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SubjectRe: checkpatch.pl is getting too slow
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On Sat, 2009-01-31 at 21:02 +0000, Andy Whitcroft wrote:
> On Sat, Jan 31, 2009 at 10:55:07AM -0800, Greg KH wrote:
> > Hi Andy,
> > I've noticed that checkpatch.pl is getting slower and slower when run on
> > a whole file, but yesterday I realized that it now is pretty much
> > unusable:
> >
> > $ time ./scripts/checkpatch.pl --file drivers/staging/uc2322/aten2011.c
> >
> > <snip>
> > total: 168 errors, 126 warnings, 3939 lines checked
> >
> > drivers/staging/uc2322/aten2011.c has style problems, please review. If any of these errors
> > are false positives report them to the maintainer, see
> > CHECKPATCH in MAINTAINERS.
> >
> > real 8m7.924s
> > user 8m7.058s
> > sys 0m0.116s
>
> That is scarey indeed. Something is very wrong in there if it went back
> to a more reasonable 10's of seconds with a few patches. I will have a
> look at the file you attached and see what I can find.
>
> Thanks for the heads up.

After some debugging it looks like it takes a long time to processes
lines similar to,

/*************************************
* Bit definitions for each register *
*************************************/
#define LCR_BITS_5 0x00 /* 5 bits/char */
#define LCR_BITS_6 0x01 /* 6 bits/char */
#define LCR_BITS_7 0x02 /* 7 bits/char */
#define LCR_BITS_8 0x03 /* 8 bits/char */
#define LCR_BITS_MASK 0x03 /* Mask for bits/char field */

There's a section in the code which has several of these. The processing
slows down when this expression matches repeatedly,

# Check for potential 'bare' types
my ($stat, $cond, $line_nr_next, $remain_next, $off_next);
if ($realcnt && $line =~ /.\s*\S/) {
($stat, $cond, $line_nr_next, $remain_next, $off_next) =
ctx_statement_block($linenr, $realcnt, 0);
and ctx_statement_block will process $realcnt lines trying to find a
complete block, and it has no concept of "define" so it just keep
processing until it's concept of a block ending.. That happens on each
"define" line in the file, which I think accounts for all the overhead.

I added the following temporary work around, which speeds things up
considerably. Just forcing it to only process one line at most.

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 45eb0ae..787423a 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -1357,7 +1357,7 @@ sub process {
my ($stat, $cond, $line_nr_next, $remain_next, $off_next);
if ($realcnt && $line =~ /.\s*\S/) {
($stat, $cond, $line_nr_next, $remain_next, $off_next) =
- ctx_statement_block($linenr, $realcnt, 0);
+ ctx_statement_block($linenr, 1, 0);
$stat =~ s/\n./\n /g;
$cond =~ s/\n./\n /g;




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