And if so, how in the hell do you play some of the faster riffs? My finger kinda locks, and screws up my playing if I'm playing over too many frets.

All of my fingers are double-jointed. Yes, it sucks bad.

That sucks

What does it mean to be double jointed anyway? And why is it bad?
My fingers have three joints. Does it mean that your fingers have only two?

It means the joint can bend the opposite direction partway. When playing guitar, certain movements will cause your finger to lock in that position for a brief moment. And when I play bar chords, you can actually see the first joint after my knuckle bend backward part way... at least when I'm playing my acoustic guitar.

I'd assume this is the same problem others have.
The question was whether there was an exercise of some nature to correct it or better it somehow.

Ugh, yes. I don't have problems with any other fingers, but when stretching, my pinky's last knuckle pops inward and gets stuck. I hate it.

Wierd..

Same happens to me, the best thing to do is either stretch it a lot so it doesn't lock up as much, or (if your pinky is long enough) keep it at a curve, and don't let it straighten out.