linux-kernel - Re: [PATCH] sched_ext: Avoid multiple irq_work_queue() calls in destroy

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Message-ID: <ab4cd403f47438a1bd1efee45b006b755560e5e6@linux.dev>
Date: Tue, 23 Dec 2025 13:16:46 +0000
From: "Zqiang" <qiang.zhang@...ux.dev>
To: "Andrea Righi" <arighi@...dia.com>
Cc: tj@...nel.org, void@...ifault.com, changwoo@...lia.com,
 sched-ext@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched_ext: Avoid multiple irq_work_queue() calls in
 destroy_dsq()

> 
> 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.

Thank you for make the commit more clear and reviewed :) .

Thanks
Zqiang
 
> 
> > 
> > Signed-off-by: Zqiang <qiang.zhang@...ux.dev>
> > 
> But overall, looks good to me.
> 
> Reviewed-by: Andrea Righi <arighi@...dia.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
> >
>