linux-kernel - Re: [PATCH 2/2] module: add support to avoid duplicates early on load

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Date:   Sun, 4 Jun 2023 14:26:12 +0000
From:   Rudi Heitbaum <rudi@...tbaum.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Johan Hovold <johan@...nel.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Lucas De Marchi <lucas.demarchi@...el.com>,
        Petr Pavlu <petr.pavlu@...e.com>, gregkh@...uxfoundation.org,
        rafael@...nel.org, song@...nel.org, lucas.de.marchi@...il.com,
        christophe.leroy@...roup.eu, peterz@...radead.org, rppt@...nel.org,
        dave@...olabs.net, willy@...radead.org, vbabka@...e.cz,
        mhocko@...e.com, dave.hansen@...ux.intel.com,
        colin.i.king@...il.com, jim.cromie@...il.com,
        catalin.marinas@....com, jbaron@...mai.com,
        rick.p.edgecombe@...el.com, yujie.liu@...el.com, david@...hat.com,
        tglx@...utronix.de, hch@....de, patches@...ts.linux.dev,
        linux-modules@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, pmladek@...e.com, prarit@...hat.com,
        lennart@...ttering.net, imre.deak@...el.com
Subject: Re: [PATCH 2/2] module: add support to avoid duplicates early on load

On Mon, May 29, 2023 at 09:55:15PM -0400, Linus Torvalds wrote:
> On Mon, May 29, 2023 at 11:18 AM Johan Hovold <johan@...nel.org> wrote:
> >
> > I took a closer look at some of the modules that failed to load and
> > noticed a pattern in that they have dependencies that are needed by more
> > than one device.
> 
> Ok, this is a "maybe something like this" RFC series of two patches -
> one trivial one to re-organize things a bit so that we can then do the
> real one which uses a filter based on the inode pointer to return an
> "idempotent return value" for module loads that share the same inode.
> 
> It's entirely untested, and since I'm on the road I'm going to not
> really be able to test it. It compiles for me, and the code looks
> fairly straightforward, but it's probably buggy.

The updated patches fix the issue experienced with 6.4-rc4 where the Intel
NUC12 booted fine, but on media playback resulted in the video stuttering,
then freezing - and that audio was not coming though.

# diff modules-rc4 modules-rc4-patched
< snd_hda_codec_hdmi     77824  0
< snd_hda_codec_realtek   159744  0
---
> snd_hda_codec_hdmi     77824  1
> snd_hda_codec_realtek   159744  1

 Revert "module: error out early on concurrent load of the same module file"
 module: split up 'finit_module()' into init_module_from_file() helper
 modules: catch concurrent module loads, take two
 Johan's fix:
  -static struct spinlock idem_lock;
  +static DEFINE_SPINLOCK(idem_lock);

Tested-by: Rudi Heitbaum <rudi@...tbaum..com>