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423 | ------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
-- --
-- SYSTEM.TASKING.PROTECTED_OBJECTS.SINGLE_ENTRY --
-- --
-- B o d y --
-- --
-- Copyright (C) 1998-2023, 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 --
-- <http://www.gnu.org/licenses/>. --
-- --
-- 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 Suppress (All_Checks);
-- Why is this required ???
with Ada.Exceptions;
with System.Task_Primitives.Operations;
package body System.Tasking.Protected_Objects.Single_Entry is
package STPO renames System.Task_Primitives.Operations;
-----------------------
-- 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;
STPO.Write_Lock (Caller);
Wakeup_Entry_Caller (Entry_Call);
STPO.Unlock (Caller);
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;
STPO.Write_Lock (Entry_Call.Self);
Wakeup_Entry_Caller (Entry_Call);
STPO.Unlock (Entry_Call.Self);
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_Count_Entry --
---------------------------
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 (Self_Id.Entry_Calls'First);
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
STPO.Write_Lock (Self_Id);
Wait_For_Completion (Entry_Call'Access);
STPO.Unlock (Self_Id);
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);
STPO.Write_Lock (Caller);
Wakeup_Entry_Caller (Entry_Call);
STPO.Unlock (Caller);
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;
|