1224 lines
49 KiB
Ada
1224 lines
49 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
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-- --
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-- S Y S T E M . T A S K I N G --
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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 provides necessary type definitions for compiler interface
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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.Exceptions;
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with Ada.Unchecked_Conversion;
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with System.Multiprocessors;
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with System.Parameters;
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with System.Soft_Links;
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with System.Stack_Usage;
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with System.Task_Info;
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with System.Task_Primitives;
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package System.Tasking is
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pragma Preelaborate;
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-------------------
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-- Locking Rules --
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-------------------
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-- The following rules must be followed at all times, to prevent
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-- deadlock and generally ensure correct operation of locking.
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-- Never lock a lock unless abort is deferred
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-- Never undefer abort while holding a lock
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-- Overlapping critical sections must be properly nested, and locks must
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-- be released in LIFO order. E.g., the following is not allowed:
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-- Lock (X);
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-- ...
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-- Lock (Y);
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-- ...
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-- Unlock (X);
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-- ...
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-- Unlock (Y);
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-- Locks with lower (smaller) level number cannot be locked
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-- while holding a lock with a higher level number. (The level
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-- 1. System.Tasking.PO_Simple.Protection.L (any PO lock)
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-- 2. System.Tasking.Initialization.Global_Task_Lock (in body)
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-- 3. System.Task_Primitives.Operations.Single_RTS_Lock
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-- 4. System.Tasking.Ada_Task_Control_Block.LL.L (any TCB lock)
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-- Clearly, there can be no circular chain of hold-and-wait
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-- relationships involving locks in different ordering levels.
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-- We used to have Global_Task_Lock before Protection.L but this was
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-- clearly wrong since there can be calls to "new" inside protected
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-- operations. The new ordering prevents these failures.
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-- Sometimes we need to hold two ATCB locks at the same time. To allow us
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-- to order the locking, each ATCB is given a unique serial number. If one
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-- needs to hold locks on two ATCBs at once, the lock with lower serial
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-- number must be locked first. We avoid holding three or more ATCB locks,
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-- because that can easily lead to complications that cause race conditions
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-- and deadlocks.
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-- We don't always need to check the serial numbers, since the serial
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-- numbers are assigned sequentially, and so:
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-- . The parent of a task always has a lower serial number.
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-- . The activator of a task always has a lower serial number.
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-- . The environment task has a lower serial number than any other task.
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-- . If the activator of a task is different from the task's parent,
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-- the parent always has a lower serial number than the activator.
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---------------------------------
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-- Task_Id related definitions --
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---------------------------------
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type Ada_Task_Control_Block;
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type Task_Id is access all Ada_Task_Control_Block;
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for Task_Id'Size use System.Task_Primitives.Task_Address_Size;
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Null_Task : constant Task_Id;
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type Task_List is array (Positive range <>) of Task_Id;
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function Self return Task_Id;
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pragma Inline (Self);
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-- This is the compiler interface version of this function. Do not call
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-- from the run-time system.
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function To_Task_Id is
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new Ada.Unchecked_Conversion
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(System.Task_Primitives.Task_Address, Task_Id);
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function To_Address is
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new Ada.Unchecked_Conversion
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(Task_Id, System.Task_Primitives.Task_Address);
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-----------------------
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-- Enumeration types --
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-----------------------
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type Task_States is
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(Unactivated,
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-- TCB initialized but not task has not been created.
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-- It cannot be executing.
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-- Activating,
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-- -- ??? Temporarily at end of list for GDB compatibility
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-- -- Task has been created and is being made Runnable.
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-- Active states
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-- For all states from here down, the task has been activated.
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-- For all states from here down, except for Terminated, the task
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-- may be executing.
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-- Activator = null iff it has not yet completed activating.
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Runnable,
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-- Task is not blocked for any reason known to Ada.
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-- (It may be waiting for a mutex, though.)
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-- It is conceptually "executing" in normal mode.
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Terminated,
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-- The task is terminated, in the sense of ARM 9.3 (5).
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-- Any dependents that were waiting on terminate
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-- alternatives have been awakened and have terminated themselves.
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Activator_Sleep,
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-- Task is waiting for created tasks to complete activation
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Acceptor_Sleep,
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-- Task is waiting on an accept or select with terminate
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-- Acceptor_Delay_Sleep,
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-- -- ??? Temporarily at end of list for GDB compatibility
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-- -- Task is waiting on an selective wait statement
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Entry_Caller_Sleep,
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-- Task is waiting on an entry call
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Async_Select_Sleep,
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-- Task is waiting to start the abortable part of an
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-- asynchronous select statement.
