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------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
-- --
-- S Y S T E M . T A S K I N G . I N I T I A L I Z A T I O N --
-- --
-- S p e c --
-- --
-- Copyright (C) 1992-2009, 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 --
-- <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. --
-- --
------------------------------------------------------------------------------
-- This package provides overall initialization of the tasking portion of the
-- RTS. This package must be elaborated before any tasking features are used.
package System.Tasking.Initialization is
procedure Remove_From_All_Tasks_List (T : Task_Id);
-- Remove T from All_Tasks_List. Call this function with RTS_Lock taken
---------------------------------
-- Tasking-Specific Soft Links --
---------------------------------
-- These permit us to leave out certain portions of the tasking
-- run-time system if they are not used. They are only used internally
-- by the tasking run-time system.
-- So far, the only example is support for Ada.Task_Attributes
type Proc_T is access procedure (T : Task_Id);
procedure Finalize_Attributes (T : Task_Id);
procedure Initialize_Attributes (T : Task_Id);
Finalize_Attributes_Link : Proc_T := Finalize_Attributes'Access;
-- should be called with abort deferred and T.L write-locked
Initialize_Attributes_Link : Proc_T := Initialize_Attributes'Access;
-- should be called with abort deferred, but holding no locks
-------------------------
-- Abort Defer/Undefer --
-------------------------
-- Defer_Abort defers the affects of low-level abort and priority change
-- in the calling task until a matching Undefer_Abort call is executed.
-- Undefer_Abort DOES MORE than just undo the effects of one call to
-- Defer_Abort. It is the universal "polling point" for deferred
-- processing, including the following:
-- 1) base priority changes
-- 2) abort/ATC
-- Abort deferral MAY be nested (Self_ID.Deferral_Level is a count), but
-- to avoid waste and undetected errors, it generally SHOULD NOT be
-- nested. The symptom of over-deferring abort is that an exception may
-- fail to be raised, or an abort may fail to take place.
-- Therefore, there are two sets of the inlineable defer/undefer routines,
-- which are the ones to be used inside GNARL. One set allows nesting. The
-- other does not. People who maintain the GNARL should try to avoid using
-- the nested versions, or at least look very critically at the places
-- where they are used.
-- In general, any GNARL call that is potentially blocking, or whose
-- semantics require that it sometimes raise an exception, or that is
-- required to be an abort completion point, must be made with abort
-- Deferral_Level = 1.
-- In general, non-blocking GNARL calls, which may be made from inside a
-- protected action, are likely to need to allow nested abort deferral.
-- With some critical exceptions (which are supposed to be documented),
-- internal calls to the tasking runtime system assume abort is already
-- deferred, and do not modify the deferral level.
-- There is also a set of non-inlineable defer/undefer routines, for direct
-- call from the compiler. These are not inlineable because they may need
-- to be called via pointers ("soft links"). For the sake of efficiency,
-- the version with Self_ID as parameter should used wherever possible.
-- These are all nestable.
-- Non-nestable inline versions
procedure Defer_Abort (Self_ID : Task_Id);
pragma Inline (Defer_Abort);
procedure Undefer_Abort (Self_ID : Task_Id);
pragma Inline (Undefer_Abort);
-- Nestable inline versions
procedure Defer_Abort_Nestable (Self_ID : Task_Id);
pragma Inline (Defer_Abort_Nestable);
procedure Undefer_Abort_Nestable (Self_ID : Task_Id);
pragma Inline (Undefer_Abort_Nestable);
procedure Do_Pending_Action (Self_ID : Task_Id);
-- Only call with no locks, and when Self_ID.Pending_Action = True Perform
-- necessary pending actions (e.g. abort, priority change). This procedure
-- is usually called when needed as a result of calling Undefer_Abort,
-- although in the case of e.g. No_Abort restriction, it can be necessary
-- to force execution of pending actions.
function Check_Abort_Status return Integer;
-- Returns Boolean'Pos (True) iff abort signal should raise
-- Standard.Abort_Signal. Only used by IRIX currently.
--------------------------
-- Change Base Priority --
--------------------------
procedure Change_Base_Priority (T : Task_Id);
-- Change the base priority of T. Has to be called with the affected
-- task's ATCB write-locked. May temporarily release the lock.
----------------------
-- Task Lock/Unlock --
----------------------
procedure Task_Lock (Self_ID : Task_Id);
pragma Inline (Task_Lock);
procedure Task_Unlock (Self_ID : Task_Id);
pragma Inline (Task_Unlock);
-- These are versions of Lock_Task and Unlock_Task created for use
-- within the GNARL.
procedure Final_Task_Unlock (Self_ID : Task_Id);
-- This version is only for use in Terminate_Task, when the task is
-- relinquishing further rights to its own ATCB. There is a very
-- interesting potential race condition there, where the old task may run
-- concurrently with a new task that is allocated the old tasks (now
-- reused) ATCB. The critical thing here is to not make any reference to
-- the ATCB after the lock is released. See also comments on
-- Terminate_Task and Unlock.
procedure Wakeup_Entry_Caller
(Self_ID : Task_Id;
Entry_Call : Entry_Call_Link;
New_State : Entry_Call_State);
pragma Inline (Wakeup_Entry_Caller);
-- This is called at the end of service of an entry call, to abort the
-- caller if he is in an abortable part, and to wake up the caller if he
-- is on Entry_Caller_Sleep. Call it holding the lock of Entry_Call.Self.
--
-- Timed_Call or Simple_Call:
-- The caller is waiting on Entry_Caller_Sleep, in Wait_For_Completion,
-- or Wait_For_Completion_With_Timeout.
--
-- Conditional_Call:
-- The caller might be in Wait_For_Completion,
-- waiting for a rendezvous (possibly requeued without abort) to
-- complete.
--
-- Asynchronous_Call:
-- The caller may be executing in the abortable part an async. select,
-- or on a time delay, if Entry_Call.State >= Was_Abortable.
procedure Locked_Abort_To_Level
(Self_ID : Task_Id;
T : Task_Id;
L : ATC_Level);
pragma Inline (Locked_Abort_To_Level);
-- Abort a task to a specified ATC level. Call this only with T locked
end System.Tasking.Initialization;
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