linux-kernel - [PATCH] checkpatch: allow an assignment in if condition for ACQUIRE

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Message-ID: <20250813003821.2891532-1-alison.schofield@intel.com>
Date: Tue, 12 Aug 2025 17:38:19 -0700
From: alison.schofield@...el.com
To: Andy Whitcroft <apw@...onical.com>,
	Joe Perches <joe@...ches.com>,
	Dwaipayan Ray <dwaipayanray1@...il.com>,
	Lukas Bulwahn <lukas.bulwahn@...il.com>
Cc: Alison Schofield <alison.schofield@...el.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Dan Williams <dan.j.williams@...el.com>,
	linux-cxl@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] checkpatch: allow an assignment in if condition for ACQUIRE_ERR()

From: Alison Schofield <alison.schofield@...el.com>

New helpers, ACQUIRE() and ACQUIRE_ERR(), were recently introduced to
clean up conditional locking paths [1].

That led to checkpatch ERRORS:
        ERROR: do not use assignment in if condition

on usages like this:
        ACQUIRE(rwsem_write_kill, rwsem)(&cxl_rwsem.region);
        if ((rc = ACQUIRE_ERR(rwsem_write_kill, &rwsem)))
                return rc;

That compact format was a deliberate choice by the authors. By making
this a checkpatch exception, existing ERRORs are quieted, and future
users of the macro will not be dissuaded by checkpatch from using the
preferred compact format.

[1] Commit d03fcf50ba56 ("cxl: Convert to ACQUIRE() for conditional rwsem locking")

Signed-off-by: Alison Schofield <alison.schofield@...el.com>
---
 scripts/checkpatch.pl | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index e722dd6fa8ef..150f355c632e 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5696,7 +5696,14 @@ sub process {
 			my ($s, $c) = ($stat, $cond);
 			my $fixed_assign_in_if = 0;
 
-			if ($c =~ /\bif\s*\(.*[^<>!=]=[^=].*/s) {
+			if ($c =~ /\bif\s*\((.*[^<>!=]=[^=].*)\)/s) {
+				my $expr = $1;
+
+				# Allow ACQUIRE_ERR() macro syntax
+				if ($expr =~ /\w+\s*=\s*ACQUIRE_ERR\s*\(/) {
+					next;
+				}
+
 				if (ERROR("ASSIGN_IN_IF",
 					  "do not use assignment in if condition\n" . $herecurr) &&
 				    $fix && $perl_version_ok) {
-- 
2.37.3