code: public synchronized Lease record(@Nonnull FilePath p) {
          if (LOGGER.isLoggable(Level.FINE)) {
              LOGGER.log(Level.FINE, "recorded " + p, new Throwable("from " + this));
          }
          Entry old = inUse.put(p.getRemote(), new Entry(p, false));
          if (old!=null)
              throw new AssertionError("Tried to record a workspace already owned: "+old);
          return lease(p);
      }
docs: Just record that this workspace is being used, without paying any attention to the synchronization support.