Re: [PATCH v7 1/4] spinlock: A new lockref structure for locklessupdate of refcount

[Benjamin Herrenschmidt]

On Fri, 2013-08-30 at 12:06 +1000, Michael Neuling wrote:

> powerpc patch below. I'm using arch_spin_is_locked() to implement
> arch_spin_value_unlocked().

>  
> +static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
> +{
> +	return !arch_spin_is_locked(&lock);
> +}
> +

Arguably, it should be done the other way around :-) 

arch_spin_value_unlocked semantics is to basically operate on an already
read copy of the value, while arch_spin_is_locked() has ACCESS_ONE
semantics on *top* of that.

Or we can keep both completely separate like Linus does on x86.

Cheers,
Ben.


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