checkpatch: add likely/unlikely comparison misuse test

JoePerches · torvalds · commit acd9362c248e · 2015-02-13T21:21:39.000-08:00
Add a test for probably likely/unlikely misuses where the comparison is
likely misplaced

	if (likely(foo) &gt; 0)
vs
	if (likely(foo &gt; 0))

Signed-off-by: Joe Perches &lt;joe@perches.com&gt;
Cc: Christoph Jaeger &lt;cj@linux.com&gt;
Cc: Julia Lawall &lt;julia.lawall@lip6.fr&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
@@ -5239,6 +5239,13 @@ sub process {
 			      "#define of '$1' is wrong - use Kconfig variables or standard guards instead\n" . $herecurr);
 		}
 
+# likely/unlikely comparisons similar to "(likely(foo) > 0)"
+		if ($^V && $^V ge 5.10.0 &&
+		    $line =~ /\b((?:un)?likely)\s*\(\s*$FuncArg\s*\)\s*$Compare/) {
+			WARN("LIKELY_MISUSE",
+			     "Using $1 should generally have parentheses around the comparison\n" . $herecurr);
+		}
+
 # whine mightly about in_atomic
 		if ($line =~ /\bin_atomic\s*\(/) {
 			if ($realfile =~ m@^drivers/@) {
