linux-kernel - Re: [PATCH 1/2] powerpc: Make the code in __show

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Date:   Thu, 22 Apr 2021 17:27:14 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Xiongwei Song <sxwjean@...com>, mpe@...erman.id.au,
        benh@...nel.crashing.org, paulus@...ba.org, npiggin@...il.com,
        ravi.bangoria@...ux.ibm.com, mikey@...ling.org,
        aneesh.kumar@...ux.ibm.com, 0x7f454c46@...il.com
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Xiongwei Song <sxwjean@...il.com>
Subject: Re: [PATCH 1/2] powerpc: Make the code in __show_regs nice-looking



Le 22/04/2021 à 17:10, Xiongwei Song a écrit :
> From: Xiongwei Song <sxwjean@...il.com>
> 
> Create a new function named interrupt_detail_printable to judge which
> interrupts can print esr/dsisr register.

What is the benefit of that function ? It may be interesting if the test was done at several places, 
but as it is done at only one place, I don't thing it is an improvement.

Until know, you new immediately what was the traps that would print it. Now you have to go and look 
into a sub-function.

And the name is not nice either. All other functions testing anything on the trap type are called 
trap_is_something()

Here your function would be better called something like trap_sets_dsisr()

> 
> Signed-off-by: Xiongwei Song <sxwjean@...il.com>
> ---
>   arch/powerpc/kernel/process.c | 21 ++++++++++++++++-----
>   1 file changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index 89e34aa273e2..5c3830837f3a 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -1453,9 +1453,23 @@ static void print_msr_bits(unsigned long val)
>   #define REGS_PER_LINE	8
>   #endif
>   
> +static bool interrupt_detail_printable(int trap)
> +{
> +	switch (trap) {
> +	case INTERRUPT_MACHINE_CHECK:
> +	case INTERRUPT_DATA_STORAGE:
> +	case INTERRUPT_ALIGNMENT:
> +		return true;
> +	default:
> +		return false;
> +	}
> +
> +	return false;

That's redundant with the default case inside the switch.

> +}
> +
>   static void __show_regs(struct pt_regs *regs)
>   {
> -	int i, trap;
> +	int i;
>   
>   	printk("NIP:  "REG" LR: "REG" CTR: "REG"\n",
>   	       regs->nip, regs->link, regs->ctr);
> @@ -1464,12 +1478,9 @@ static void __show_regs(struct pt_regs *regs)
>   	printk("MSR:  "REG" ", regs->msr);
>   	print_msr_bits(regs->msr);
>   	pr_cont("  CR: %08lx  XER: %08lx\n", regs->ccr, regs->xer);
> -	trap = TRAP(regs);
>   	if (!trap_is_syscall(regs) && cpu_has_feature(CPU_FTR_CFAR))
>   		pr_cont("CFAR: "REG" ", regs->orig_gpr3);
> -	if (trap == INTERRUPT_MACHINE_CHECK ||
> -	    trap == INTERRUPT_DATA_STORAGE ||
> -	    trap == INTERRUPT_ALIGNMENT) {
> +	if (interrupt_detail_printable(TRAP(regs))) {
>   		if (IS_ENABLED(CONFIG_4xx) || IS_ENABLED(CONFIG_BOOKE))
>   			pr_cont("DEAR: "REG" ESR: "REG" ", regs->dar, regs->dsisr);
>   		else
>