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Delay_Sleep,
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-- Task is waiting on a select statement with only a delay
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-- alternative open.
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Master_Completion_Sleep,
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-- Master completion has two phases.
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-- In Phase 1 the task is sleeping in Complete_Master
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-- having completed a master within itself,
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-- and is waiting for the tasks dependent on that master to become
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-- terminated or waiting on a terminate Phase.
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Master_Phase_2_Sleep,
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-- In Phase 2 the task is sleeping in Complete_Master
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-- waiting for tasks on terminate alternatives to finish
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-- terminating.
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-- The following are special uses of sleep, for server tasks
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-- within the run-time system.
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Interrupt_Server_Idle_Sleep,
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Interrupt_Server_Blocked_Interrupt_Sleep,
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Timer_Server_Sleep,
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AST_Server_Sleep,
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Asynchronous_Hold,
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-- The task has been held by Asynchronous_Task_Control.Hold_Task
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Interrupt_Server_Blocked_On_Event_Flag,
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-- The task has been blocked on a system call waiting for a
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-- completion event/signal to occur.
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Activating,
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-- Task has been created and is being made Runnable
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Acceptor_Delay_Sleep
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-- Task is waiting on an selective wait statement
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);
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type Call_Modes is
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(Simple_Call, Conditional_Call, Asynchronous_Call, Timed_Call);
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type Select_Modes is (Simple_Mode, Else_Mode, Terminate_Mode, Delay_Mode);
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subtype Delay_Modes is Integer;
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-------------------------------
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-- Entry related definitions --
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-------------------------------
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Null_Entry : constant := 0;
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Max_Entry : constant := Integer'Last;
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Interrupt_Entry : constant := -2;
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Cancelled_Entry : constant := -1;
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type Entry_Index is range Interrupt_Entry .. Max_Entry;
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Null_Task_Entry : constant := Null_Entry;
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Max_Task_Entry : constant := Max_Entry;
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type Task_Entry_Index is new Entry_Index
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range Null_Task_Entry .. Max_Task_Entry;
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type Entry_Call_Record;
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type Entry_Call_Link is access all Entry_Call_Record;
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type Entry_Queue is record
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Head : Entry_Call_Link;
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Tail : Entry_Call_Link;
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end record;
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type Task_Entry_Queue_Array is
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array (Task_Entry_Index range <>) of Entry_Queue;
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-- A data structure which contains the string names of entries and entry
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-- family members.
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type String_Access is access all String;
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----------------------------------
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-- Entry_Call_Record definition --
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----------------------------------
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type Entry_Call_State is
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(Never_Abortable,
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-- the call is not abortable, and never can be
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Not_Yet_Abortable,
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-- the call is not abortable, but may become so
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Was_Abortable,
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-- the call is not abortable, but once was
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Now_Abortable,
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-- the call is abortable
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Done,
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-- the call has been completed
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Cancelled
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-- the call was asynchronous, and was cancelled
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);
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pragma Ordered (Entry_Call_State);
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-- Never_Abortable is used for calls that are made in a abort deferred
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-- region (see ARM 9.8(5-11), 9.8 (20)). Such a call is never abortable.
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-- The Was_ vs. Not_Yet_ distinction is needed to decide whether it is OK
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-- to advance into the abortable part of an async. select stmt. That is
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-- allowed iff the mode is Now_ or Was_.
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-- Done indicates the call has been completed, without cancellation, or no
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-- call has been made yet at this ATC nesting level, and so aborting the
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-- call is no longer an issue. Completion of the call does not necessarily
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-- indicate "success"; the call may be returning an exception if
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-- Exception_To_Raise is non-null.
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-- Cancelled indicates the call was cancelled, and so aborting the call is
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-- no longer an issue.
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-- The call is on an entry queue unless State >= Done, in which case it may
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-- or may not be still Onqueue.
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-- Please do not modify the order of the values, without checking all uses
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-- of this type. We rely on partial "monotonicity" of
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-- Entry_Call_Record.State to avoid locking when we access this value for
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-- certain tests. In particular:
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-- 1) Once State >= Done, we can rely that the call has been
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-- completed. If State >= Done, it will not
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-- change until the task does another entry call at this level.
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-- 2) Once State >= Was_Abortable, we can rely that the call has
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-- been queued abortably at least once, and so the check for
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-- whether it is OK to advance to the abortable part of an
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-- async. select statement does not need to lock anything.
