------------------------------------------------------------------------------ -- -- -- 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) 1995-2011, 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 -- -- . -- -- -- -- 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; 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;