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Date:   Fri, 24 Mar 2023 17:44:45 +0100
From:   Borislav Petkov <bp@alien8.de>
To:     John Ogness <john.ogness@linutronix.de>
Cc:     linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86/microcode: move @microcode_mutex definition near
 usage
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On Fri, Mar 24, 2023 at 05:39:35PM +0106, John Ogness wrote:
> Note that an unused mutex is being defined, even when the compiler is
> not warning about it.

Are you sure?

$ make arch/x86/kernel/cpu/microcode/core.s
grep microcode_mutex arch/x86/kernel/cpu/microcode/core.s
$ 
$ make CC=clang arch/x86/kernel/cpu/microcode/core.s
$ grep microcode_mutex arch/x86/kernel/cpu/microcode/core.s
$ 

Looks to me like it gets optimized away.

> OK, but the kernel test robots will probably beat me to it. ;-)

That's exactly the question: they haven't because this is not a new
situation. Their compilers are optimizing unused stuff away too.

:-)

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette