linux-kernel - Re: [PATCH v1 1/1] x86/percpu: Cast -1 to argument type when comparing in percpu_add

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Message-ID: <4b1a26b2-cccb-75d8-ee2f-f30ae211e598@gentwo.org>
Date: Tue, 22 Oct 2024 16:24:21 -0700 (PDT)
From: "Christoph Lameter (Ampere)" <cl@...two.org>
To: Dave Hansen <dave.hansen@...el.com>
cc: Peter Zijlstra <peterz@...radead.org>, 
    Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, 
    Ingo Molnar <mingo@...nel.org>, Uros Bizjak <ubizjak@...il.com>, 
    linux-mm@...ck.org, linux-kernel@...r.kernel.org, llvm@...ts.linux.dev, 
    Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>, 
    Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, 
    Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, 
    x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>, 
    Nathan Chancellor <nathan@...nel.org>, 
    Nick Desaulniers <ndesaulniers@...gle.com>, 
    Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>
Subject: Re: [PATCH v1 1/1] x86/percpu: Cast -1 to argument type when comparing
 in percpu_add_op()

On Tue, 22 Oct 2024, Dave Hansen wrote:

> So I think Peter's version was the best.  It shuts up clang and also
> preserves the existing (good) gcc 'sub' behavior.  I'll send it out for
> real in a bit, but I'm thinking of something like the attached patch.

The desired behavior is a "dec". "sub" has a longer op code AFAICT.

View attachment "0001-x86-percpu-Avoid-comparing-unsigned-types-to-1.patch" of type "text/x-patch" (3180 bytes)