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Subject: Re: [PATCH v8 12/19] sched: Introduce task_cpus_dl_admissible() to
 check proposed affinity
To:     Will Deacon <will@kernel.org>, linux-arm-kernel@lists.infradead.org
Cc:     linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
        Catalin Marinas <catalin.marinas@arm.com>,
        Marc Zyngier <maz@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Morten Rasmussen <morten.rasmussen@arm.com>,
        Qais Yousef <qais.yousef@arm.com>,
        Suren Baghdasaryan <surenb@google.com>,
        Quentin Perret <qperret@google.com>, Tejun Heo <tj@kernel.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Ingo Molnar <mingo@redhat.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Valentin Schneider <valentin.schneider@arm.com>,
        kernel-team@android.com
References: <20210602164719.31777-1-will@kernel.org>
 <20210602164719.31777-13-will@kernel.org>
From:   Daniel Bristot de Oliveira <bristot@redhat.com>
Message-ID: <5ab65165-49e6-633f-d4a5-9538fb72cc36@redhat.com>
Date:   Thu, 3 Jun 2021 11:43:08 +0200
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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@kernel.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()...

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

Thanks!
-- Daniel