Atomic Limit Counter Add and Subtract, and QQ about goto

[Leonardo Brás]

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