question: @ Nullable public GridCacheMvccCandidate addEntry ( GridDhtCacheEntry entry ) throws GridCacheEntryRemovedException , GridDistributedLockCancelledException { if ( log . isDebugEnabled ( ) ) log . debug ( "Adding entry: " + entry ) ; if ( entry == null ) return null ; if ( timedOut ) return null ; GridCacheMvccCandidate c = entry . addDhtLocal ( nearNodeId , nearLockVer , topVer , threadId , lockVer , null , null , timeout , false , inTx ( ) , implicitSingle ( ) ) ; if ( c == null && timeout < 0 ) { if ( log . isDebugEnabled ( ) ) log . debug ( "Failed to acquire lock with negative timeout: " + entry ) ; onFailed ( false ) ; return null ; } synchronized ( sync ) { entries . add ( c == null || c . reentry ( ) ? null : entry ) ; if ( c != null && ! c . reentry ( ) ) pendingLocks . add ( entry . key ( ) ) ; } if ( timedOut ) { entry . removeLock ( lockVer ) ; return null ; } return c ; }
target:  Adds entry to future.