Re: [PATCH 1/2] jump_labels: Add API to deal with keys embedded in structures

[Peter Zijlstra]

On Mon, Sep 19, 2016 at 06:21:27PM +0100, Marc Zyngier wrote:
> It is desirable to allow static keys to be integrated in structures,
> as it can lead do slightly more readable code. But the current API
> only provides DEFINE_STATIC_KEY_TRUE/FALSE, which is not exactly
> nice and leads to the following idiom:
> 
> 	static struct {
> 		int			foo;
> 		struct static_key_false	key;
> 	} bar = {
> 		.key	= STATIC_KEY_FALSE_INIT,
> 	};
> 
> 	[...]
> 
> 	if (static_branch_unlikely(&bar.key))
> 		foo = -1;
> 
> which doesn't follow the recommended API, and uses the internals
> of the static key implementation.
> 
> This patch introduces DECLARE_STATIC_KEY_TRUE/FALSE, as well as
> INIT_STATIC_KEY_TRUE/FALSE, which abstract such construct and
> allow the internals to evolve without having to fix everything else:
> 
> 	static struct {
> 		int			 foo;
> 		DECLARE_STATIC_KEY_FALSE(key);
> 	} bar = {
> 		INIT_STATIC_KEY_FALSE(.key),
> 	};

Hurm..

I think I like the first better, it looks more like actual C. Either way
around you need to now manually match up the type and initializer.