Review request (M): 7085906: Replace the permgen allocated sentinelRef with a self-looped end

[Stefan Karlsson]

http://cr.openjdk.java.net/~stefank/7085906/webrev/

7085906: Replace the permgen allocated sentinelRef with a self-looped end

The reference processor uses the sentinelRef to mark the end of the 
lists of discovered References. All the collectors rely on the 
sentinelRef being allocated in the permgen, hence not moving. So, when 
permgen is removed this will not work.

We could probably make changes to the collectors to update all pointers 
to the sentinelRef, but the proposed solution is to remove the 
sentinelRef, and instead let the last Reference in a discovered chain 
point back to itself. Just like we do with the next field.

StefanK