Circular dependency detection

[host6]

unTill depends on UBL and Db, UBL depends on Db, Db depends on UBL

• unTill
  • UBL
    • Db
      • UBL
        ...
  • Db
    • UBL
      ....

Deadlock: Db waits for UBL,UBL waits for Db

• unTill gets its dependencies: UBL and Db
• UBL and DB are computing simultaneously
  • UBL
    • put UBL-DUMMY into cache (2)
    • compute its dependency: Db
      • Db sees that cache contains Db-DUMMY (1) and waits for it
  • Db
    • put Db-DUMMY into cache (1)
    • compute its dependency: UBL
      • UBL sees that cache contains UBL-DUMMY (2) and waits for it

[host6]

In case if there is only one branch (unTIll depends only on UBL or only on Db) then circular dependency is detected well, no problems