Re: [PATCH v2 1/3] base: mark 'no_warn' as unused - Greg Kroah-Hartman

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Nathan Chancellor <nathan@kernel.org>
Cc: Bill Wendling <morbo@google.com>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	clang-built-linux@googlegroups.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/3] base: mark 'no_warn' as unused
Date: Tue, 27 Jul 2021 07:27:23 +0200	[thread overview]
Message-ID: <YP+ZOx8BETgufxBS@kroah.com> (raw)
In-Reply-To: <c965006c-88e1-3265-eb9c-76dc0bbcb733@kernel.org>

On Mon, Jul 26, 2021 at 01:47:33PM -0700, Nathan Chancellor wrote:
> + Greg and Rafael as the maintainer and reviewer of drivers/base/module.c
> respectively, drop everyone else.

Odd no one cc:ed us originally, I guess they didn't want the patch ever
merged?  :(

> 
> Original post:
> 
> https://lore.kernel.org/r/20210726201924.3202278-2-morbo@google.com/
> 
> On 7/26/2021 1:19 PM, 'Bill Wendling' via Clang Built Linux wrote:
> > Fix the following build warning:
> > 
> >    drivers/base/module.c:36:6: error: variable 'no_warn' set but not used [-Werror,-Wunused-but-set-variable]
> >          int no_warn;

That's not going to be a good warning to ever have the kernel use due to
how lots of hardware works (i.e. we need to do a read after a write but
we can throw the read away as it does not matter).

> > 
> > This variable is used to remove another warning, but causes a warning
> > itself. Mark it as 'unused' to avoid that.
> > 
> > Signed-off-by: Bill Wendling <morbo@google.com>
> 
> Even though they evaluate to the same thing, it might be worth using
> "__always_unused" here because it is :)

But it is not unused, the value is written into it.

So this isn't ok, sometimes we want to write to variables but never care
about the value, that does not mean the compiler should complain about
it.

thanks,

greg k-h