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------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
-- --
-- S Y S T E M . T A S K I N G . P R O T E C T E D _ O B J E C T S . --
-- E N T R I E S --
-- --
-- S p e c --
-- --
-- Copyright (C) 1992-2005, 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. --
-- Extensive contributions were provided by Ada Core Technologies, Inc. --
-- --
------------------------------------------------------------------------------
-- 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.
with Ada.Finalization;
-- used for Limited_Controlled
with Unchecked_Conversion;
package System.Tasking.Protected_Objects.Entries is
pragma Elaborate_Body;
subtype Positive_Protected_Entry_Index is
Protected_Entry_Index range 1 .. Protected_Entry_Index'Last;
type Find_Body_Index_Access is access
function
(O : System.Address;
E : Protected_Entry_Index)
return 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
Ada.Finalization.Limited_Controlled
with record
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;
-- Pointer to compiler-generated record representing protected object
Call_In_Progress : Entry_Call_Link;
-- Pointer to the entry call being executed (if any)
Ceiling : System.Any_Priority;
-- Ceiling priority associated with the protected object
Owner : Task_Id;
-- This field contains the protected object's owner. Null_Task
-- indicates that the protected object is not currently being used.
-- This information is used for detecting the type of potentially
-- blocking operations described in the ARM 9.5.1, par. 15 (external
-- calls on a protected subprogram with the same target object as that
-- of the protected action).
Old_Base_Priority : System.Any_Priority;
-- Task's base priority when the protected operation was called
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;
-- Pointer to an array containing the executable code for all entry
-- bodies of a protected type.
-- 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);
end record;
-- 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_Address is
new Unchecked_Conversion (Protection_Entries_Access, System.Address);
function To_Protection is
new Unchecked_Conversion (System.Address, Protection_Entries_Access);
function Has_Interrupt_Or_Attach_Handler
(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
-- System.Tasking.Protected_Objects.Initialize_Protection.
procedure Initialize_Protection_Entries
(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.
procedure Lock_Entries
(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.
private
procedure Finalize (Object : in out Protection_Entries);
-- Clean up a Protection object; in particular, finalize the associated
-- Lock object.
end System.Tasking.Protected_Objects.Entries;
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