linux-kernel - Re: [PATCH v2 2/7] docs: kdoc: micro-optimize KernRe

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250704080140.136b0b38@foz.lan>
Date: Fri, 4 Jul 2025 08:01:40 +0200
From: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
To: Jonathan Corbet <corbet@....net>
Cc: linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, Akira Yokosawa
 <akiyks@...il.com>
Subject: Re: [PATCH v2 2/7] docs: kdoc: micro-optimize KernRe

Em Thu, 03 Jul 2025 17:47:13 -0600
Jonathan Corbet <corbet@....net> escreveu:

> Mauro Carvalho Chehab <mchehab+huawei@...nel.org> writes:
> 
> > Em Thu,  3 Jul 2025 12:43:58 -0600
> > Jonathan Corbet <corbet@....net> escreveu:
> >  
> >> Rework _add_regex() to avoid doing the lookup twice for the (hopefully
> >> common) cache-hit case.
> >> 
> >> Signed-off-by: Jonathan Corbet <corbet@....net>
> >> ---
> >>  scripts/lib/kdoc/kdoc_re.py | 7 ++-----
> >>  1 file changed, 2 insertions(+), 5 deletions(-)
> >> 
> >> diff --git a/scripts/lib/kdoc/kdoc_re.py b/scripts/lib/kdoc/kdoc_re.py
> >> index e81695b273bf..612223e1e723 100644
> >> --- a/scripts/lib/kdoc/kdoc_re.py
> >> +++ b/scripts/lib/kdoc/kdoc_re.py
> >> @@ -29,12 +29,9 @@ class KernRe:
> >>          """
> >>          Adds a new regex or re-use it from the cache.
> >>          """
> >> -
> >> -        if string in re_cache:
> >> -            self.regex = re_cache[string]
> >> -        else:
> >> +        self.regex = re_cache.get(string, None)  
> >
> > With get, None is default...
> >  
> >> +        if not self.regex:
> >>              self.regex = re.compile(string, flags=flags)  
> >
> > ... yet, as you're using get, better to code it as:
> >
> > 	self.regex = re_cache.get(string, re.compile(string, flags=flags))  
> 
> ...but that will recompile the regex each time, defeating the purpose of
> the cache, no?

No. It should do exactly like the previous code:

- if re_cache[string] exists, it returns it. 
- Otherwise, it returns re.compile(string, flags=flags).

https://www.w3schools.com/python/ref_dictionary_get.asp


Thanks,
Mauro