On Tue, Sep 20, 2016 at 11:42:23AM +0200, Peter Zijlstra wrote:
> 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.
>
It may have been one of my review comments the prompted these patches,
because from reading Documentation/static-keys.txt, it seems that
referencing 'struct static_key' directly should be deprecated, and
instead developers should use the update API replacements.
I wonder if it's worth slightly updating the documentation then?
Thanks,
-Christoffer
