------------------------------------------------------------------------------ -- -- -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS -- -- -- -- SYSTEM.TASKING.PROTECTED_OBJECTS.SINGLE_ENTRY -- -- -- -- B o d y -- -- -- -- Copyright (C) 1998-2018, Free Software Foundation, Inc. -- -- -- -- GNARL is free software; you can redistribute it and/or modify it under -- -- terms of the GNU General Public License as published by the Free Soft- -- -- ware Foundation; either version 3, or (at your option) any later ver- -- -- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- -- or FITNESS FOR A PARTICULAR PURPOSE. -- -- -- -- As a special exception under Section 7 of GPL version 3, you are granted -- -- additional permissions described in the GCC Runtime Library Exception, -- -- version 3.1, as published by the Free Software Foundation. -- -- -- -- You should have received a copy of the GNU General Public License and -- -- a copy of the GCC Runtime Library Exception along with this program; -- -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- -- . -- -- -- -- GNARL was developed by the GNARL team at Florida State University. -- -- Extensive contributions were provided by Ada Core Technologies, Inc. -- -- -- ------------------------------------------------------------------------------ pragma Style_Checks (All_Checks); -- Turn off subprogram ordering check, since restricted GNARLI subprograms are -- gathered together at end. -- This package provides an optimized version of Protected_Objects.Operations -- and Protected_Objects.Entries making the following assumptions: -- PO has only one entry -- There is only one caller at a time (No_Entry_Queue) -- There is no dynamic priority support (No_Dynamic_Priorities) -- No Abort Statements -- (No_Abort_Statements, Max_Asynchronous_Select_Nesting => 0) -- PO are at library level -- No Requeue -- None of the tasks will terminate (no need for finalization) -- This interface is intended to be used in the ravenscar and restricted -- profiles, the compiler is responsible for ensuring that the conditions -- mentioned above are respected, except for the No_Entry_Queue restriction -- that is checked dynamically in this package, since the check cannot be -- performed at compile time, and is relatively cheap (see PO_Do_Or_Queue, -- Service_Entry). pragma Polling (Off); -- Turn off polling, we do not want polling to take place during tasking -- operations. It can cause infinite loops and other problems. pragma Suppress (All_Checks); -- Why is this required ??? with Ada.Exceptions; with System.Task_Primitives.Operations; with System.Parameters; package body System.Tasking.Protected_Objects.Single_Entry is package STPO renames System.Task_Primitives.Operations; use Parameters; ----------------------- -- Local Subprograms -- ----------------------- procedure Send_Program_Error (Entry_Call : Entry_Call_Link); pragma Inline (Send_Program_Error); -- Raise Program_Error in the caller of the specified entry call -------------------------- -- Entry Calls Handling -- -------------------------- procedure Wakeup_Entry_Caller (Entry_Call : Entry_Call_Link); pragma Inline (Wakeup_Entry_Caller); -- This is called at the end of service of an entry call, to abort the -- caller if he is in an abortable part, and to wake up the caller if he -- is on Entry_Caller_Sleep. Call it holding the lock of Entry_Call.Self. procedure Wait_For_Completion (Entry_Call : Entry_Call_Link); pragma Inline (Wait_For_Completion); -- This procedure suspends the calling task until the specified entry call -- has either been completed or cancelled. On exit, the call will not be -- queued. This waits for calls on protected entries. -- Call this only when holding Self_ID locked. procedure Check_Exception (Self_ID : Task_Id; Entry_Call : Entry_Call_Link); pragma Inline (Check_Exception); -- Raise any pending exception from the Entry_Call. This should be called -- at the end of every compiler interface procedure that implements an -- entry call. The caller should not be holding any locks, or there will -- be deadlock. procedure PO_Do_Or_Queue (Object : Protection_Entry_Access; Entry_Call : Entry_Call_Link); -- This procedure executes or queues an entry call, depending on the status -- of the corresponding barrier. The specified object is assumed locked. --------------------- -- Check_Exception -- --------------------- procedure Check_Exception (Self_ID : Task_Id; Entry_Call : Entry_Call_Link) is pragma Warnings (Off, Self_ID); procedure Internal_Raise (X : Ada.Exceptions.Exception_Id); pragma Import (C, Internal_Raise, "__gnat_raise_with_msg"); use type Ada.Exceptions.Exception_Id; E : constant Ada.Exceptions.Exception_Id := Entry_Call.Exception_To_Raise; begin if E /= Ada.Exceptions.Null_Id then Internal_Raise (E); end if; end Check_Exception; ------------------------ -- Send_Program_Error -- ------------------------ procedure Send_Program_Error (Entry_Call : Entry_Call_Link) is Caller : constant Task_Id := Entry_Call.Self; begin Entry_Call.Exception_To_Raise := Program_Error'Identity; if Single_Lock then STPO.Lock_RTS; end if; STPO.Write_Lock (Caller); Wakeup_Entry_Caller (Entry_Call); STPO.Unlock (Caller); if Single_Lock then STPO.Unlock_RTS; end if; end Send_Program_Error; ------------------------- -- Wait_For_Completion -- ------------------------- procedure Wait_For_Completion (Entry_Call : Entry_Call_Link) is Self_Id : constant Task_Id := Entry_Call.Self; begin Self_Id.Common.State := Entry_Caller_Sleep; STPO.Sleep (Self_Id, Entry_Caller_Sleep); Self_Id.Common.State := Runnable; end Wait_For_Completion; ------------------------- -- Wakeup_Entry_Caller -- ------------------------- -- This is called at the end of service of an entry call, to abort the -- caller if he is in an abortable part, and to wake up the caller if it -- is on Entry_Caller_Sleep. It assumes that the call is already off-queue. -- (This enforces the rule that a task must be off-queue if its state is -- Done or Cancelled.) Call it holding the lock of Entry_Call.Self. -- The caller is waiting on Entry_Caller_Sleep, in Wait_For_Completion. procedure Wakeup_Entry_Caller (Entry_Call : Entry_Call_Link) is Caller : constant Task_Id := Entry_Call.Self; begin pragma Assert (Caller.Common.State /= Terminated and then Caller.Common.State /= Unactivated); Entry_Call.State := Done; STPO.Wakeup (Caller, Entry_Caller_Sleep); end Wakeup_Entry_Caller; ----------------------- -- Restricted GNARLI -- ----------------------- -------------------------------------------- -- Exceptional_Complete_Single_Entry_Body -- -------------------------------------------- procedure Exceptional_Complete_Single_Entry_Body (Object : Protection_Entry_Access; Ex : Ada.Exceptions.Exception_Id) is begin Object.Call_In_Progress.Exception_To_Raise := Ex; end Exceptional_Complete_Single_Entry_Body; --------------------------------- -- Initialize_Protection_Entry -- --------------------------------- procedure Initialize_Protection_Entry (Object : Protection_Entry_Access; Ceiling_Priority : Integer; Compiler_Info : System.Address; Entry_Body : Entry_Body_Access) is begin Initialize_Protection (Object.Common'Access, Ceiling_Priority); Object.Compiler_Info := Compiler_Info; Object.Call_In_Progress := null; Object.Entry_Body := Entry_Body; Object.Entry_Queue := null; end Initialize_Protection_Entry; ---------------- -- Lock_Entry -- ---------------- -- Compiler interface only -- Do not call this procedure from within the run-time system. procedure Lock_Entry (Object : Protection_Entry_Access) is begin Lock (Object.Common'Access); end Lock_Entry; -------------------------- -- Lock_Read_Only_Entry -- -------------------------- -- Compiler interface only -- Do not call this procedure from within the runtime system procedure Lock_Read_Only_Entry (Object : Protection_Entry_Access) is begin Lock_Read_Only (Object.Common'Access); end Lock_Read_Only_Entry; -------------------- -- PO_Do_Or_Queue -- -------------------- procedure PO_Do_Or_Queue (Object : Protection_Entry_Access; Entry_Call : Entry_Call_Link) is Barrier_Value : Boolean; begin -- When the Action procedure for an entry body returns, it must be -- completed (having called [Exceptional_]Complete_Entry_Body). Barrier_Value := Object.Entry_Body.Barrier (Object.Compiler_Info, 1); if Barrier_Value then if Object.Call_In_Progress /= null then -- This violates the No_Entry_Queue restriction, send -- Program_Error to the caller. Send_Program_Error (Entry_Call); return; end if; Object.Call_In_Progress := Entry_Call; Object.Entry_Body.Action (Object.Compiler_Info, Entry_Call.Uninterpreted_Data, 1); Object.Call_In_Progress := null; if Single_Lock then STPO.Lock_RTS; end if; STPO.Write_Lock (Entry_Call.Self); Wakeup_Entry_Caller (Entry_Call); STPO.Unlock (Entry_Call.Self); if Single_Lock then STPO.Unlock_RTS; end if; else pragma Assert (Entry_Call.Mode = Simple_Call); if Object.Entry_Queue /= null then -- This violates the No_Entry_Queue restriction, send -- Program_Error to the caller. Send_Program_Error (Entry_Call); return; else Object.Entry_Queue := Entry_Call; end if; end if; exception when others => Send_Program_Error (Entry_Call); end PO_Do_Or_Queue; ---------------------------- -- Protected_Single_Count -- ---------------------------- function Protected_Count_Entry (Object : Protection_Entry) return Natural is begin if Object.Entry_Queue /= null then return 1; else return 0; end if; end Protected_Count_Entry; --------------------------------- -- Protected_Single_Entry_Call -- --------------------------------- procedure Protected_Single_Entry_Call (Object : Protection_Entry_Access; Uninterpreted_Data : System.Address) is Self_Id : constant Task_Id := STPO.Self; Entry_Call : Entry_Call_Record renames Self_Id.Entry_Calls (1); begin -- If pragma Detect_Blocking is active then Program_Error must be -- raised if this potentially blocking operation is called from a -- protected action. if Detect_Blocking and then Self_Id.Common.Protected_Action_Nesting > 0 then raise Program_Error with "potentially blocking operation"; end if; Lock_Entry (Object); Entry_Call.Mode := Simple_Call; Entry_Call.State := Now_Abortable; Entry_Call.Uninterpreted_Data := Uninterpreted_Data; Entry_Call.Exception_To_Raise := Ada.Exceptions.Null_Id; PO_Do_Or_Queue (Object, Entry_Call'Access); Unlock_Entry (Object); -- The call is either `Done' or not. It cannot be cancelled since there -- is no ATC construct. pragma Assert (Entry_Call.State /= Cancelled); if Entry_Call.State /= Done then if Single_Lock then STPO.Lock_RTS; end if; STPO.Write_Lock (Self_Id); Wait_For_Completion (Entry_Call'Access); STPO.Unlock (Self_Id); if Single_Lock then STPO.Unlock_RTS; end if; end if; Check_Exception (Self_Id, Entry_Call'Access); end Protected_Single_Entry_Call; ----------------------------------- -- Protected_Single_Entry_Caller -- ----------------------------------- function Protected_Single_Entry_Caller (Object : Protection_Entry) return Task_Id is begin return Object.Call_In_Progress.Self; end Protected_Single_Entry_Caller; ------------------- -- Service_Entry -- ------------------- procedure Service_Entry (Object : Protection_Entry_Access) is Entry_Call : constant Entry_Call_Link := Object.Entry_Queue; Caller : Task_Id; begin if Entry_Call /= null and then Object.Entry_Body.Barrier (Object.Compiler_Info, 1) then Object.Entry_Queue := null; if Object.Call_In_Progress /= null then -- Violation of No_Entry_Queue restriction, raise exception Send_Program_Error (Entry_Call); Unlock_Entry (Object); return; end if; Object.Call_In_Progress := Entry_Call; Object.Entry_Body.Action (Object.Compiler_Info, Entry_Call.Uninterpreted_Data, 1); Object.Call_In_Progress := null; Caller := Entry_Call.Self; Unlock_Entry (Object); if Single_Lock then STPO.Lock_RTS; end if; STPO.Write_Lock (Caller); Wakeup_Entry_Caller (Entry_Call); STPO.Unlock (Caller); if Single_Lock then STPO.Unlock_RTS; end if; else -- Just unlock the entry Unlock_Entry (Object); end if; exception when others => Send_Program_Error (Entry_Call); Unlock_Entry (Object); end Service_Entry; ------------------ -- Unlock_Entry -- ------------------ procedure Unlock_Entry (Object : Protection_Entry_Access) is begin Unlock (Object.Common'Access); end Unlock_Entry; end System.Tasking.Protected_Objects.Single_Entry;