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type Restricted_Entry_Call_Record is record
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Self : Task_Id;
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-- ID of the caller
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Mode : Call_Modes;
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State : Entry_Call_State;
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pragma Atomic (State);
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-- Indicates part of the state of the call.
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--
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-- Protection: If the call is not on a queue, it should only be
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-- accessed by Self, and Self does not need any lock to modify this
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-- field.
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--
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-- Once the call is on a queue, the value should be something other
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-- than Done unless it is cancelled, and access is controller by the
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-- "server" of the queue -- i.e., the lock of Checked_To_Protection
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-- (Call_Target) if the call record is on the queue of a PO, or the
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-- lock of Called_Target if the call is on the queue of a task. See
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-- comments on type declaration for more details.
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Uninterpreted_Data : System.Address;
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-- Data passed by the compiler
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Exception_To_Raise : Ada.Exceptions.Exception_Id;
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-- The exception to raise once this call has been completed without
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-- being aborted.
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end record;
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pragma Suppress_Initialization (Restricted_Entry_Call_Record);
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-------------------------------------------
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-- Task termination procedure definition --
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-------------------------------------------
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-- We need to redefine here these types (already defined in
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-- Ada.Task_Termination) for avoiding circular dependencies.
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type Cause_Of_Termination is (Normal, Abnormal, Unhandled_Exception);
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-- Possible causes for task termination:
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--
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-- Normal means that the task terminates due to completing the
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-- last sentence of its body, or as a result of waiting on a
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-- terminate alternative.
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-- Abnormal means that the task terminates because it is being aborted
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-- handled_Exception means that the task terminates because of exception
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-- raised by the execution of its task_body.
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type Termination_Handler is access protected procedure
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(Cause : Cause_Of_Termination;
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T : Task_Id;
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X : Ada.Exceptions.Exception_Occurrence);
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-- Used to represent protected procedures to be executed when task
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-- terminates.
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type Initialization_Handler is access procedure;
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pragma Favor_Top_Level (Initialization_Handler);
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-- Use to represent procedures to be executed at task initialization.
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Global_Initialization_Handler : Initialization_Handler := null;
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pragma Atomic (Global_Initialization_Handler);
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-- Global handler called when each task initializes.
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------------------------------------
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-- Dispatching domain definitions --
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------------------------------------
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-- We need to redefine here these types (already defined in
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-- System.Multiprocessor.Dispatching_Domains) for avoiding circular
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-- dependencies.
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type Dispatching_Domain is
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array (System.Multiprocessors.CPU range <>) of Boolean;
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-- A dispatching domain needs to contain the set of processors belonging
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-- to it. This is a processor mask where a True indicates that the
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-- processor belongs to the dispatching domain.
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-- Do not use the full range of CPU_Range because it would create a very
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-- long array. This way we can use the exact range of processors available
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-- in the system.
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type Dispatching_Domain_Access is access Dispatching_Domain;
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System_Domain : Dispatching_Domain_Access;
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-- All processors belong to default system dispatching domain at start up.
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-- We use a pointer which creates the actual variable for the reasons
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-- explained bellow in Dispatching_Domain_Tasks.
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Dispatching_Domains_Frozen : Boolean := False;
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-- True when the main procedure has been called. Hence, no new dispatching
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-- domains can be created when this flag is True.
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type Array_Allocated_Tasks is
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array (System.Multiprocessors.CPU range <>) of Natural;
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-- At start-up time, we need to store the number of tasks attached to
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-- concrete processors within the system domain (we can only create
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-- dispatching domains with processors belonging to the system domain and
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-- without tasks allocated).
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type Array_Allocated_Tasks_Access is access Array_Allocated_Tasks;
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Dispatching_Domain_Tasks : Array_Allocated_Tasks_Access;
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-- We need to store whether there are tasks allocated to concrete
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-- processors in the default system dispatching domain because we need to
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-- check it before creating a new dispatching domain. Two comments about
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-- why we use a pointer here and not in package Dispatching_Domains:
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--
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-- 1) We use an array created dynamically in procedure Initialize which
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-- is called at the beginning of the initialization of the run-time
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-- library. Declaring a static array here in the spec would not work
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-- across different installations because it would get the value of
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-- Number_Of_CPUs from the machine where the run-time library is built,
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-- and not from the machine where the application is executed. That is
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-- the reason why we create the array (CPU'First .. Number_Of_CPUs) at
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-- execution time in the procedure body, ensuring that the function
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-- Number_Of_CPUs is executed at execution time (the same trick as we
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-- use for System_Domain).
