Was the Mishkan Functional in Shaul's Time?

When David, fleeing the suspicious Shaul, comes to the Cohanim (Priests) of the Mishkan (tabernacle) at Kiryat Yearim, they offer him some of the Lechem Hapanim (Temple Bread,) which is forbidden to David, a non-Cohen, in Halachah (Jewish Law.)  One explanation is that David was starving and was fed only to save his life, permissible in Halachah.  However, I find this interpretation a bit difficult as he had been travelling a great deal already, seemingly without trouble, and because he took enough to last many days, which would seem to be going beyond the bare necessities of survival permitted by Halachah.  Another possible explanation is that the Mishkan at Kiryat Yearim was not fully functional so soon after the destruction of the Mishkan in Shiloh by the Phillistines, so the bread did not yet have the status of actual Lechem Papanim and exception could be made.