static keys: Introduce 'struct static_key',static_key_true()/false() and static_key_slow_[inc|dec]()

[Ingo Molnar]

* Ingo Molnar <mingo@xxxxxxx> wrote:

> * Ingo Molnar <mingo@xxxxxxx> wrote:
> 
> > So, a modified scheme would be:
> > 
> >         #include <linux/static_key.h>
> > 
> >         struct static_key key = STATIC_KEY_INIT_TRUE;
> > 
> >         if (static_key_false(&key))
> >                 do unlikely code
> >         else
> >                 do likely code
> > 
> > Or:
> > 
> >         if (static_key_true(&key))
> >                 do likely code
> >         else
> >                 do unlikely code
> > 
> > The static key is modified via:
> > 
> >         static_key_slow_inc(&key);
> >         ...
> >         static_key_slow_dec(&key);
> > 
> > Is that API fine? I'll rework the series to such an effect if 
> > everyone agrees.
> 
> I.e. something like the patch below on top of 
> tip:perf/jump-labels.
> 
> Untested - will test it and will refactor the series if 
> everyone's happy.

So, below is the second version of my 'struct static_key' patch, 
with the confusing very_likely()/very_unlikely() method renamed 
to static_key_true()/static_key_false().

Thanks,

	Ingo

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