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--
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-- 2) We have moved this declaration from package Dispatching_Domains
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-- because when we use a pragma CPU, the affinity is passed through the
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-- call to Create_Task. Hence, at this point, we may need to update the
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-- number of tasks associated to the processor, but we do not want to
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-- force a dependency from this package on Dispatching_Domains.
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------------------------------------
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-- Task related other definitions --
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------------------------------------
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type Activation_Chain is limited private;
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-- Linked list of to-be-activated tasks, linked through
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-- Activation_Link. The order of tasks on the list is irrelevant, because
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-- the priority rules will ensure that they actually start activating in
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-- priority order.
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type Activation_Chain_Access is access all Activation_Chain;
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type Task_Procedure_Access is access procedure (Arg : System.Address);
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type Access_Boolean is access all Boolean;
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function Detect_Blocking return Boolean;
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pragma Inline (Detect_Blocking);
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-- Return whether the Detect_Blocking pragma is enabled
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function Storage_Size (T : Task_Id) return System.Parameters.Size_Type;
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-- Retrieve from the TCB of the task the allocated size of its stack,
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-- either the system default or the size specified by a pragma. This is in
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-- general a non-static value that can depend on discriminants of the task.
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type Bit_Array is array (Integer range <>) of Boolean;
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pragma Pack (Bit_Array);
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subtype Debug_Event_Array is Bit_Array (1 .. 16);
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Global_Task_Debug_Event_Set : Boolean := False;
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-- Set True when running under debugger control and a task debug event
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-- signal has been requested.
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----------------------------------------------
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-- Ada_Task_Control_Block (ATCB) definition --
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----------------------------------------------
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-- Notes on protection (synchronization) of TRTS data structures
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-- Any field of the TCB can be written by the activator of a task when the
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-- task is created, since no other task can access the new task's
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-- state until creation is complete.
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-- The protection for each field is described in a comment starting with
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-- "Protection:".
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-- When a lock is used to protect an ATCB field, this lock is simply named
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-- Some protection is described in terms of tasks related to the
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-- ATCB being protected. These are:
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-- Self: The task which is controlled by this ATCB
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-- Acceptor: A task accepting a call from Self
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-- Caller: A task calling an entry of Self
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-- Parent: The task executing the master on which Self depends
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-- Dependent: A task dependent on Self
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-- Activator: The task that created Self and initiated its activation
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-- Created: A task created and activated by Self
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-- Note: The order of the fields is important to implement efficiently
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-- tasking support under gdb.
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-- Currently gdb relies on the order of the State, Parent, Base_Priority,
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-- Task_Image, Task_Image_Len, Call and LL fields.
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|
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-------------------------
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-- Common ATCB section --
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-------------------------
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-- Section used by all GNARL implementations (regular and restricted)
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type Common_ATCB is limited record
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State : Task_States;
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pragma Atomic (State);
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-- Encodes some basic information about the state of a task,
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-- including whether it has been activated, whether it is sleeping,
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-- and whether it is terminated.
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--
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-- Protection: Self.L
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Parent : Task_Id;
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-- The task on which this task depends.
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-- See also Master_Level and Master_Within.
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Base_Priority : System.Any_Priority;
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-- Base priority, not changed during entry calls, only changed
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-- via dynamic priorities package.
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--
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-- Protection: Only written by Self, accessed by anyone
|
|
|
|
Base_CPU : System.Multiprocessors.CPU_Range;
|
|
-- Base CPU, only changed via dispatching domains package.
|
|
--
|
|
-- Protection: Self.L
|
|
|
|
Current_Priority : System.Any_Priority;
|
|
-- Active priority, except that the effects of protected object
|
|
-- priority ceilings are not reflected. This only reflects explicit
|
|
-- priority changes and priority inherited through task activation
|
|
-- and rendezvous.
|
|
--
|
|
-- Ada 95 notes: In Ada 95, this field will be transferred to the
|
|
-- Priority field of an Entry_Calls component when an entry call is
|
|
-- initiated. The Priority of the Entry_Calls component will not change
|
|
-- for the duration of the call. The accepting task can use it to boost
|
|
-- its own priority without fear of its changing in the meantime.
|
|
--
|
|
-- This can safely be used in the priority ordering of entry queues.
|
|
-- Once a call is queued, its priority does not change.
|
|
--
|
|
-- Since an entry call cannot be made while executing a protected
|
|
-- action, the priority of a task will never reflect a priority ceiling
|
|
-- change at the point of an entry call.
|
|
--
|
|
-- Protection: Only written by Self, and only accessed when Acceptor
|
|
-- accepts an entry or when Created activates, at which points Self is
|
|
-- suspended.
