linux-kernel - Re: [PATCH v2] arm64: Refactor conditional logic

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Message-ID:
 <PN0P287MB2843A2EFD47FA629DBFD061FFF5B2@PN0P287MB2843.INDP287.PROD.OUTLOOK.COM>
Date: Thu, 14 Nov 2024 14:37:13 +0000
From: Hardevsinh Palaniya <hardevsinh.palaniya@...iconsignals.io>
To: "will@...nel.org" <will@...nel.org>, "broonie@...nel.org"
	<broonie@...nel.org>
CC: Catalin Marinas <catalin.marinas@....com>, Oliver Upton
	<oliver.upton@...ux.dev>, Marc Zyngier <maz@...nel.org>, Ard Biesheuvel
	<ardb@...nel.org>, Mark Rutland <mark.rutland@....com>, Joey Gouly
	<joey.gouly@....com>, Ryan Roberts <ryan.roberts@....com>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] arm64: Refactor conditional logic

Hi all,

> Unnecessarily checks ftr_ovr == tmp in an extra else if, which is not
> needed because that condition would already be true by default if the
> previous conditions are not satisfied.
>
>                if (ftr_ovr != tmp) {
>                } else if (ftr_new != tmp) {
>                } else if (ftr_ovr == tmp) {
>
> Logic: The first and last conditions are inverses of each other, so
> the last condition must be true if the first two conditions are false.
>
> Additionally, all branches set the variable str, making the subsequent
> "if (str)" check redundant
> 
> Reviewed-by: Mark Brown <broonie@...nel.org>
> Signed-off-by: Hardevsinh Palaniya <hardevsinh.palaniya@...iconsignals.io>

Please consider this patch as v3. Apologies for the inconvenience.

Best regards,
Hardev


________________________________________
From: Hardevsinh Palaniya <hardevsinh.palaniya@...iconsignals.io>
Sent: Thursday, November 14, 2024 7:52 PM
To: will@...nel.org <will@...nel.org>; broonie@...nel.org <broonie@...nel.org>
Cc: Hardevsinh Palaniya <hardevsinh.palaniya@...iconsignals.io>; Catalin Marinas <catalin.marinas@....com>; Oliver Upton <oliver.upton@...ux.dev>; Marc Zyngier <maz@...nel.org>; Ard Biesheuvel <ardb@...nel.org>; Mark Rutland <mark.rutland@....com>; Joey Gouly <joey.gouly@....com>; Ryan Roberts <ryan.roberts@....com>; linux-arm-kernel@...ts.infradead.org <linux-arm-kernel@...ts.infradead.org>; linux-kernel@...r.kernel.org <linux-kernel@...r.kernel.org>
Subject: [PATCH v2] arm64: Refactor conditional logic
 
Unnecessarily checks ftr_ovr == tmp in an extra else if, which is not
needed because that condition would already be true by default if the
previous conditions are not satisfied.

                if (ftr_ovr != tmp) {
                } else if (ftr_new != tmp) {
                } else if (ftr_ovr == tmp) {

Logic: The first and last conditions are inverses of each other, so
the last condition must be true if the first two conditions are false.

Additionally, all branches set the variable str, making the subsequent
"if (str)" check redundant

Reviewed-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Hardevsinh Palaniya <hardevsinh.palaniya@...iconsignals.io>
---

Changelog in V2:

- remove str check

Change in V3:

- Add logic in commit msg
- Add review tag
---
 arch/arm64/kernel/cpufeature.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 718728a85430..728709483fb7 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -989,17 +989,16 @@ static void init_cpu_ftr_reg(u32 sys_reg, u64 new)
                                 /* Override was valid */
                                 ftr_new = tmp;
                                 str = "forced";
-                       } else if (ftr_ovr == tmp) {
+                       } else {
                                 /* Override was the safe value */
                                 str = "already set";
                         }
 
-                       if (str)
-                               pr_warn("%s[%d:%d]: %s to %llx\n",
-                                       reg->name,
-                                       ftrp->shift + ftrp->width - 1,
-                                       ftrp->shift, str,
-                                       tmp & (BIT(ftrp->width) - 1));
+                       pr_warn("%s[%d:%d]: %s to %llx\n",
+                               reg->name,
+                               ftrp->shift + ftrp->width - 1,
+                               ftrp->shift, str,
+                               tmp & (BIT(ftrp->width) - 1));
                 } else if ((ftr_mask & reg->override->val) == ftr_mask) {
                         reg->override->val &= ~ftr_mask;
                         pr_warn("%s[%d:%d]: impossible override, ignored\n",
--
2.43.0