linux-kernel - Re: [PATCH v8 12/19] sched: Introduce task_cpus_dl

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Date:   Thu, 3 Jun 2021 10:52:07 +0100
From:   Will Deacon <will@...nel.org>
To:     Daniel Bristot de Oliveira <bristot@...hat.com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <maz@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Qais Yousef <qais.yousef@....com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Quentin Perret <qperret@...gle.com>, Tejun Heo <tj@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Valentin Schneider <valentin.schneider@....com>,
        kernel-team@...roid.com
Subject: Re: [PATCH v8 12/19] sched: Introduce task_cpus_dl_admissible() to
 check proposed affinity

On Thu, Jun 03, 2021 at 11:43:08AM +0200, Daniel Bristot de Oliveira wrote:
> On 6/2/21 6:47 PM, Will Deacon wrote:
> > In preparation for restricting the affinity of a task during execve()
> > on arm64, introduce a new task_cpus_dl_admissible() helper function to
> > give an indication as to whether the restricted mask is admissible for
> > a deadline task.
> > 
> > Signed-off-by: Will Deacon <will@...nel.org>
> > ---
> >  include/linux/sched.h |  6 ++++++
> >  kernel/sched/core.c   | 44 +++++++++++++++++++++++++++----------------
> >  2 files changed, 34 insertions(+), 16 deletions(-)
> > 
> > diff --git a/include/linux/sched.h b/include/linux/sched.h
> > index 91a6cfeae242..9b17d8cfa6ef 100644
> > --- a/include/linux/sched.h
> > +++ b/include/linux/sched.h
> > @@ -1691,6 +1691,7 @@ extern void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new
> >  extern int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask);
> >  extern int dup_user_cpus_ptr(struct task_struct *dst, struct task_struct *src, int node);
> >  extern void release_user_cpus_ptr(struct task_struct *p);
> > +extern bool task_cpus_dl_admissible(struct task_struct *p, const struct cpumask *mask);
> >  extern void force_compatible_cpus_allowed_ptr(struct task_struct *p);
> >  extern void relax_compatible_cpus_allowed_ptr(struct task_struct *p);
> >  #else
> > @@ -1713,6 +1714,11 @@ static inline void release_user_cpus_ptr(struct task_struct *p)
> >  {
> >  	WARN_ON(p->user_cpus_ptr);
> >  }
> > +
> > +static inline bool task_cpus_dl_admissible(struct task_struct *p, const struct cpumask *mask)
> > +{
> > +	return true;
> > +}
> >  #endif
> >  
> >  extern int yield_to(struct task_struct *p, bool preempt);
> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > index 58e2cf7520c0..b4f8dc18ae11 100644
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -6933,6 +6933,31 @@ SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
> >  	return retval;
> >  }
> >  
> > +#ifdef CONFIG_SMP
> > +bool task_cpus_dl_admissible(struct task_struct *p, const struct cpumask *mask)
> 
> Would you mind renaming it to dl_task_check_affinity(), in the case of a v9? It
> will look coherent with dl_task_can_attach()...

Of course! I struggled with the naming myself, and your suggestion is much
better.

> Reviewed-by: Daniel Bristot de Oliveira <bristot@...hat.com>

Cheers!

Will