Re: [PATCH] sched_ext: Avoid multiple irq_work_queue() calls in destroy_dsq()

[Andrea Righi <arighi@nvidia.com>]

On Mon, Dec 22, 2025 at 07:53:18PM +0800, Zqiang wrote:
> This commit only make irq_work_queue() to be called when the
> llist_add() returns true.

Just to be more clear, we could rephrase the commit message as follows:

llist_add() returns true only when adding to an empty list, which indicates
that no IRQ work is currently queued or running. Therefore, we only need to
call irq_work_queue() when llist_add() returns true, to avoid unnecessarily
re-queueing IRQ work that is already pending or executing.

> 
> Signed-off-by: Zqiang <qiang.zhang@linux.dev>

But overall, looks good to me.

Reviewed-by: Andrea Righi <arighi@nvidia.com>

Thanks,
-Andrea

> ---
>  kernel/sched/ext.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
> index 8f6d8d7f895c..136b01950a62 100644
> --- a/kernel/sched/ext.c
> +++ b/kernel/sched/ext.c
> @@ -3439,8 +3439,8 @@ static void destroy_dsq(struct scx_sched *sch, u64 dsq_id)
>  	 * operations inside scheduler locks.
>  	 */
>  	dsq->id = SCX_DSQ_INVALID;
> -	llist_add(&dsq->free_node, &dsqs_to_free);
> -	irq_work_queue(&free_dsq_irq_work);
> +	if (llist_add(&dsq->free_node, &dsqs_to_free))
> +		irq_work_queue(&free_dsq_irq_work);
>  
>  out_unlock_dsq:
>  	raw_spin_unlock_irqrestore(&dsq->lock, flags);
> -- 
> 2.17.1
>