Re: [PATCH 3/4] relayfs for 2.6.10: locking/lockless implementation

[Greg KH <greg@kroah.com>]

On Thu, Jan 13, 2005 at 10:04:33PM -0500, Karim Yaghmour wrote:
> +/**
> + *	compare_and_store_volatile - self-explicit
> + *	@ptr: ptr to the word that will receive the new value
> + *	@oval: the value we think is currently in *ptr
> + *	@nval: the value *ptr will get if we were right
> + */
> +inline int
> +compare_and_store_volatile(volatile u32 *ptr,
> +			   u32 oval,
> +			   u32 nval)
> +{
> +	u32 prev;
> +
> +	barrier();
> +	prev = cmpxchg(ptr, oval, nval);
> +	barrier();
> +
> +	return (prev == oval);
> +}

Why is this function needed?  What's wrong with the "normal" cmpxchg?

> +/**
> + *	atomic_set_volatile - atomically set the value in ptr to nval.
> + *	@ptr: ptr to the word that will receive the new value
> + *	@nval: the new value
> + */
> +inline void
> +atomic_set_volatile(atomic_t *ptr,
> +		    u32 nval)
> +{
> +	barrier();
> +	atomic_set(ptr, (int)nval);
> +	barrier();
> +}

Same here, what's wrong with the normal atomic_set()?

Same question also goes for the other functions like this in this file.

thanks,

greg k-h