So I think this phase is presently an expensive nop, and should be deleted entirely, along with supporting infrastructure such as DiscoveredListIterator::make_active(), which I think is only used here.
- is blocked by
- 
                    JDK-8269596 Snapshot soft ref policy before marking/copying -           
- Resolved
 
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- relates to
- 
                    JDK-6990442 (ref) Regression to clearing of a softly reachable object -           
- Open
 
-         
- 
                    JDK-6990438 (ref) Soft reference could consider strong if GC decides not to clear -           
- Open
 
-         
- 
                    JDK-8031401 Remove unused code in the reference processor -           
- Resolved
 
-         
- 
                    JDK-8202845 Refactor reference processing for improved parallelism -           
- Resolved
 
-         
- 
                    JDK-8270282 Semantically rename reference processing subphases -           
- Resolved
 
-         
- 
                    JDK-8046124 JEP 134: Intuitive Semantics for Nested Reference Objects -           
- Candidate
 
-         
- 
                    JDK-8043575 Dynamically parallelize reference processing work -           
- Resolved
 
-         
 
        