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Date:   Mon, 18 Jul 2022 23:34:08 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Yury Norov <yury.norov@gmail.com>
Cc:     linux-kernel@vger.kernel.org,
        Alexander Lobakin <alexandr.lobakin@intel.com>,
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Subject: Re: [PATCH 10/16] sched: optimize __set_cpus_allowed_ptr_locked()
Message-ID: <YtXR0D07MwoKN1ii@worktop.programming.kicks-ass.net>
References: <20220718192844.1805158-1-yury.norov@gmail.com>
 <20220718192844.1805158-11-yury.norov@gmail.com>
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On Mon, Jul 18, 2022 at 12:28:38PM -0700, Yury Norov wrote:
> ---
>  kernel/sched/core.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index da0bf6fe9ecd..d6424336ef2d 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2874,7 +2874,8 @@ static int __set_cpus_allowed_ptr_locked(struct task_struct *p,
>  		cpu_valid_mask = cpu_online_mask;
>  	}
>  
> -	if (!kthread && !cpumask_subset(new_mask, cpu_allowed_mask)) {
> +	if (!kthread && new_mask != cpu_allowed_mask &&
> +			!cpumask_subset(new_mask, cpu_allowed_mask)) {

Optimize cpumask_subset() for src1p == src2p instead?

>  		ret = -EINVAL;
>  		goto out;
>  	}
> -- 
> 2.34.1
>