linux-kernel - Re: [tip:locking/core] locking/atomics: Simplify the op definitions in atomic.h some more

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Date:   Tue, 15 May 2018 19:10:21 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        akpm@...ux-foundation.org, will.deacon@....com,
        torvalds@...ux-foundation.org, paulmck@...ux.vnet.ibm.com,
        tglx@...utronix.de, hpa@...or.com,
        linux-tip-commits@...r.kernel.org
Subject: Re: [tip:locking/core] locking/atomics: Simplify the op definitions
 in atomic.h some more

On Tue, May 15, 2018 at 04:43:33PM +0100, Mark Rutland wrote:
> I put together the following while trying to avoid bash magic (i.e the
> arrays, and keeping the option of naming the params. My local copy of
> dash seems happy with it.

Very nice; clearly your sh foo is stronger than mine ;-)

> I *think* the table can encode enough info to generate atomic-long.h,
> atomic-instrumented.h, and the atomic.h ordering fallbacks. I'll need to
> flesh out the table and check that we don't end up clashing with
> some of the regular fallbacks.

Yes, details details ;-)

> # name	meta	args...
> #
> # Where meta contains a string of:
> # * B - bool: returns bool, fully ordered
> # * V - void: returns void, fully ordered

void retuns are relaxed

> # * I - int: returns base type, all orderings
> # * R - return: returns base type, all orderings
> # * F - fetch: returns base type, all orderings
> # * T - try: returns bool, all orderings

Little more verbose than mine, I think we can get there with X and XB
instead of I and T, but whatever :-)

> # Where args contains list of type[:name], where type is:
> # * v - pointer to atomic base type (atomic or atomic64)
> # * i - base type (int or long)
> # * I - pointer to base type (int or long)
> #
> add		VRF	i	v
> sub		VRF	i	v
> inc		VRF	v
> dec		VRF	v
> or		VF	i	v
> and		VF	i	v
> andnot		VF	i	v
> xor		VF	i	v
> xchg		I	v	i
> cmpxchg		I	v	i:old	i:new
> try_cmpxchg	T	v	I:old	i:new
> add_and_test	B	i	v
> sub_and_test	B	i	v
> dec_and_test	B	v
> inc_and_test	B	v

Cute, that [:name].