243 lines
10 KiB
Ada
243 lines
10 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
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-- --
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-- 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 --
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 1992-2011, Free Software Foundation, Inc. --
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-- --
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-- GNARL is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. --
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-- --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception, --
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-- version 3.1, as published by the Free Software Foundation. --
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-- --
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-- You should have received a copy of the GNU General Public License and --
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-- a copy of the GCC Runtime Library Exception along with this program; --
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-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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-- <http://www.gnu.org/licenses/>. --
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-- --
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-- GNARL was developed by the GNARL team at Florida State University. --
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-- Extensive contributions were provided by Ada Core Technologies, Inc. --
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-- --
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------------------------------------------------------------------------------
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-- This package provides necessary definitions to handle simple (i.e without
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-- entries) protected objects.
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-- All the routines that handle protected objects with entries have been moved
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-- to two children: Entries and Operations. Note that Entries only contains
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-- the type declaration and the OO primitives. This is needed to avoid
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-- circular dependency.
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-- This package is part of the high level tasking interface used by the
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-- compiler to expand Ada 95 tasking constructs into simpler run time calls
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-- (aka GNARLI, GNU Ada Run-time Library Interface)
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-- Note: the compiler generates direct calls to this interface, via Rtsfind.
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-- Any changes to this interface may require corresponding compiler changes
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-- in exp_ch9.adb and possibly exp_ch7.adb and exp_attr.adb
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package System.Tasking.Protected_Objects is
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pragma Elaborate_Body;
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---------------------------------
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-- Compiler Interface (GNARLI) --
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---------------------------------
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-- The compiler will expand in the GNAT tree the following construct:
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-- protected PO is
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-- procedure P;
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-- private
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-- open : boolean := false;
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-- end PO;
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-- protected body PO is
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-- procedure P is
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-- ...variable declarations...
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-- begin
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-- ...B...
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-- end P;
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-- end PO;
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-- as follows:
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-- protected type poT is
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-- procedure p;
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-- private
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-- open : boolean := false;
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-- end poT;
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-- type poTV is limited record
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-- open : boolean := false;
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-- _object : aliased protection;
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-- end record;
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-- procedure poPT__pN (_object : in out poTV);
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-- procedure poPT__pP (_object : in out poTV);
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-- freeze poTV [
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-- procedure poTVI (_init : in out poTV) is
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-- begin
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-- _init.open := false;
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-- object-init-proc (_init._object);
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-- initialize_protection (_init._object'unchecked_access,
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-- unspecified_priority);
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-- return;
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-- end _init_proc;
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-- ]
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-- po : poT;
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-- poTVI (poTV!(po));
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-- procedure poPT__pN (_object : in out poTV) is
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-- poR : protection renames _object._object;
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-- openP : boolean renames _object.open;
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-- ...variable declarations...
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-- begin
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-- ...B...
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-- return;
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-- end poPT__pN;
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-- procedure poPT__pP (_object : in out poTV) is
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-- procedure _clean is
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-- begin
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-- unlock (_object._object'unchecked_access);
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-- return;
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-- end _clean;
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-- begin
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-- lock (_object._object'unchecked_access);
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-- B2b : begin
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-- poPT__pN (_object);
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-- at end
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-- _clean;
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-- end B2b;
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-- return;
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-- end poPT__pP;
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Null_Protected_Entry : constant := Null_Entry;
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Max_Protected_Entry : constant := Max_Entry;
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type Protected_Entry_Index is new Entry_Index
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range Null_Protected_Entry .. Max_Protected_Entry;
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type Barrier_Function_Pointer is access
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function
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(O : System.Address;
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E : Protected_Entry_Index)
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return Boolean;
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-- Pointer to a function which evaluates the barrier of a protected
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-- entry body. O is a pointer to the compiler-generated record
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-- representing the protected object, and E is the index of the
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-- entry serviced by the body.
