8005697: Add StampedLock - JEP 155

[Aleksey Shipilev]

On 01/28/2013 03:32 PM, Chris Hegarty wrote:
> StampedLock, as usual, is coming from Doug Lea, with assistance from
> members of the former JCP JSR-166 Expert Group. Aleksey Shipilev, Dave
> Dice, and I, have all informally reviewed this, and our feedback is
> already incorporated in this version.

I want to dub my informal OK here (not a Reviewer by OpenJDK census). We
will follow up with the extensive functional and performance testing
once this basic version lands in JDK8.

-Aleksey.

N.B.: This class marks the first usage of Unsafe.*fence() intrinsics
Doug et al. added in HS last year, replacing the weird
Unsafe.putVolatileLong hacks from the strange world before.