Re: [Xen-devel] [PATCH 1/2] asm/atomic.h: common prototyping (add xen/atomic.h)

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 13/07/16 12:23, Corneliu ZUZU wrote:
> Following Andrew Cooper's suggestion, create a common-side <xen/atomic.h> to
> establish, among others, prototypes of atomic functions called from 
> common-code.
> Done to avoid introducing inconsistencies between arch-side <asm/atomic.h>
> headers when we make subtle changes to one of them.
>
> Some arm-side macros had to be turned into inline functions in the process.
>
> Also includes a minor adjustment asm-x86/atomic.h: reorder 
> atomic_inc_and_test()
> to follow after atomic_inc().

Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>


> Signed-off-by: Corneliu ZUZU <czuzu@xxxxxxxxxxxxxxx>

Thanks for doing this!

> diff --git a/xen/include/xen/atomic.h b/xen/include/xen/atomic.h
> new file mode 100644
> index 0000000..5d5c051
> --- /dev/null
> +++ b/xen/include/xen/atomic.h
> @@ -0,0 +1,155 @@
> +/*
> + * include/xen/atomic.h
> + *
> + * Common atomic operations entities (atomic_t, function prototypes).
> + * Include _from_ arch-side <asm/atomic.h>.
> + *
> + * Copyright (c) 2016 Bitdefender S.R.L.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along 
> with
> + * this program; If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#ifndef __XEN_ATOMIC_H__
> +#define __XEN_ATOMIC_H__
> +
> +/*
> + * NB. I've pushed the volatile qualifier into the operations. This allows
> + * fast accessors such as _atomic_read() and _atomic_set() which don't give
> + * the compiler a fit.
> + */

I would recommend simply dropping this paragraph.  Is is very out of date.

> +typedef struct { int counter; } atomic_t;
> +
> +#define ATOMIC_INIT(i) { (i) }
> +
> +/**
> + * atomic_read - read atomic variable
> + * @v: pointer of type atomic_t
> + *
> + * Atomically reads the value of @v.
> + */
> +static inline int atomic_read(atomic_t *v);
> +
> +/**
> + * _atomic_read - read atomic variable non-atomically
> + * @v atomic_t
> + *
> + * Non-atomically reads the value of @v
> + */
> +static inline int _atomic_read(atomic_t v);
> +
> +/**
> + * atomic_set - set atomic variable
> + * @v: pointer of type atomic_t
> + * @i: required value
> + *
> + * Atomically sets the value of @v to @i.
> + */
> +static inline void atomic_set(atomic_t *v, int i);
> +
> +/**
> + * _atomic_set - set atomic variable non-atomically
> + * @v: pointer of type atomic_t
> + * @i: required value
> + *
> + * Non-atomically sets the value of @v to @i.
> + */
> +static inline void _atomic_set(atomic_t *v, int i);
> +

/**
 * atomic_cmpxchg - compare and exchange an atomic variable
 *...
 */

> +static inline int atomic_cmpxchg(atomic_t *v, int old, int new);

With those changes, Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

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