linux-kernel - Re: [PATCH] x86/percpu: Fix and improve x86_this_cpu_test

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Date: Thu, 4 Apr 2024 10:48:22 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Uros Bizjak <ubizjak@...il.com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org,
	Andy Lutomirski <luto@...nel.org>, Brian Gerst <brgerst@...il.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	"H . Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH] x86/percpu: Fix and improve x86_this_cpu_test_bit() and
 friends


* Uros Bizjak <ubizjak@...il.com> wrote:

> Fix x86_this_cpu_variable_test_bit(), which is implemented with
> wrong asm template, where argument 2 (count argument) is considered
> as percpu variable. However, x86_this_cpu_test_bit() is currently
> used exclusively with constant bit number argument, so the called
> x86_this_cpu_variable_test_bit() function is never instantiated.
> The fix introduces named assembler operands to prevent this kind
> of errors.
> 
> Also rewrite the whole family of x86_this_cpu_test_bit() functions
> as macros, so standard __my_cpu_var() and raw_cpu_read() macros
> can be used on percpu variables. This approach considerably
> simplifies implementation of functions and also introduces standard
> checks on accessed percpu variables.
> 
> No functional changes intended.

Could you please split this into at least two patches?

Hint: 'also' in a changelog paragraph is an indicator of a new patch 
being justified, in like 80% of the cases. :-)

Thanks,

	Ingo