Re: [PATCH v33 2/7] sched/core: Use the scheduling context for remote ticks

[Kayra Cizmeci]

On Fri, Oct 23, 2026 at 10:04:13PM +0000, John Stultz wrote:
> From: "Shubhang Kaushik (Ampere)" <sh@xxxxxxxxxx>

Hi John and Shubhang,

> ---
>  kernel/sched/core.c | 14 ++++----------
>  1 file changed, 4 insertions(+), 10 deletions(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 0ab15f03cb947..729ebaca35e1a 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -5934,26 +5934,20 @@ static void sched_tick_remote(struct work_struct *work)
>  	 */
>  	if (tick_nohz_tick_stopped_cpu(cpu)) {
>  		guard(rq_lock_irq)(rq);
> -		struct task_struct *curr = rq->curr;
> +		struct task_struct *donor = rq->donor;
>  
>  		if (cpu_online(cpu)) {
> -			/*
> -			 * Since this is a remote tick for full dynticks mode,
> -			 * we are always sure that there is no proxy (only a
> -			 * single task is running).
> -			 */
> -			WARN_ON_ONCE(rq->curr != rq->donor);
>  			update_rq_clock(rq);
>  
> -			if (!is_idle_task(curr)) {
> +			if (!is_idle_task(donor)) {
>  				/*
>  				 * Make sure the next tick runs within a
>  				 * reasonable amount of time.
>  				 */
> -				u64 delta = rq_clock_task(rq) - curr->se.exec_start;
> +				u64 delta = rq_clock_task(rq) - donor->se.exec_start;
>  				WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 30);
>  			}
> -			curr->sched_class->task_tick(rq, curr, 0);
> +			donor->sched_class->task_tick(rq, donor, 0);
>  
>  			calc_load_nohz_remote(rq);
>  		}


The old code already assumes that donor always being equal to
curr. If this is not true, patch is needed. If this true, patch
doesn't change anything since curr == donor. :-).

So even if it's true, this doesn't messes with anything.

And IMO, using donor instead of curr is already cleaner than using
curr. Since we don't need this WARN_ON_ONCE and the comment. AFAICT
more robust too.

So...

(Dramatical pause, important for scenery.)

Reviewed-by: Kayra Cizmeci <kayracizmeci@xxxxxxxxx>

Thanks!


Kayra