------------------------------------------------------------------------------
-- --
--- GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS --
+-- 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) 1995-2005, Ada Core Technologies --
+-- Copyright (C) 1995-2006, AdaCore --
-- --
-- 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- --
-- 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. --
+-- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
+-- Boston, MA 02110-1301, 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, --
Ceiling_Priority : Integer)
is
Init_Priority : Integer := Ceiling_Priority;
+
begin
if Init_Priority = Unspecified_Priority then
Init_Priority := System.Priority'Last;
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 --
----------
-- 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
-- We are entering in a protected action, so that we increase the
-- protected object nesting level (if pragma Detect_Blocking is
- -- active).
+ -- 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;
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
+ -- reasosn: 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
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).
+ -- 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 --
------------
begin
-- We are exiting from a protected action, so that we decrease the
-- protected object nesting level (if pragma Detect_Blocking is
- -- active).
+ -- active), and remove ownership of the protected object.
if Detect_Blocking then
declare
Self_Id : constant Task_Id := Self;
begin
- -- Cannot call this procedure without being within a protected
- -- action.
+ -- 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;
- pragma Assert (Self_Id.Common.Protected_Action_Nesting > 0);
+ -- 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 Unlock;
begin
- -- Ensure that tasking soft links are set when using protected objects
+ -- 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;
OSDN Git Service
