Re: [PATCH] Profile likely/unlikely macros

[Andrew Morton]

Daniel Walker <dwalker@xxxxxxxxxx> wrote:
>
>  +	if (likeliness->type & LIKELY_UNSEEN) {
>  +		if (atomic_dec_and_test(&likely_lock)) {
>  +			if (likeliness->type & LIKELY_UNSEEN) {
>  +				likeliness->type &= (~LIKELY_UNSEEN);
>  +				likeliness->next = likeliness_head;
>  +				likeliness_head = likeliness;
>  +			}
>  +		}
>  +		atomic_inc(&likely_lock);

hm, good enough I guess.  It does need a comment explaining why we
don't just do spin_lock().

It'd be a bit saner to do

	if (!test_and_set_bit(&foo, 0)) {
		...
		clear_bit(&foo, 0);
	}

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