linux-kernel - Re: [PATCH] m68k: mac: Remove forward declaration for mac_nmi

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Date:   Thu, 7 Jul 2022 12:11:33 +1000 (AEST)
From:   Finn Thain <fthain@...ux-m68k.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
cc:     linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] m68k: mac: Remove forward declaration for
 mac_nmi_handler()

On Wed, 6 Jul 2022, Geert Uytterhoeven wrote:

> Move mac_nmi_handler() before its caller, so its forward declaration can
> be dropped.  While at it, make the function static, and absorb the
> variable in_nmi, which is only used inside the function.
> 
> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>

Reviewed-by: Finn Thain <fthain@...ux-m68k.org>

BTW, this code needs the race condition fixed but I think that would 
require CONFIG_ADVANCED && CONFIG_RMW_INSNS, and arch/m68k/Kconfig.cpu 
advises against it. There is some discussion of Amiga and Atari in 
relation to RMW and it's claimed "it is also said to destabilize other 
machines" which may be true but doesn't help much.

> ---
> To be queued in the m68k tree for v5.20.
> 
>  arch/m68k/mac/macints.c | 32 +++++++++++++++-----------------
>  1 file changed, 15 insertions(+), 17 deletions(-)
> 
> diff --git a/arch/m68k/mac/macints.c b/arch/m68k/mac/macints.c
> index e3575388cd05a8cc..883e48230f87a187 100644
> --- a/arch/m68k/mac/macints.c
> +++ b/arch/m68k/mac/macints.c
> @@ -129,8 +129,6 @@
>  
>  extern void show_registers(struct pt_regs *);
>  
> -irqreturn_t mac_nmi_handler(int, void *);
> -
>  static unsigned int mac_irq_startup(struct irq_data *);
>  static void mac_irq_shutdown(struct irq_data *);
>  
> @@ -142,6 +140,21 @@ static struct irq_chip mac_irq_chip = {
>  	.irq_shutdown	= mac_irq_shutdown,
>  };
>  
> +static irqreturn_t mac_nmi_handler(int irq, void *dev_id)
> +{
> +	static volatile int in_nmi;
> +
> +	if (in_nmi)
> +		return IRQ_HANDLED;
> +	in_nmi = 1;
> +
> +	pr_info("Non-Maskable Interrupt\n");
> +	show_registers(get_irq_regs());
> +
> +	in_nmi = 0;
> +	return IRQ_HANDLED;
> +}
> +
>  void __init mac_init_IRQ(void)
>  {
>  	m68k_setup_irq_controller(&mac_irq_chip, handle_simple_irq, IRQ_USER,
> @@ -254,18 +267,3 @@ static void mac_irq_shutdown(struct irq_data *data)
>  	else
>  		mac_irq_disable(data);
>  }
> -
> -static volatile int in_nmi;
> -
> -irqreturn_t mac_nmi_handler(int irq, void *dev_id)
> -{
> -	if (in_nmi)
> -		return IRQ_HANDLED;
> -	in_nmi = 1;
> -
> -	pr_info("Non-Maskable Interrupt\n");
> -	show_registers(get_irq_regs());
> -
> -	in_nmi = 0;
> -	return IRQ_HANDLED;
> -}
>