237 lines
12 KiB
Ada
237 lines
12 KiB
Ada
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------------------------------------------------------------------------------
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-- --
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-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
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-- --
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-- SYSTEM.TASKING.PROTECTED_OBJECTS.ENTRIES --
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 1992-2020, Free Software Foundation, Inc. --
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-- --
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-- GNARL is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. --
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-- --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception, --
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-- version 3.1, as published by the Free Software Foundation. --
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-- --
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-- You should have received a copy of the GNU General Public License and --
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-- a copy of the GCC Runtime Library Exception along with this program; --
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-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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-- <http://www.gnu.org/licenses/>. --
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-- --
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-- GNARL was developed by the GNARL team at Florida State University. --
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-- Extensive contributions were provided by Ada Core Technologies, Inc. --
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-- --
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------------------------------------------------------------------------------
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-- This package contains all simple primitives related to Protected_Objects
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-- with entries (i.e init, lock, unlock).
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-- The handling of protected objects with no entries is done in
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-- System.Tasking.Protected_Objects, the complex routines for protected
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-- objects with entries in System.Tasking.Protected_Objects.Operations.
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-- The split between Entries and Operations is needed to break circular
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-- dependencies inside the run time.
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-- Note: the compiler generates direct calls to this interface, via Rtsfind.
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-- Any changes to this interface may require corresponding compiler changes.
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with Ada.Finalization;
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with Ada.Unchecked_Conversion;
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package System.Tasking.Protected_Objects.Entries is
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pragma Elaborate_Body;
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subtype Positive_Protected_Entry_Index is
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Protected_Entry_Index range 1 .. Protected_Entry_Index'Last;
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-- Index of the entry (and in some cases of the queue)
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type Find_Body_Index_Access is access
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function
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(O : System.Address;
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E : Protected_Entry_Index)
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return Protected_Entry_Index;
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-- Convert a queue index to an entry index (an entry family has one entry
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-- index for several queue indexes).
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type Protected_Entry_Body_Array is
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array (Positive_Protected_Entry_Index range <>) of Entry_Body;
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-- Contains executable code for all entry bodies of a protected type
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type Protected_Entry_Body_Access is
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access constant Protected_Entry_Body_Array;
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type Protected_Entry_Queue_Array is
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array (Protected_Entry_Index range <>) of Entry_Queue;
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type Protected_Entry_Queue_Max_Array is
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array (Positive_Protected_Entry_Index range <>) of Natural;
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type Protected_Entry_Queue_Max_Access is
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access constant Protected_Entry_Queue_Max_Array;
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-- The following type contains the GNARL state of a protected object.
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-- The application-defined portion of the state (i.e. private objects)
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-- is maintained by the compiler-generated code. Note that there is a
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-- simplified version of this type declared in System.Tasking.PO_Simple
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-- that handle the simple case (no entries).
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type Protection_Entries (Num_Entries : Protected_Entry_Index) is new
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Ada.Finalization.Limited_Controlled
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with record
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L : aliased Task_Primitives.Lock;
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-- The underlying lock associated with a Protection_Entries. Note
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-- that you should never (un)lock Object.L directly, but instead
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-- use Lock_Entries/Unlock_Entries.
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Compiler_Info : System.Address;
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-- Pointer to compiler-generated record representing protected object
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Call_In_Progress : Entry_Call_Link;
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-- Pointer to the entry call being executed (if any)
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Ceiling : System.Any_Priority;
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-- Ceiling priority associated with the protected object
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New_Ceiling : System.Any_Priority;
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-- New ceiling priority associated to the protected object. In case
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-- of assignment of a new ceiling priority to the protected object the
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-- frontend generates a call to set_ceiling to save the new value in
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-- this field. After such assignment this value can be read by means
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-- of the 'Priority attribute, which generates a call to get_ceiling.
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-- However, the ceiling of the protected object will not be changed
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-- until completion of the protected action in which the assignment
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-- has been executed (AARM D.5.2 (10/2)).
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Owner : Task_Id;
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-- This field contains the protected object's owner. Null_Task
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-- indicates that the protected object is not currently being used.
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-- This information is used for detecting the type of potentially
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-- blocking operations described in the ARM 9.5.1, par. 15 (external
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-- calls on a protected subprogram with the same target object as that
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-- of the protected action).
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Old_Base_Priority : System.Any_Priority;
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-- Task's base priority when the protected operation was called
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Pending_Action : Boolean;
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-- Flag indicating that priority has been dipped temporarily in order
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-- to avoid violating the priority ceiling of the lock associated with
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-- this protected object, in Lock_Server. The flag tells Unlock_Server
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-- or Unlock_And_Update_Server to restore the old priority to
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-- Old_Base_Priority. This is needed because of situations (bad
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-- language design?) where one needs to lock a PO but to do so would
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-- violate the priority ceiling. For example, this can happen when an
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-- entry call has been requeued to a lower-priority object, and the
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-- caller then tries to cancel the call while its own priority is
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-- higher than the ceiling of the new PO.
