[PATCH] checkpatch: Whine about ACCESS_ONCE

[Joe Perches <joe@perches.com>]

Add a test for use of ACCESS_ONCE that could be written using
READ_ONCE or WRITE_ONCE.

--fix it too if desired.

Signed-off-by: Joe Perches <joe@perches.com>
---
 scripts/checkpatch.pl | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index e3d9c34..5e5d2a4 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5837,6 +5837,28 @@ sub process {
 			}
 		}
 
+# whine about ACCESS_ONCE
+		if ($^V && $^V ge 5.10.0 &&
+		    $line =~ /\bACCESS_ONCE\s*$balanced_parens\s*(=(?!=))?\s*($FuncArg)?/) {
+			my $par = $1;
+			my $eq = $2;
+			my $fun = $3;
+			$par =~ s/^\(\s*(.*)\s*\)$/$1/;
+			if (defined($eq)) {
+				if (WARN("PREFER_WRITE_ONCE",
+					 "Prefer WRITE_ONCE(<FOO>, <BAR>) over ACCESS_ONCE(<FOO>) = <BAR>\n" . $herecurr) &&
+				    $fix) {
+					$fixed[$fixlinenr] =~ s/\bACCESS_ONCE\s*\(\s*\Q$par\E\s*\)\s*$eq\s*\Q$fun\E/WRITE_ONCE($par, $fun)/;
+				}
+			} else {
+				if (WARN("PREFER_READ_ONCE",
+					 "Prefer READ_ONCE(<FOO>) over ACCESS_ONCE(<FOO>)\n" . $herecurr) &&
+				    $fix) {
+					$fixed[$fixlinenr] =~ s/\bACCESS_ONCE\s*\(\s*\Q$par\E\s*\)/READ_ONCE($par)/;
+				}
+			}
+		}
+
 # check for lockdep_set_novalidate_class
 		if ($line =~ /^.\s*lockdep_set_novalidate_class\s*\(/ ||
 		    $line =~ /__lockdep_no_validate__\s*\)/ ) {