------------------------------------------------------------------------------ -- -- -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS -- -- -- -- SYSTEM.TASKING.PROTECTED_OBJECTS.ENTRIES -- -- -- -- B o d y -- -- -- -- Copyright (C) 1998-2012, 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 -- -- . -- -- -- -- 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.Parameters; 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 Parameters; use Task_Primitives.Operations; ---------------- -- Local Data -- ---------------- Locking_Policy : 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 Single_Lock then Lock_RTS; end if; 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); if Single_Lock then Unlock_RTS; end if; STPO.Write_Lock (Object.L'Unrestricted_Access, Ceiling_Violation); if Ceiling_Violation then raise Program_Error with "Ceiling Violation"; end if; if Single_Lock then Lock_RTS; 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; if Single_Lock then Unlock_RTS; end if; 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_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_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; --------------------- -- Set_Entry_Names -- --------------------- procedure Set_Entry_Names (Object : Protection_Entries_Access; Names : Protected_Entry_Names_Access) is begin Object.Entry_Names := Names; end Set_Entry_Names; -------------------- -- 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;