checkpatch: check for nested (un)?likely() calls

IS_ERR(), IS_ERR_OR_NULL(), IS_ERR_VALUE() and WARN*() already contain
unlikely() optimization internally.  Thus, there is no point in calling
these functions and defines under likely()/unlikely().

This check is based on the coccinelle rule developed by Enrico Weigelt
https://lore.kernel.org/lkml/[email protected]/

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Denis Efremov <[email protected]>
Cc: Joe Perches <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: Anton Altaparmakov <[email protected]>
Cc: Boris Ostrovsky <[email protected]>
Cc: Boris Pismenny <[email protected]>
Cc: Darrick J. Wong <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Denis Efremov <[email protected]>
Cc: Dennis Dalessandro <[email protected]>
Cc: Inaky Perez-Gonzalez <[email protected]>
Cc: Juergen Gross <[email protected]>
Cc: Leon Romanovsky <[email protected]>
Cc: Mike Marciniszyn <[email protected]>
Cc: Rob Clark <[email protected]>
Cc: Saeed Mahameed <[email protected]>
Cc: Sean Paul <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 6 insertions, 0 deletions

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 4eb355d8ae73..6fcc66afb088 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -6507,6 +6507,12 @@ sub process {
 			     "Using $1 should generally have parentheses around the comparison\n" . $herecurr);
 		}
 
+# nested likely/unlikely calls
+		if ($line =~ /\b(?:(?:un)?likely)\s*\(\s*!?\s*(IS_ERR(?:_OR_NULL|_VALUE)?|WARN)/) {
+			WARN("LIKELY_MISUSE",
+			     "nested (un)?likely() calls, $1 already uses unlikely() internally\n" . $herecurr);
+		}
+
 # whine mightly about in_atomic
 		if ($line =~ /\bin_atomic\s*\(/) {
 			if ($realfile =~ m@^drivers/@) {