Re: [PATCH] Profile likely/unlikely macros

[Nick Piggin]

Andrew Morton wrote:
> 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().

I guess it is so it can be used in NMIs and interrupts without turning
interrupts off (so is somewhat lightweight).

But please Daniel, just use spinlocks and trylock. This is buggy because
it doesn't get the required release consistency correct.

--
SUSE Labs, Novell Inc.
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