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------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
-- --
-- SYSTEM.TASKING.PROTECTED_OBJECTS.ENTRIES --
-- --
-- B o d y --
-- --
-- Copyright (C) 1998-2022, 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. --
-- --
------------------------------------------------------------------------------
-- 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
with System.Task_Primitives.Operations;
with System.Restrictions;
with System.Tasking.Initialization;
pragma Elaborate_All (System.Tasking.Initialization);
-- To insure that tasking is initialized if any protected objects are created
package body System.Tasking.Protected_Objects.Entries is
package STPO renames System.Task_Primitives.Operations;
use Task_Primitives.Operations;
----------------
-- Local Data --
----------------
Locking_Policy : constant Character;
pragma Import (C, Locking_Policy, "__gl_locking_policy");
--------------
-- Finalize --
--------------
overriding procedure Finalize (Object : in out Protection_Entries) is
Entry_Call : Entry_Call_Link;
Caller : Task_Id;
Ceiling_Violation : Boolean;
Self_ID : constant Task_Id := STPO.Self;
Old_Base_Priority : System.Any_Priority;
begin
if Object.Finalized then
return;
end if;
STPO.Write_Lock (Object.L'Unrestricted_Access, Ceiling_Violation);
if Ceiling_Violation then
-- Dip our own priority down to ceiling of lock. See similar code in
-- Tasking.Entry_Calls.Lock_Server.
STPO.Write_Lock (Self_ID);
Old_Base_Priority := Self_ID.Common.Base_Priority;
Self_ID.New_Base_Priority := Object.Ceiling;
Initialization.Change_Base_Priority (Self_ID);
STPO.Unlock (Self_ID);
STPO.Write_Lock (Object.L'Unrestricted_Access, Ceiling_Violation);
if Ceiling_Violation then
raise Program_Error with "ceiling violation";
end if;
Object.Old_Base_Priority := Old_Base_Priority;
Object.Pending_Action := True;
end if;
-- Send program_error to all tasks still queued on this object
for E in Object.Entry_Queues'Range loop
Entry_Call := Object.Entry_Queues (E).Head;
while Entry_Call /= null loop
Caller := Entry_Call.Self;
Entry_Call.Exception_To_Raise := Program_Error'Identity;
STPO.Write_Lock (Caller);
Initialization.Wakeup_Entry_Caller (Self_ID, Entry_Call, Done);
STPO.Unlock (Caller);
exit when Entry_Call = Object.Entry_Queues (E).Tail;
Entry_Call := Entry_Call.Next;
end loop;
end loop;
Object.Finalized := True;
STPO.Unlock (Object.L'Unrestricted_Access);
STPO.Finalize_Lock (Object.L'Unrestricted_Access);
end Finalize;
-----------------
-- Get_Ceiling --
-----------------
function Get_Ceiling
(Object : Protection_Entries_Access) return System.Any_Priority is
begin
return Object.New_Ceiling;
end Get_Ceiling;
-------------------------------------
-- Has_Interrupt_Or_Attach_Handler --
-------------------------------------
function Has_Interrupt_Or_Attach_Handler
(Object : Protection_Entries_Access)
return Boolean
is
pragma Warnings (Off, Object);
begin
return False;
end Has_Interrupt_Or_Attach_Handler;
-----------------------------------
-- Initialize_Protection_Entries --
-----------------------------------
procedure Initialize_Protection_Entries
(Object : Protection_Entries_Access;
Ceiling_Priority : Integer;
Compiler_Info : System.Address;
Entry_Queue_Maxes : Protected_Entry_Queue_Max_Access;
Entry_Bodies : Protected_Entry_Body_Access;
Find_Body_Index : Find_Body_Index_Access)
is
Init_Priority : Integer := Ceiling_Priority;
Self_ID : constant Task_Id := STPO.Self;
begin
if Init_Priority = Unspecified_Priority then
Init_Priority := System.Priority'Last;
end if;
if Locking_Policy = 'C'
and then Has_Interrupt_Or_Attach_Handler (Object)
and then Init_Priority not in System.Interrupt_Priority
then
-- Required by C.3.1(11)
raise Program_Error;
end if;
-- If a PO is created from a controlled operation, abort is already
-- deferred at this point, so we need to use Defer_Abort_Nestable. In
-- some cases, the following assertion can help to spot inconsistencies,
-- outside the above scenario involving controlled types.
-- pragma Assert (Self_Id.Deferral_Level = 0);
Initialization.Defer_Abort_Nestable (Self_ID);
Initialize_Lock (Init_Priority, Object.L'Access);
Initialization.Undefer_Abort_Nestable (Self_ID);
Object.Ceiling := System.Any_Priority (Init_Priority);
Object.New_Ceiling := System.Any_Priority (Init_Priority);
Object.Owner := Null_Task;
Object.Compiler_Info := Compiler_Info;
Object.Pending_Action := False;
Object.Call_In_Progress := null;
Object.Entry_Queue_Maxes := Entry_Queue_Maxes;
Object.Entry_Bodies := Entry_Bodies;
Object.Find_Body_Index := Find_Body_Index;
for E in Object.Entry_Queues'Range loop
Object.Entry_Queues (E).Head := null;
Object.Entry_Queues (E).Tail := null;
end loop;
end Initialize_Protection_Entries;
------------------
-- Lock_Entries --
------------------
procedure Lock_Entries (Object : Protection_Entries_Access) is
Ceiling_Violation : Boolean;
begin
Lock_Entries_With_Status (Object, Ceiling_Violation);
if Ceiling_Violation then
raise Program_Error with "ceiling violation";
end if;
end Lock_Entries;
------------------------------
-- Lock_Entries_With_Status --
------------------------------
procedure Lock_Entries_With_Status
(Object : Protection_Entries_Access;
Ceiling_Violation : out Boolean)
is
begin
if Object.Finalized then
raise Program_Error with "protected object is finalized";
end if;
-- 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;
-- 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.
pragma Assert
(STPO.Self.Deferral_Level > 0
or else not Restrictions.Abort_Allowed);
Write_Lock (Object.L'Access, Ceiling_Violation);
-- 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_Entries_With_Status;
----------------------------
-- Lock_Read_Only_Entries --
----------------------------
procedure Lock_Read_Only_Entries (Object : Protection_Entries_Access) is
Ceiling_Violation : Boolean;
begin
if Object.Finalized then
raise Program_Error with "protected object is finalized";
end if;
-- 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.
-- 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 Ceiling_Violation then
raise Program_Error with "ceiling violation";
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_Read_Only_Entries;
-----------------------
-- Number_Of_Entries --
-----------------------
function Number_Of_Entries
(Object : Protection_Entries_Access) return Entry_Index
is
begin
return Entry_Index (Object.Num_Entries);
end Number_Of_Entries;
-----------------
-- Set_Ceiling --
-----------------
procedure Set_Ceiling
(Object : Protection_Entries_Access;
Prio : System.Any_Priority) is
begin
Object.New_Ceiling := Prio;
end Set_Ceiling;
--------------------
-- Unlock_Entries --
--------------------
procedure Unlock_Entries (Object : Protection_Entries_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;
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);
end Unlock_Entries;
end System.Tasking.Protected_Objects.Entries;