linux-kernel - Re: [PATCH 1/5] x86/percpu: Differentiate this_cpu_{}() and __this_cpu

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Message-ID: <20190227173422.GV32494@hirez.programming.kicks-ass.net>
Date:   Wed, 27 Feb 2019 18:34:22 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrew Lutomirski <luto@...nel.org>,
        Nadav Amit <namit@...are.com>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Nadav Amit <nadav.amit@...il.com>
Subject: Re: [PATCH 1/5] x86/percpu: Differentiate this_cpu_{}() and
 __this_cpu_{}()

On Wed, Feb 27, 2019 at 09:17:42AM -0800, Linus Torvalds wrote:
> It all seems pretty ad-hoc, and we already _know_ that "asm volatile" is bad.

Ah, all I wanted was the ONCE thing and my inline asm foo sucks. If +m
gets us that, awesome.

But the ONCE thing defeats CSE (on purpose!) so for code-gen that
likes/wants that we then have to use the __this_cpu crud.