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-- --
-- --
-- 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) 1992-2001, 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 2, or (at your option) any later ver- --
-- sion. GNARL 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. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNARL; see file COPYING. If not, write --
-- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
-- MA 02111-1307, USA. --
-- --
-- As a special exception, if other files instantiate generics from this --
-- unit, or you link this unit with other files to produce an executable, --
-- this unit does not by itself cause the resulting executable to be --
-- covered by the GNU General Public License. This exception does not --
-- however invalidate any other reasons why the executable file might be --
-- covered by the GNU Public License. --
-- --
-- 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 abortion deferred and T.L write-locked
Initialize_Attributes_Link : Proc_T := Initialize_Attributes'Access;
-- should be called with abortion 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 inlinable 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-linable defer/undefer routines,
-- for direct call from the compiler. These are not in-lineable
-- 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);
-- NON-INLINE versions without Self_ID for code generated by the
-- expander and for soft links
procedure Defer_Abortion;
procedure Undefer_Abortion;
-- ?????
-- Try to phase out all uses of the above versions.
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 temporariliy release the lock.
procedure Poll_Base_Priority_Change (Self_ID : Task_ID);
-- Has to be called with Self_ID's ATCB write-locked.
-- May temporariliy release the lock.
pragma Inline (Poll_Base_Priority_Change);
-- 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 o
-- 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;