-------------------------------------------------------------------------------
-- Mutual exclusion protocol 3b_p2
-- (3 bits, simple conditions, deadlock-free)
-- generated automatically in [Bar-David-Taubenfeld-03]
-------------------------------------------------------------------------------

module mutex_3b_p2 (ARCH_3B) is

!nat_bits 2 -- use 2 bits to store natural numbers

(*
 * Process P (i) competing for the access to critical section
 * where i = 0..1, j = 1 - i
 *
 *   loop
 *      non critical section ;
 *      A[i] := 1 ;
 *      while B != A[j] do
 *         while A[B] = i do
 *            B := A[0]
 *         end while
 *      end while ;
 *      critical section ;
 *      A[i] := 0
 *   end loop
 *)

process P [NCS:Pid, CS:Access, A, B:Operation] (i: Pid) is
   var j: Pid, a_0, a_j, a_b, b:Nat in
   j := 1 - i;
   loop
      NCS (i);
      A (Write, i, 1 of Nat, i);
      loop L1 in
         B (Read, ?b, i);
         A (Read, j, ?a_j, i);
         if b == a_j then break L1 end if;
         loop L2 in
            B (Read, ?b, i);
            A (Read, b of Pid, ?a_b, i);
            if a_b != i then break L2 end if;
            A (Read, 0 of Pid, ?a_0, i);
            B (Write, a_0, i)
         end loop
      end loop;
      CS (Enter, i); CS (Leave, i);
      A (Write, i, 0 of Nat, i)
   end loop
   end var
end process

-------------------------------------------------------------------------------

process Main [NCS:Pid, CS:Access, A, B:Operation, MU:Latency] is
   Arch_3b [NCS, CS, A, B, MU]
end process

end module