Re: [PATCH] updated low-latency zap_page_range

[Andrew Morton]

Robert Love wrote:
> 
> ...
> +static inline void cond_resched_lock(spinlock_t * lock)
> +{
> +       if (need_resched() && preempt_count() == 1) {
> +               _raw_spin_unlock(lock);
> +               preempt_enable_no_resched();
> +               __cond_resched();
> +               spin_lock(lock);
> +       }
> +}

Maybe I'm being thick.  How come a simple spin_unlock() in here
won't do the right thing?

And this won't _really_ compile to nothing with CONFIG_PREEMPT=n,
will it?  It just does nothing because preempt_count() is zero?

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