linux-kernel - Re: [PATCH 04/15] irq: simplify handle_domain

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Date:   Fri, 22 Oct 2021 11:52:28 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     linux-kernel@...r.kernel.org, aou@...s.berkeley.edu,
        catalin.marinas@....com, deanbo422@...il.com, green.hu@...il.com,
        guoren@...nel.org, jonas@...thpole.se, kernelfans@...il.com,
        linux-arm-kernel@...ts.infradead.org, linux@...linux.org.uk,
        nickhu@...estech.com, palmer@...belt.com, paulmck@...nel.org,
        paul.walmsley@...ive.com, peterz@...radead.org, shorne@...il.com,
        stefan.kristiansson@...nalahti.fi, tglx@...utronix.de,
        torvalds@...ux-foundation.org, tsbogend@...ha.franken.de,
        vgupta@...nel.org, will@...nel.org
Subject: Re: [PATCH 04/15] irq: simplify handle_domain_{irq,nmi}()

On Thu, 21 Oct 2021 19:02:25 +0100,
Mark Rutland <mark.rutland@....com> wrote:
> 
> There's no need for handle_domain_{irq,nmi}() to open-code the NULL
> check performed by handle_irq_desc(), nor the resolution of the desc
> performed by generic_handle_domain_irq().
> 
> Use generic_handle_domain_irq() directly, as this is functioanlly
> equivalent and clearer. At the same time, delete the stale comments,
> which are no longer helpful.
> 
> There should be no functional change as a result of this patch.
> 
> Signed-off-by: Mark Rutland <mark.rutland@....com>
> Cc: Marc Zyngier <maz@...nel.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> ---
>  kernel/irq/irqdesc.c | 24 ++++--------------------
>  1 file changed, 4 insertions(+), 20 deletions(-)
> 
> diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
> index 4e3c29bb603c..b07d0e1552bc 100644
> --- a/kernel/irq/irqdesc.c
> +++ b/kernel/irq/irqdesc.c
> @@ -690,17 +690,11 @@ int handle_domain_irq(struct irq_domain *domain,
>  		      unsigned int hwirq, struct pt_regs *regs)
>  {
>  	struct pt_regs *old_regs = set_irq_regs(regs);
> -	struct irq_desc *desc;
> -	int ret = 0;
> +	int ret;
>  
>  	irq_enter();
>  
> -	/* The irqdomain code provides boundary checks */
> -	desc = irq_resolve_mapping(domain, hwirq);
> -	if (likely(desc))
> -		handle_irq_desc(desc);
> -	else
> -		ret = -EINVAL;
> +	ret = generic_handle_domain_irq(domain, hwirq);
>  
>  	irq_exit();
>  	set_irq_regs(old_regs);
> @@ -721,24 +715,14 @@ int handle_domain_nmi(struct irq_domain *domain, unsigned int hwirq,
>  		      struct pt_regs *regs)
>  {
>  	struct pt_regs *old_regs = set_irq_regs(regs);
> -	struct irq_desc *desc;
> -	int ret = 0;
> +	int ret;
>  
>  	/*
>  	 * NMI context needs to be setup earlier in order to deal with tracing.
>  	 */
>  	WARN_ON(!in_nmi());
>  
> -	desc = irq_resolve_mapping(domain, hwirq);
> -
> -	/*
> -	 * ack_bad_irq is not NMI-safe, just report
> -	 * an invalid interrupt.
> -	 */
> -	if (likely(desc))
> -		handle_irq_desc(desc);
> -	else
> -		ret = -EINVAL;
> +	ret = generic_handle_domain_irq(domain, hwirq);
>  
>  	set_irq_regs(old_regs);
>  	return ret;

Yup, that's really neat. I somehow missed that when I moved some of
the legacy stuff to be ARM specific.

On a vaguely related note, I think you can drop the EXPORT_SYMBOL_GPL
on handle_irq_desc() now.

	M.

-- 
Without deviation from the norm, progress is not possible.