linux-kernel - [PATCH v2] checkpatch: check for nested unlikely calls

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Message-Id: <20190828133256.13630-1-efremov@linux.com>
Date:   Wed, 28 Aug 2019 16:32:56 +0300
From:   Denis Efremov <efremov@...ux.com>
To:     Andy Whitcroft <apw@...onical.com>, Joe Perches <joe@...ches.com>
Cc:     Denis Efremov <efremov@...ux.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2] checkpatch: check for nested unlikely calls

IS_ERR, IS_ERR_OR_NULL, IS_ERR_VALUE already contain unlikely optimization
internally. Thus, there is no point in calling these functions under
likely/unlikely.

This check is based on the coccinelle rule developed by Enrico Weigelt
https://lore.kernel.org/lkml/1559767582-11081-1-git-send-email-info@metux.net/

Signed-off-by: Denis Efremov <efremov@...ux.com>
---
 scripts/checkpatch.pl | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 93a7edfe0f05..55b90e1334d2 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -6480,6 +6480,12 @@ sub process {
 			     "Using $1 should generally have parentheses around the comparison\n" . $herecurr);
 		}
 
+# nested likely/unlikely calls
+		if ($line =~ /\b(?:(?:un)?likely)\s*\(!?\s*(IS_ERR(?:_OR_NULL|_VALUE)?)/) {
+			WARN("LIKELY_MISUSE",
+			     "nested (un)?likely calls, unlikely already used in $1 internally\n" . $herecurr);
+		}
+
 # whine mightly about in_atomic
 		if ($line =~ /\bin_atomic\s*\(/) {
 			if ($realfile =~ m@...ivers/@) {
-- 
2.21.0