| ------------------------------------------------------------------------------ |
| -- -- |
| -- 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, 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- -- |
| -- 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, 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, -- |
| -- 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. -- |
| -- -- |
| ------------------------------------------------------------------------------ |
| |
| 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; |
| -- used for Write_Lock |
| -- Unlock |
| -- Self |
| |
| with System.Parameters; |
| -- used for Runtime_Traces |
| |
| with System.Traces; |
| -- used for Send_Trace_Info |
| |
| with System.Soft_Links.Tasking; |
| -- Used for Init_Tasking_Soft_Links |
| |
| package body System.Tasking.Protected_Objects is |
| |
| use System.Task_Primitives.Operations; |
| use System.Traces; |
| |
| ------------------------- |
| -- 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.Owner := Null_Task; |
| end Initialize_Protection; |
| |
| ---------- |
| -- Lock -- |
| ---------- |
| |
| procedure Lock (Object : Protection_Access) is |
| Ceiling_Violation : Boolean; |
| |
| begin |
| -- The lock is made without defering 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 |
| -- 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 |
| 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; |
| |
| ------------ |
| -- 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; |
| |
| 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; |
