| ------------------------------------------------------------------------------ |
| -- -- |
| -- 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) 1991-2017, Florida State University -- |
| -- Copyright (C) 1995-2022, 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. -- |
| -- -- |
| ------------------------------------------------------------------------------ |
| |
| with System.Task_Primitives.Operations; |
| 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; |
| |
| ---------------- |
| -- Local Data -- |
| ---------------- |
| |
| Locking_Policy : constant 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 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 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); |
| |
| 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; |
