File : s-tpoben.ads
-- GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS --
-- SYSTEM.TASKING.PROTECTED_OBJECTS.ENTRIES --
-- S p e c --
-- $Revision: 1.13 $
-- Copyright (C) 1992-2001, 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 2, or (at your option) any later ver- --
-- sion. GNARL 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. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNARL; see file COPYING. If not, write --
-- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
-- MA 02111-1307, USA. --
-- As a special exception, if other files instantiate generics from this --
-- unit, or you link this unit with other files to produce an executable, --
-- this unit does not by itself cause the resulting executable to be --
-- covered by the GNU General Public License. This exception does not --
-- however invalidate any other reasons why the executable file might be --
-- covered by the GNU Public License. --
-- GNARL was developed by the GNARL team at Florida State University. It is --
-- now maintained by Ada Core Technologies Inc. in cooperation with Florida --
-- State University (http://www.gnat.com). --
-- This package contains all the simple primitives related to
-- Protected_Objects with entries (i.e init, lock, unlock).
-- The handling of protected objects with no entries is done in
-- System.Tasking.Protected_Objects, the complex routines for protected
-- objects with entries in System.Tasking.Protected_Objects.Operations.
-- The split between Entries and Operations is needed to break circular
-- dependencies inside the run time.
-- Note: the compiler generates direct calls to this interface, via Rtsfind.
-- Any changes to this interface may require corresponding compiler changes.
-- used for Limited_Controlled
package System.Tasking.Protected_Objects.Entries is
subtype Positive_Protected_Entry_Index is
Protected_Entry_Index range 1 .. Protected_Entry_Index'Last;
type Find_Body_Index_Access is access
(O : System.Address;
E : Protected_Entry_Index)
type Protected_Entry_Body_Array is
array (Positive_Protected_Entry_Index range <>) of Entry_Body;
-- This is an array of the executable code for all entry bodies of
-- a protected type.
type Protected_Entry_Body_Access is access all Protected_Entry_Body_Array;
type Protected_Entry_Queue_Array is
array (Protected_Entry_Index range <>) of Entry_Queue;
-- This type contains the GNARL state of a protected object. The
-- application-defined portion of the state (i.e. private objects)
-- is maintained by the compiler-generated code.
-- note that there is a simplified version of this type declared in
-- System.Tasking.PO_Simple that handle the simple case (no entries).
type Protection_Entries (Num_Entries : Protected_Entry_Index) is new
L : aliased Task_Primitives.Lock;
-- The underlying lock associated with a Protection_Entries.
-- Note that you should never (un)lock Object.L directly, but instead
-- use Lock_Entries/Unlock_Entries.
Compiler_Info : System.Address;
Call_In_Progress : Entry_Call_Link;
Ceiling : System.Any_Priority;
Old_Base_Priority : System.Any_Priority;
Pending_Action : Boolean;
-- Flag indicating that priority has been dipped temporarily
-- in order to avoid violating the priority ceiling of the lock
-- associated with this protected object, in Lock_Server.
-- The flag tells Unlock_Server or Unlock_And_Update_Server to
-- restore the old priority to Old_Base_Priority. This is needed
-- because of situations (bad language design?) where one
-- needs to lock a PO but to do so would violate the priority
-- ceiling. For example, this can happen when an entry call
-- has been requeued to a lower-priority object, and the caller
-- then tries to cancel the call while its own priority is higher
-- than the ceiling of the new PO.
Finalized : Boolean := False;
-- Set to True by Finalize to make this routine idempotent.
Entry_Bodies : Protected_Entry_Body_Access;
-- The following function maps the entry index in a call (which denotes
-- the queue to the proper entry) into the body of the entry.
Find_Body_Index : Find_Body_Index_Access;
Entry_Queues : Protected_Entry_Queue_Array (1 .. Num_Entries);
pragma Volatile (Protection_Entries);
-- No default initial values for this type, since call records
-- will need to be re-initialized before every use.
type Protection_Entries_Access is access all Protection_Entries'Class;
-- See comments in s-tassta.adb about the implicit call to Current_Master
-- generated by this declaration.
function To_Protection_Entries is new Unchecked_Conversion
function To_Address is
new Unchecked_Conversion (Protection_Entries_Access, System.Address);
function To_Protection is
new Unchecked_Conversion (System.Address, Protection_Entries_Access);
(Object : Protection_Entries_Access) return Boolean;
-- Returns True if an Interrupt_Handler or Attach_Handler pragma applies
-- to the protected object. That is to say this primitive returns False for
-- Protection, but is overriden to return True when interrupt handlers are
-- declared so the check required by C.3.1(11) can be implemented in
(Object : Protection_Entries_Access;
Ceiling_Priority : Integer;
Compiler_Info : System.Address;
Entry_Bodies : Protected_Entry_Body_Access;
Find_Body_Index : Find_Body_Index_Access);
-- Initialize the Object parameter so that it can be used by the runtime
-- to keep track of the runtime state of a protected object.
procedure Lock_Entries (Object : Protection_Entries_Access);
-- Lock a protected object for write access. Upon return, the caller
-- owns the lock to this object, and no other call to Lock or
-- Lock_Read_Only with the same argument will return until the
-- corresponding call to Unlock has been made by the caller.
-- Program_Error is raised in case of ceiling violation.
(Object : Protection_Entries_Access; Ceiling_Violation : out Boolean);
-- Same as above, but return the ceiling violation status instead of
-- raising Program_Error.
procedure Lock_Read_Only_Entries (Object : Protection_Entries_Access);
-- Lock a protected object for read access. Upon return, the caller
-- owns the lock for read access, and no other calls to Lock with the
-- same argument will return until the corresponding call to Unlock
-- has been made by the caller. Other calls to Lock_Read_Only may (but
-- need not) return before the call to Unlock, and the corresponding
-- callers will also own the lock for read access.
-- Note: we are not currently using this interface, it is provided
-- for possible future use. At the current time, everyone uses Lock
-- for both read and write locks.
procedure Unlock_Entries (Object : Protection_Entries_Access);
-- Relinquish ownership of the lock for the object represented by
-- the Object parameter. If this ownership was for write access, or
-- if it was for read access where there are no other read access
-- locks outstanding, one (or more, in the case of Lock_Read_Only)
-- of the tasks waiting on this lock (if any) will be given the
-- lock and allowed to return from the Lock or Lock_Read_Only call.
procedure Finalize (Object : in out Protection_Entries);
-- Clean up a Protection object; in particular, finalize the associated
-- Lock object.