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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 --
-- --
-- B o d y --
-- --
-- Copyright (C) 1991-1994, Florida State University --
-- Copyright (C) 1995-2014, AdaCore --
-- --
-- GNAT 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 Polling (Off);
-- Turn off polling, we do not want ATC polling to take place during tasking
-- operations. It causes infinite loops and other problems.
with System.Task_Primitives.Operations;
with System.Parameters;
with System.Traces;
with System.Soft_Links.Tasking;
with System.Secondary_Stack;
pragma Elaborate_All (System.Secondary_Stack);
pragma Unreferenced (System.Secondary_Stack);
-- Make sure the body of Secondary_Stack is elaborated before calling
-- Init_Tasking_Soft_Links. See comments for this routine for explanation.
package body System.Tasking.Protected_Objects is
use System.Task_Primitives.Operations;
use System.Traces;
----------------
-- Local Data --
----------------
Locking_Policy : Character;
pragma Import (C, Locking_Policy, "__gl_locking_policy");
-------------------------
-- Finalize_Protection --
-------------------------
procedure Finalize_Protection (Object : in out Protection) is
begin
Finalize_Lock (Object.L'Unrestricted_Access);
end Finalize_Protection;
---------------------------
-- Initialize_Protection --
---------------------------
procedure Initialize_Protection
(Object : Protection_Access;
Ceiling_Priority : Integer)
is
Init_Priority : Integer := Ceiling_Priority;
begin
if Init_Priority = Unspecified_Priority then
Init_Priority := System.Priority'Last;
end if;
Initialize_Lock (Init_Priority, Object.L'Access);
Object.Ceiling := System.Any_Priority (Init_Priority);
Object.New_Ceiling := System.Any_Priority (Init_Priority);
Object.Owner := Null_Task;
end Initialize_Protection;
-----------------
-- Get_Ceiling --
-----------------
function Get_Ceiling
(Object : Protection_Access) return System.Any_Priority is
begin
return Object.New_Ceiling;
end Get_Ceiling;
----------
-- Lock --
----------
procedure Lock (Object : Protection_Access) is
Ceiling_Violation : Boolean;
begin
-- The lock is made without deferring abort
-- Therefore the abort has to be deferred before calling this routine.
-- This means that the compiler has to generate a Defer_Abort call
-- before the call to Lock.
-- The caller is responsible for undeferring abort, and compiler
-- generated calls must be protected with cleanup handlers to ensure
-- that abort is undeferred in all cases.
-- If pragma Detect_Blocking is active then, as described in the ARM
-- 9.5.1, par. 15, we must check whether this is an external call on a
-- protected subprogram with the same target object as that of the
-- protected action that is currently in progress (i.e., if the caller
-- is already the protected object's owner). If this is the case hence
-- Program_Error must be raised.
if Detect_Blocking and then Object.Owner = Self then
raise Program_Error;
end if;
Write_Lock (Object.L'Access, Ceiling_Violation);
if Parameters.Runtime_Traces then
Send_Trace_Info (PO_Lock);
end if;
if Ceiling_Violation then
raise Program_Error;
end if;
-- We are entering in a protected action, so that we increase the
-- protected object nesting level (if pragma Detect_Blocking is
-- active), and update the protected object's owner.
if Detect_Blocking then
declare
Self_Id : constant Task_Id := Self;
begin
-- Update the protected object's owner
Object.Owner := Self_Id;
-- Increase protected object nesting level
Self_Id.Common.Protected_Action_Nesting :=
Self_Id.Common.Protected_Action_Nesting + 1;
end;
end if;
end Lock;
--------------------
-- Lock_Read_Only --
--------------------
procedure Lock_Read_Only (Object : Protection_Access) is
Ceiling_Violation : Boolean;
begin
-- If pragma Detect_Blocking is active then, as described in the ARM
-- 9.5.1, par. 15, we must check whether this is an external call on
-- protected subprogram with the same target object as that of the
-- protected action that is currently in progress (i.e., if the caller
-- is already the protected object's owner). If this is the case hence
-- Program_Error must be raised.
--
-- Note that in this case (getting read access), several tasks may have
-- read ownership of the protected object, so that this method of
-- storing the (single) protected object's owner does not work reliably
-- for read locks. However, this is the approach taken for two major
-- reasons: first, this function is not currently being used (it is
-- provided for possible future use), and second, it largely simplifies
-- the implementation.
if Detect_Blocking and then Object.Owner = Self then
raise Program_Error;
end if;
Read_Lock (Object.L'Access, Ceiling_Violation);
if Parameters.Runtime_Traces then
Send_Trace_Info (PO_Lock);
end if;
if Ceiling_Violation then
raise Program_Error;
end if;
-- We are entering in a protected action, so we increase the protected
-- object nesting level (if pragma Detect_Blocking is active).
if Detect_Blocking then
declare
Self_Id : constant Task_Id := Self;
begin
-- Update the protected object's owner
Object.Owner := Self_Id;
-- Increase protected object nesting level
Self_Id.Common.Protected_Action_Nesting :=
Self_Id.Common.Protected_Action_Nesting + 1;
end;
end if;
end Lock_Read_Only;
-----------------
-- Set_Ceiling --
-----------------
procedure Set_Ceiling
(Object : Protection_Access;
Prio : System.Any_Priority) is
begin
Object.New_Ceiling := Prio;
end Set_Ceiling;
------------
-- Unlock --
------------
procedure Unlock (Object : Protection_Access) is
begin
-- We are exiting from a protected action, so that we decrease the
-- protected object nesting level (if pragma Detect_Blocking is
-- active), and remove ownership of the protected object.
if Detect_Blocking then
declare
Self_Id : constant Task_Id := Self;
begin
-- Calls to this procedure can only take place when being within
-- a protected action and when the caller is the protected
-- object's owner.
pragma Assert (Self_Id.Common.Protected_Action_Nesting > 0
and then Object.Owner = Self_Id);
-- Remove ownership of the protected object
Object.Owner := Null_Task;
-- We are exiting from a protected action, so we decrease the
-- protected object nesting level.
Self_Id.Common.Protected_Action_Nesting :=
Self_Id.Common.Protected_Action_Nesting - 1;
end;
end if;
-- Before releasing the mutex we must actually update its ceiling
-- priority if it has been changed.
if Object.New_Ceiling /= Object.Ceiling then
if Locking_Policy = 'C' then
System.Task_Primitives.Operations.Set_Ceiling
(Object.L'Access, Object.New_Ceiling);
end if;
Object.Ceiling := Object.New_Ceiling;
end if;
Unlock (Object.L'Access);
if Parameters.Runtime_Traces then
Send_Trace_Info (PO_Unlock);
end if;
end Unlock;
begin
-- Ensure that tasking is initialized, as well as tasking soft links
-- when using protected objects.
Tasking.Initialize;
System.Soft_Links.Tasking.Init_Tasking_Soft_Links;
end System.Tasking.Protected_Objects;
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