Re: [PATCH v1 1/1] platform/x86: ideapad-laptop: Make the scope_guard() clear of its scope
From: Nathan Chancellor
Date: Fri Sep 13 2024 - 19:33:35 EST
On Thu, Sep 05, 2024 at 08:16:01PM -0700, Josh Poimboeuf wrote:
> On Wed, Sep 04, 2024 at 01:26:11PM +0300, Andy Shevchenko wrote:
> > On Tue, Sep 03, 2024 at 09:52:01PM -0700, Josh Poimboeuf wrote:
> > > I'm not sure I buy that, we should look closer to understand what the
> > > issue is. Can you share the config and/or toolchain version(s) need to
> > > trigger the warning?
> >
> > .config is from the original report [1], toolchain is
> > Debian clang version 18.1.8 (9)
> > Target: x86_64-pc-linux-gnu
> > Thread model: posix
> > InstalledDir: /usr/bin
> >
> > (Just whatever Debian unstable provides)
> >
> > [1]: https://lore.kernel.org/oe-kbuild-all/202408290219.BrPO8twi-lkp@xxxxxxxxx/
>
> The warning is due to a (minor?) Clang bug, almost like it tried to
> optimize but didn't quite finish.
...
> In this case, mutex is an unconditional guard, so the constructor just
> returns the original value of '&priv->vpc_mutex'. So if the original
> '&priv->vpc_mutex' is never NULL, the condition would always be true.
Thanks a lot for that Josh. I have a somewhat trivial reproducer for the
clang folks to take a look at. I should have some time on Monday to get
that reported upstream and I will see if I can find anyone to take a
look at it.
For what it is worth, I don't think the workaround for this is too bad
and it seems like it only shows up with KCOV.
Cheers,
Nathan