linux-kernel - Re: [RFC PATCH 3/3] x86/cpufeature: Remove unused and seldomly used cpu_has

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Message-ID: <20151110123000.GA20227@gmail.com>
Date:	Tue, 10 Nov 2015 13:30:00 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Borislav Petkov <bp@...en8.de>
Cc:	X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andy Lutomirski <luto@...capital.net>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Matt Mackall <mpm@...enic.com>, Chris Mason <clm@...com>,
	Josef Bacik <jbacik@...com>, David Sterba <dsterba@...e.com>
Subject: Re: [RFC PATCH 3/3] x86/cpufeature: Remove unused and seldomly used
 cpu_has_xx macros

* Borislav Petkov <bp@...en8.de> wrote:

> From: Borislav Petkov <bp@...e.de>
> 
> Those are stupid and code should use static_cpu_has_safe() anyway. Kill
> the least used and unused ones.

So cpufeature.h doesn't really do a good job of explaining what the difference is 
between all these variants:

	cpu_has()
	static_cpu_has()
	static_cpu_has_safe()

it has this comment:

/*
 * Static testing of CPU features.  Used the same as boot_cpu_has().
 * These are only valid after alternatives have run, but will statically
 * patch the target code for additional performance.
 */

The second sentence does not parse. Why does the third sentence have a 'but' for 
listing properties? It's either bad grammer or tries to tell something that isn't 
being told properly.

It's entirely silent on the difference between static_cpu_has() and 
static_cpu_has_safe() - what makes the second one 'safe'?

Thanks,

	Ingo
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