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Finalized : Boolean := False;
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-- Set to True by Finalize to make this routine idempotent
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Entry_Bodies : Protected_Entry_Body_Access;
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-- Pointer to an array containing the executable code for all entry
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-- bodies of a protected type.
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Find_Body_Index : Find_Body_Index_Access;
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-- A function which maps the entry index in a call (which denotes the
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-- queue of the proper entry) into the body of the entry.
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Entry_Queue_Maxes : Protected_Entry_Queue_Max_Access;
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-- Access to an array of naturals representing the max value for each
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-- entry's queue length. A value of 0 signifies no max.
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Entry_Queues : Protected_Entry_Queue_Array (1 .. Num_Entries);
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-- Action and barrier subprograms for the protected type.
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end record;
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-- No default initial values for this type, since call records will need to
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-- be re-initialized before every use.
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type Protection_Entries_Access is access all Protection_Entries'Class;
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-- See comments in s-tassta.adb about the implicit call to Current_Master
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-- generated by this declaration.
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function To_Address is
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new Ada.Unchecked_Conversion (Protection_Entries_Access, System.Address);
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function To_Protection is
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new Ada.Unchecked_Conversion (System.Address, Protection_Entries_Access);
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function Get_Ceiling
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(Object : Protection_Entries_Access) return System.Any_Priority;
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-- Returns the new ceiling priority of the protected object
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function Has_Interrupt_Or_Attach_Handler
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(Object : Protection_Entries_Access) return Boolean;
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-- Returns True if an Interrupt_Handler or Attach_Handler pragma applies
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-- to the protected object. That is to say this primitive returns False for
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-- Protection, but is overridden to return True when interrupt handlers are
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-- declared so the check required by C.3.1(11) can be implemented in
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-- System.Tasking.Protected_Objects.Initialize_Protection.
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procedure Initialize_Protection_Entries
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(Object : Protection_Entries_Access;
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Ceiling_Priority : Integer;
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Compiler_Info : System.Address;
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Entry_Queue_Maxes : Protected_Entry_Queue_Max_Access;
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Entry_Bodies : Protected_Entry_Body_Access;
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Find_Body_Index : Find_Body_Index_Access);
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-- Initialize the Object parameter so that it can be used by the runtime
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-- to keep track of the runtime state of a protected object.
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procedure Lock_Entries (Object : Protection_Entries_Access);
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-- Lock a protected object for write access. Upon return, the caller owns
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-- the lock to this object, and no other call to Lock or Lock_Read_Only
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-- with the same argument will return until the corresponding call to
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-- Unlock has been made by the caller. Program_Error is raised in case of
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-- ceiling violation.
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procedure Lock_Entries_With_Status
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(Object : Protection_Entries_Access;
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Ceiling_Violation : out Boolean);
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-- Same as above, but return the ceiling violation status instead of
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-- raising Program_Error.
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procedure Lock_Read_Only_Entries (Object : Protection_Entries_Access);
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-- Lock a protected object for read access. Upon return, the caller owns
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-- the lock for read access, and no other calls to Lock with the same
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-- argument will return until the corresponding call to Unlock has been
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-- made by the caller. Other calls to Lock_Read_Only may (but need not)
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-- return before the call to Unlock, and the corresponding callers will
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-- also own the lock for read access.
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--
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-- Note: we are not currently using this interface, it is provided for
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-- possible future use. At the current time, everyone uses Lock for both
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-- read and write locks.
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function Number_Of_Entries
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(Object : Protection_Entries_Access) return Entry_Index;
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-- Return the number of entries of a protected object
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procedure Set_Ceiling
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(Object : Protection_Entries_Access;
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Prio : System.Any_Priority);
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-- Sets the new ceiling priority of the protected object
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procedure Unlock_Entries (Object : Protection_Entries_Access);
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-- Relinquish ownership of the lock for the object represented by the
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-- Object parameter. If this ownership was for write access, or if it was
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-- for read access where there are no other read access locks outstanding,
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-- one (or more, in the case of Lock_Read_Only) of the tasks waiting on
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-- this lock (if any) will be given the lock and allowed to return from
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-- the Lock or Lock_Read_Only call.
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private
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overriding procedure Finalize (Object : in out Protection_Entries);
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-- Clean up a Protection object; in particular, finalize the associated
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-- Lock object.
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end System.Tasking.Protected_Objects.Entries;
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