linux-kernel - [PATCH] checkpatch: Reduce runtime/cpu time used

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Message-ID: <1376497253.1949.75.camel@joe-AO722>
Date:	Wed, 14 Aug 2013 09:20:53 -0700
From:	Joe Perches <joe@...ches.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Andy Whitcroft <apw@...onical.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] checkpatch: Reduce runtime/cpu time used

There are some cases where checkpatch can take
a long time to complete.  Reduce the likelihood
of this long run-time by adding a new test for
lines with and without comments and eliminating
checks on lines with only comments.

This reduces the number of "ctx_statement_block"
calls, and also the number of tests of $stat,
which is now undefined for these blank lines.

One test in particular, the "check for switch/default
statements without a break", could take an extremely
long time to parse as it tries to skip interleaving
comments within the ctx_statement_block/$stat and
that could be done multiple times unnecessarily.

A small test case taken from cfg80211.h before this
patch would take 1000's of seconds to run, now it's
just a couple seconds.

Signed-off-by: Joe Perches <joe@...ches.com>
---
 scripts/checkpatch.pl | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 3ba2db6..c9e01ab 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -1662,6 +1662,8 @@ sub process {
 	$linenr = 0;
 	foreach my $line (@lines) {
 		$linenr++;
+		my $sline = $line;	#copy of $line
+		$sline =~ s/$;/ /g;	#with comments as spaces

 		my $rawline = $rawlines[$linenr - 1];

@@ -2178,7 +2180,7 @@ sub process {
 		    $realline_next);
 #print "LINE<$line>\n";
 		if ($linenr >= $suppress_statement &&
-		    $realcnt && $line =~ /.\s*\S/) {
+		    $realcnt && $sline =~ /.\s*\S/) {
 			($stat, $cond, $line_nr_next, $remain_next, $off_next) =
 				ctx_statement_block($linenr, $realcnt, 0);
 			$stat =~ s/\n./\n /g;

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