Atomic Limit Counter Add and Subtract, and QQ about goto

[Leonardo Brás <leobras.c@xxxxxxxxx>]

Hi Paul,

I was reading the Counting Chapter in detail, and the QQ about avoiding a Goto
got my attention:

Listing 5.13: Atomic Limit Counter Add and Subtract
Quick Quiz 5.43: Yecch! Why the ugly goto on line 11 of
Listing 5.13? Haven’t you heard of the break statement???

And I was thinking on an alternate solution to those, by calling slowpath as a
function in this simple change:

```
inline int add_count_slowpath(unsigned long delta)
{
	spin_lock(&gblcnt_mutex);
	globalize_count();

	if (globalcountmax - globalcount - globalreserve < delta) {
		flush_local_count();
		if (globalcountmax - globalcount - globalreserve < delta) {
			spin_unlock(&gblcnt_mutex);
			return 0;
		}
	}

	globalcount += delta;
	balance_count();
	spin_unlock(&gblcnt_mutex);
	return 1;
}


int add_count(unsigned long delta)
{
	int c;
	int cm;
	int old;
	int new;

	do {
		split_counterandmax(&counterandmax, &old, &c, &cm);
		if (delta > MAX_COUNTERMAX || c + delta > cm)
			return add_count_slowpath(delta);
		new = merge_counterandmax(c + delta, cm);	
	 while (atomic_cmpxchg(&counterandmax, old, new) != old);

	return 1;

}
```

Does it make sense?
Does it introduce any overhead I couldn't see?

Thanks!
Leo