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

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Message-ID: <20180515175307.m4xbkbicdrzo4qhb@lakrids.cambridge.arm.com>
Date:   Tue, 15 May 2018 18:53:08 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Peter Zijlstra <peterz@...radead.org>
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 07:10:21PM +0200, Peter Zijlstra wrote:
> On Tue, May 15, 2018 at 04:43:33PM +0100, Mark Rutland wrote:
> > 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

How about:

  V - void: returns void, no ordering variants (implicitly 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 :-)

Mhmm. I found it easier to do switch-like things this way, but it works
regardless.

> > # 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].

:D

Thanks,
Mark.