linux-kernel - Re: [PATCH 0/7] atomics: generate atomic headers

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Date:   Tue, 5 Jun 2018 15:29:49 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     linux-kernel@...r.kernel.org, boqun.feng@...il.com,
        will.deacon@....com, arnd@...db.de, aryabinin@...tuozzo.com,
        dvyukov@...gle.com, glider@...gle.com, gregkh@...uxfoundation.org,
        jslaby@...e.com, parri.andrea@...il.com
Subject: Re: [PATCH 0/7] atomics: generate atomic headers

On Tue, May 29, 2018 at 07:07:39PM +0100, Mark Rutland wrote:
> Longer-term, I think things could be simplified if we were to rework the
> headers such that we have:
> 
> * arch/*/include/asm/atomic.h providing arch_atomic_*().
> 
> * include/linux/atomic-raw.h building raw_atomic_*() atop of the
>   arch_atomic_*() definitions, filling in gaps in the API. Having
>   separate arch_ and raw_ namespaces would simplify the ifdeffery.
> 
> * include/linux/atomic.h building atomic_*() atop of the raw_atomic_*()
>   definitions, complete with any instrumentation. Instrumenting at this
>   level would lower the instrumentation overhead, and would not require
>   any ifdeffery as the whole raw_atomic_*() API would be available.
> 
> ... I've avoided this for the time being due to the necessary churn in
> arch code.

I'm not entirely sure I get the point of raw_atomic, we only need to
instrument the arch_atomic bits, right? When those are done, everything
that's build on top will also automagically be instrumented.