Re: [Xen-devel] [PATCHv4 1/8] x86: provide arch_fetch_and_add()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 30.04.15 at 17:33, <david.vrabel@xxxxxxxxxx> wrote:
> +static always_inline unsigned long __xadd(
> +    volatile void *ptr, unsigned long v, int size)
> +{
> +    switch ( size )
> +    {
> +    case 1:
> +        asm volatile ( "lock; xaddb %b0,%1"
> +                       : "+r" (v), "+m" (*__xg((volatile void *)ptr))

"ptr" already is "volatile void *", so why the cast? Or is this just
an artifact of __xchg() doing the same odd thing?

> +#define arch_fetch_and_add(ptr, v) \
> +    ({ \
> +        (typeof(*(ptr)))__xadd(ptr, (typeof(*(ptr)))(v), sizeof(*(ptr))); \
> +    })

It being a single expression inside the braces I don't think you really
need the ({}) GNU extension here.

Both of course easily adjusted while committing, if you agree.

Jan


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