Re: [PATCH v2 1/2] spinlock: New spinlock_refcount.h for locklessupdate of refcount

[Linus Torvalds]

On Sat, Jun 29, 2013 at 2:58 PM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> STEP 1:
>
>  - create a new set of config option (say
> "CONFIG_[ARCH_]SPINLOCK_REFCOUNT") that defaults to 'y' and isn't
> actually asked about anywhere.

That "defauls to 'y'" was incomplete/misleading. The
ARCH_SPINLOCK_REFCOUNT config option should default to 'n' (the
example code snippet did that correctly: a bool config option defaults
to 'n' unless stated otherwise).

The SPINLOCK_REFCOUNT in turn _should_ have a "default y" (the sample
snippet I posted didn't have that), but that 'y' is then obviously
normally disabled by the "depends on" logic, so it only takes effect
when ARCH_SPINLOCK_REFCOUNT is set, and none of the spinlock debug
things are enabled.

I hope that was all fairly obvious from the concept (and the real
examples of us already doing things like this with the whole
CONFIG_GENERIC_STRNLEN_USER and CONFIG_DCACHE_WORD_ACCESS examples),
but I thought I'd follow up with an explicit correction, since both
the explanation and sample snippets were somewhat misleading.

                Linus
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