Thin Lock Implementation

[Bartosz Milewski]

Brad Roberts wrote:
> I'll agree that inbetween is relatively rare, but just because there's 
> contention, doesn't require the switch to heavy locks.  In a lot of the 
> code I have written, one spin (assuming the spin utilizes rep; nop;) is 
> sufficient for the 'blocked' acquire to finish it's acquire.  The use of 
> heavy weight locks in that scenario is a net loss.

A thin lock is not a spin lock. It's an optimization on top of the OS 
lock specifically for the no-contention case. If there is contention, 
the OS lock, which is part of FatLock, is used. It presumably does its 
own optimizations, so calling it "heavy weight" may be unfair.