linux-kernel - Re: [PATCH v2 17/17] irq: remove handle_domain

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Message-ID: <20220506203242.GA1855@wunner.de>
Date:   Fri, 6 May 2022 22:32:42 +0200
From:   Lukas Wunner <lukas@...ner.de>
To:     Mark Rutland <mark.rutland@....com>, maz@...nel.org,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        linux-gpio@...r.kernel.org,
        Octavian Purdila <octavian.purdila@....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, paul.walmsley@...ive.com,
        shorne@...il.com, stefan.kristiansson@...nalahti.fi,
        tglx@...utronix.de, tsbogend@...ha.franken.de, vgupta@...nel.org,
        vladimir.murzin@....com, will@...nel.org
Subject: Re: [PATCH v2 17/17] irq: remove handle_domain_{irq,nmi}()

On Tue, Oct 26, 2021 at 10:25:04AM +0100, Mark Rutland wrote:
> Now that entry code handles IRQ entry (including setting the IRQ regs)
> before calling irqchip code, irqchip code can safely call
> generic_handle_domain_irq(), and there's no functional reason for it to
> call handle_domain_irq().
> 
> Let's cement this split of responsibility and remove handle_domain_irq()
> entirely, updating irqchip drivers to call generic_handle_domain_irq().
> 
> For consistency, handle_domain_nmi() is similarly removed and replaced
> with a generic_handle_domain_nmi() function which also does not perform
> any entry logic.
> 
> Previously handle_domain_{irq,nmi}() had a WARN_ON() which would fire
> when they were called in an inappropriate context. So that we can
> identify similar issues going forward, similar WARN_ON_ONCE() logic is
> added to the generic_handle_*() functions, and comments are updated for
> clarity and consistency.
[...]
>  int generic_handle_domain_irq(struct irq_domain *domain, unsigned int hwirq)
>  {
> +	WARN_ON_ONCE(!in_irq());
>  	return handle_irq_desc(irq_resolve_mapping(domain, hwirq));
>  }
>  EXPORT_SYMBOL_GPL(generic_handle_domain_irq);

Why isn't the WARN_ON_ONCE() conditional on handle_enforce_irqctx()?
(See handle_irq_desc() and c16816acd086.)

I believe the above change causes a regression in drivers/gpio/gpio-dln2.c
such that a gratuitous WARN splat is now emitted.

Thanks,

Lukas