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type Entry_Action_Pointer is access
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procedure
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(O : System.Address;
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P : System.Address;
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E : Protected_Entry_Index);
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-- Pointer to a procedure which executes the sequence of statements
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-- of a protected entry body. O is a pointer to the compiler-generated
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-- record representing the protected object, P is a pointer to the
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-- record of entry parameters, and E is the index of the
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-- entry serviced by the body.
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type Entry_Body is record
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Barrier : Barrier_Function_Pointer;
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Action : Entry_Action_Pointer;
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end record;
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-- The compiler-generated code passes objects of this type to the GNARL
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-- to allow it to access the executable code of an entry body.
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type Entry_Body_Access is access all Entry_Body;
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type Protection is limited private;
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-- This type contains the GNARL state of a protected object. The
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-- application-defined portion of the state (i.e. private objects)
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-- is maintained by the compiler-generated code.
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-- Note that there are now 2 Protection types. One for the simple
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-- case (no entries) and one for the general case that needs the whole
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-- Finalization mechanism.
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-- This split helps in the case of restricted run time where we want to
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-- minimize the size of the code.
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type Protection_Access is access all Protection;
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Null_PO : constant Protection_Access := null;
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function Get_Ceiling
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(Object : Protection_Access) return System.Any_Priority;
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-- Returns the new ceiling priority of the protected object
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procedure Initialize_Protection
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(Object : Protection_Access;
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Ceiling_Priority : Integer);
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-- Initialize the Object parameter so that it can be used by the runtime
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-- to keep track of the runtime state of a protected object.
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procedure Lock (Object : Protection_Access);
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-- Lock a protected object for write access. Upon return, the caller
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-- owns the lock to this object, and no other call to Lock or
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-- Lock_Read_Only with the same argument will return until the
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-- corresponding call to Unlock has been made by the caller.
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procedure Lock_Read_Only (Object : Protection_Access);
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-- Lock a protected object for read access. Upon return, the caller
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-- owns the lock for read access, and no other calls to Lock with the
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-- same argument will return until the corresponding call to Unlock
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-- has been made by the caller. Other calls to Lock_Read_Only may (but
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-- need not) return before the call to Unlock, and the corresponding
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-- callers will also own the lock for read access.
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procedure Set_Ceiling
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(Object : Protection_Access;
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Prio : System.Any_Priority);
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-- Sets the new ceiling priority of the protected object
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procedure Unlock (Object : Protection_Access);
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-- Relinquish ownership of the lock for the object represented by
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-- the Object parameter. If this ownership was for write access, or
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-- if it was for read access where there are no other read access
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-- locks outstanding, one (or more, in the case of Lock_Read_Only)
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-- of the tasks waiting on this lock (if any) will be given the
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-- lock and allowed to return from the Lock or Lock_Read_Only call.
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private
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type Protection is record
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L : aliased Task_Primitives.Lock;
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-- Lock used to ensure mutual exclusive access to the protected object
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Ceiling : System.Any_Priority;
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-- Ceiling priority associated to the protected object
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New_Ceiling : System.Any_Priority;
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-- New ceiling priority associated to the protected object. In case
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-- of assignment of a new ceiling priority to the protected object the
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-- frontend generates a call to set_ceiling to save the new value in
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-- this field. After such assignment this value can be read by means
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-- of the 'Priority attribute, which generates a call to get_ceiling.
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-- However, the ceiling of the protected object will not be changed
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-- until completion of the protected action in which the assignment
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-- has been executed (AARM D.5.2 (10/2)).
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Owner : Task_Id;
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-- This field contains the protected object's owner. Null_Task
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-- indicates that the protected object is not currently being used.
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-- This information is used for detecting the type of potentially
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-- blocking operations described in the ARM 9.5.1, par. 15 (external
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-- calls on a protected subprogram with the same target object as that
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-- of the protected action).
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end record;
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procedure Finalize_Protection (Object : in out Protection);
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-- Clean up a Protection object (in particular, finalize the associated
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-- Lock object). The compiler generates calls automatically to this
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-- procedure
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end System.Tasking.Protected_Objects;
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