linux-kernel - Re: [PATCH 2/5] irq_work: Ensure that irq

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Message-ID: <20211005154827.h2pna3vfqbo7icjn@linutronix.de>
Date:   Tue, 5 Oct 2021 17:48:27 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     linux-kernel@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 2/5] irq_work: Ensure that irq_work runs in in-IRQ
 context.

On 2021-09-27 23:19:16 [+0200], To linux-kernel@...r.kernel.org wrote:
> The irq-work callback should be invoked in hardirq context and some
> callbacks rely on this behaviour. At the time irq_work_run_list()
> interrupts should be disabled but the important part is that the
> callback is invoked from a in-IRQ context.
> The "disabled interrupts" check can be satisfied by disabling interrupts
> from a kworker which is not the intended context.
> 
> Ensure that the callback is invoked from hardirq context and not just
> with disabled interrupts.

As noted by lkp, this triggers from smpcfd_dying_cpu().
Do we care enough to change this or should I rather drop this one?

> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> ---
>  kernel/irq_work.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/irq_work.c b/kernel/irq_work.c
> index db8c248ebc8c8..caf2edffa20d5 100644
> --- a/kernel/irq_work.c
> +++ b/kernel/irq_work.c
> @@ -167,7 +167,7 @@ static void irq_work_run_list(struct llist_head *list)
>  	struct irq_work *work, *tmp;
>  	struct llist_node *llnode;
>  
> -	BUG_ON(!irqs_disabled());
> +	BUG_ON(!in_hardirq());
>  
>  	if (llist_empty(list))
>  		return;

Sebastian