linux-kernel - Re: [PATCH] sched: core: Remove unnecessary ‘NULL’ values from pending

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Date: Wed, 29 May 2024 11:09:30 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: kunyu <kunyu@...china.com>
Cc: linux-kernel@...r.kernel.org, mingo@...hat.com, juri.lelli@...hat.com,
 peterz@...radead.org, vincent.guittot@...aro.org, dietmar.eggemann@....com,
 rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
 bristot@...hat.com, vschneid@...hat.com
Subject: Re: [PATCH] sched: core: Remove unnecessary ‘NULL’ values from pending

Hello Kunyu,

On 5/28/2024 12:15 PM, kunyu wrote:
> pending is assigned first, so it does not need to initialize the
> assignment.
> 
> Signed-off-by: kunyu <kunyu@...china.com>
> ---
>  kernel/sched/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index bcf2c4cc0522..e32fea8f5830 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2969,7 +2969,7 @@ static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flag
>  	__releases(rq->lock)
>  	__releases(p->pi_lock)
>  {
> -	struct set_affinity_pending my_pending = { }, *pending = NULL;
> +	struct set_affinity_pending my_pending = { }, *pending;

Can "pending" here be initialized to "p->migration_pending" and later
be changed to the updated value of "p->migration_pending" for the
SCA_MIGRATE_ENABLE case?

	if (!(flags & SCA_MIGRATE_ENABLE)) {
		/* serialized by p->pi_lock */
		if (!p->migration_pending) {
			...

			/* Update pending to new value of p->migration_pending */
			pending = p->migration_pending = &my_pending;
		} else {
			...
		}
	}
--

Rest of the initial assignments to "pending" can be dropped then.
Thoughts?

>  	bool stop_pending, complete = false;
>  
>  	/* Can the task run on the task's current CPU? If so, we're done */

--
Thanks and Regards,
Prateek