On 06/29/2013 06:47 PM, Linus Torvalds wrote:
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
Thank for the clarification, but I had already understood the
implication of your suggestion. Each architecture has to explicitly
opt-in by defining an ARCH_SPINLOCK_REFCOUNT in its Kconfig file to have
this lockref feature enabled. In this way, each architecture can take
its time to verify it works before enabling it. My patch will enable
enable the x86 as I don't have test machines for the other architectures.
Regards,
Longman
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