu(i) {
> >  		rq = cpu_rq(i);
> >  		se = tg->se[i];
> > -
> > -		raw_spin_lock_irq(&rq->lock);
> > +		rq_lock(rq, &rf);
> >  		update_rq_clock(rq);
> >  		attach_entity_cfs_rq(se);
> >  		sync_throttle(tg, i);
> > -		raw_spin_unlock_irq(&rq->lock);
> > +		rq_unlock(rq, &rf);
> >  	}
> >  }
> 
> Shouldn't this be:
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index d9407517dae9..1054d2cf6aaa 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -10288,11 +10288,11 @@ void online_fair_sched_group(struct task_group
> *tg)
>         for_each_possible_cpu(i) {
>                 rq = cpu_rq(i);
>                 se = tg->se[i];
> -               rq_lock(rq, &rf);
> +               rq_lock_irq(rq, &rf);
>                 update_rq_clock(rq);
>                 attach_entity_cfs_rq(se);
>                 sync_throttle(tg, i);
> -               rq_unlock(rq, &rf);
> +               rq_unlock_irq(rq, &rf);
>         }
>  }
> 
> Currently, you should get a 'inconsistent lock state' warning with
> CONFIG_PROVE_LOCKING.

Yes, indeed. Sorry about that. Maybe it can be fixed in tip before 
it gets any farther?  Or do we need a new patch?


Cheers,
Phil

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