linux-kernel - Re: [RFC local_t removal V1 1/4] Add add_local() and add_local

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Message-ID: <alpine.DEB.2.00.1001051620030.9108@router.home>
Date:	Tue, 5 Jan 2010 16:29:42 -0600 (CST)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Mike Frysinger <vapier.adi@...il.com>
cc:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [RFC local_t removal V1 1/4] Add add_local() and 
 add_local_return()

On Tue, 5 Jan 2010, Mike Frysinger wrote:

> On Tue, Jan 5, 2010 at 17:04, Christoph Lameter wrote:
> > --- /dev/null   1970-01-01 00:00:00.000000000 +0000
> > +++ linux-2.6/include/asm-generic/add-local.h   2010-01-05 15:36:02.000000000 -0600
> > @@ -0,0 +1,13 @@
> > +#ifndef __ASM_GENERIC_ADD_LOCAL_H
> > +#define __ASM_GENERIC_ADD_LOCAL_H
>
> needs comment header (blurb/copyright/license)

A simple small include file? Really?

> > +#define add_return_local(ptr, v)                                       \
> > +       ((__typeof__(*(ptr)))__add_return_local_generic((ptr),          \
> > +                       (unsigned long)(v), sizeof(*(ptr))))
> > +
> > +#define add_local(ptr, v) (void)__add_return_local_generic((ptr),      \
> > +                       (unsigned long)(v), sizeof(*(ptr)))
>
> the only difference here is the cast ... perhaps define an
> _add_local() macro to avoid the duplication

Right. This is a shortcut to define the add_local() operation without too
much effort. We should be using add / inc /dec there at some point.

> > --- /dev/null   1970-01-01 00:00:00.000000000 +0000
> > +++ linux-2.6/arch/alpha/include/asm/add-local.h        2010-01-05 15:36:02.000000000 -0600
> > @@ -0,0 +1,2 @@
> > +#include <asm-generic/add-local.h>
> > +
>
> these arch stubs all have an extra new line

Thats bad?

> > +/*
> > + * Generic version of __add_return_local (disables interrupts). Takes an
> > + * unsigned long parameter, supporting various types of architectures.
> > + */
> > +static inline unsigned long __add_return_local_generic(volatile void *ptr,
> > +               unsigned long value, int size)
>
> size_t for size ?

No. It can be anything.

> > +extern unsigned long wrong_size_add_local(volatile void *ptr);
> > ...
> > +       /*
> > +        * Sanity checking, compile-time.
> > +        */
> > +       if (size == 8 && sizeof(unsigned long) != 8)
> > +               wrong_size_add_local(ptr);
> > ...
> > +       default:
> > +               wrong_size_add_local(ptr);
> > +       }
>
> should be BUILD_BUG_ON() ?

Does not work there.