linux-kernel - Re: [PATCH v4] modpost: check for static EXPORT

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Date:   Thu, 1 Aug 2019 11:20:59 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Denis Efremov <efremov@...ux.com>
Cc:     Michal Marek <michal.lkml@...kovi.net>,
        Emil Velikov <emil.l.velikov@...il.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] modpost: check for static EXPORT_SYMBOL* functions

On Wed, Jul 31, 2019 at 5:54 PM Masahiro Yamada
<yamada.masahiro@...ionext.com> wrote:
>
> Hi.
>
>
>
> On Wed, Jul 31, 2019 at 3:12 AM Denis Efremov <efremov@...ux.com> wrote:
> >
> > This patch adds a check to warn about static EXPORT_SYMBOL* functions
> > during the modpost. In most of the cases, a static symbol marked for
> > exporting is an odd combination that should be fixed either by deleting
> > the exporting mark or by removing the static attribute and adding the
> > appropriate declaration to headers.
> >
> > This check could help to detect the following problems:
> > 1. 550113d4e9f5 ("i2c: add newly exported functions to the header, too")
> > 2. 54638c6eaf44 ("net: phy: make exported variables non-static")
> > 3. 98ef2046f28b ("mm: remove the exporting of totalram_pages")
> > 4. 73df167c819e ("s390/zcrypt: remove the exporting of ap_query_configuration")
> > 5. a57caf8c527f ("sunrpc/cache: remove the exporting of cache_seq_next")
> > 6. e4e4730698c9 ("crypto: skcipher - remove the exporting of skcipher_walk_next")
> > 7. 14b4c48bb1ce ("gve: Remove the exporting of gve_probe")
> > 8. 9b79ee9773a8 ("scsi: libsas: remove the exporting of sas_wait_eh")
> > 9. ...
> >
> > Build time impact, allmodconfig, Dell XPS 15 9570 (measurements 3x):
> > $ make mrproper; make allmodconfig; time make -j12; \
> >   git checkout HEAD~1; \
> >   make mrproper; make allmodconfig; time make -j12
> > 1.
> >    (with patch) 17635,94s user 1895,54s system 1085% cpu 29:59,22 total
> >    (w/o  patch) 17275,42s user 1803,87s system 1112% cpu 28:35,66 total
> > 2.
> >    (with patch) 17369,51s user 1763,28s system 1111% cpu 28:41,47 total
> >    (w/o  patch) 16880,50s user 1670,93s system 1113% cpu 27:46,56 total
> > 3.
> >    (with patch) 17937,88s user 1842,53s system 1109% cpu 29:42,26 total
> >    (w/o  patch) 17267,55s user 1725,09s system 1111% cpu 28:28,17 total
> >
> > The check adds less than a minute to a usual build.

The build time impact is very limited.
I guess this measurement is unnecessary in the commit log.


-- 
Best Regards
Masahiro Yamada