|
|
|
|
Protected_Action_Nesting : Natural;
|
|
pragma Atomic (Protected_Action_Nesting);
|
|
-- The dynamic level of protected action nesting for this task. This
|
|
-- field is needed for checking whether potentially blocking operations
|
|
-- are invoked from protected actions. pragma Atomic is used because it
|
|
-- can be read/written from protected interrupt handlers.
|
|
|
|
Task_Image : String (1 .. System.Parameters.Max_Task_Image_Length);
|
|
-- Hold a string that provides a readable id for task, built from the
|
|
-- variable of which it is a value or component.
|
|
|
|
Task_Image_Len : Natural;
|
|
-- Actual length of Task_Image
|
|
|
|
Call : Entry_Call_Link;
|
|
-- The entry call that has been accepted by this task.
|
|
--
|
|
-- Protection: Self.L. Self will modify this field when Self.Accepting
|
|
-- is False, and will not need the mutex to do so. Once a task sets
|
|
-- Pending_ATC_Level = Level_Completed_Task, no other task can access
|
|
-- this field.
|
|
|
|
LL : aliased Task_Primitives.Private_Data;
|
|
-- Control block used by the underlying low-level tasking service
|
|
-- (GNULLI).
|
|
--
|
|
-- Protection: This is used only by the GNULLI implementation, which
|
|
-- takes care of all of its synchronization.
|
|
|
|
Task_Arg : System.Address;
|
|
-- The argument to task procedure. Provide a handle for discriminant
|
|
-- information.
|
|
--
|
|
-- Protection: Part of the synchronization between Self and Activator.
|
|
-- Activator writes it, once, before Self starts executing. Thereafter,
|
|
-- Self only reads it.
|
|
|
|
Task_Alternate_Stack : System.Address;
|
|
-- The address of the alternate signal stack for this task, if any
|
|
--
|
|
-- Protection: Only accessed by Self
|
|
|
|
Task_Entry_Point : Task_Procedure_Access;
|
|
-- Information needed to call the procedure containing the code for
|
|
-- the body of this task.
|
|
--
|
|
-- Protection: Part of the synchronization between Self and Activator.
|
|
-- Activator writes it, once, before Self starts executing. Self reads
|
|
-- it, once, as part of its execution.
|
|
|
|
Compiler_Data : System.Soft_Links.TSD;
|
|
-- Task-specific data needed by the compiler to store per-task
|
|
-- structures.
|
|
--
|
|
-- Protection: Only accessed by Self
|
|
|
|
All_Tasks_Link : Task_Id;
|
|
-- Used to link this task to the list of all tasks in the system
|
|
--
|
|
-- Protection: RTS_Lock
|
|
|
|
Activation_Link : Task_Id;
|
|
-- Used to link this task to a list of tasks to be activated
|
|
--
|
|
-- Protection: Only used by Activator
|
|
|
|
Activator : Task_Id;
|
|
pragma Atomic (Activator);
|
|
-- The task that created this task, either by declaring it as a task
|
|
-- object or by executing a task allocator. The value is null iff Self
|
|
-- has completed activation.
|
|
--
|
|
-- Protection: Set by Activator before Self is activated, and
|
|
-- only modified by Self after that. Can be read by any task via
|
|
-- Ada.Task_Identification.Activation_Is_Complete; hence Atomic.
|
|
|
|
Wait_Count : Natural;
|
|
-- This count is used by a task that is waiting for other tasks. At all
|
|
-- other times, the value should be zero. It is used differently in
|
|
-- several different states. Since a task cannot be in more than one of
|
|
-- these states at the same time, a single counter suffices.
|
|
--
|
|
-- Protection: Self.L
|
|
|
|
-- Activator_Sleep
|
|
|
|
-- This is the number of tasks that this task is activating, i.e. the
|
|
-- children that have started activation but have not completed it.
|
|
--
|
|
-- Protection: Self.L and Created.L. Both mutexes must be locked, since
|
|
-- Self.Activation_Count and Created.State must be synchronized.
|
|
|
|
-- Master_Completion_Sleep (phase 1)
|
|
|
|
-- This is the number dependent tasks of a master being completed by
|
|
-- Self that are activated, but have not yet terminated, and are not
|
|
-- waiting on a terminate alternative.
|
|
|
|
-- Master_Completion_2_Sleep (phase 2)
|
|
|
|
-- This is the count of tasks dependent on a master being completed by
|
|
-- Self which are waiting on a terminate alternative.
|
|
|
|
Elaborated : Access_Boolean;
|
|
-- Pointer to a flag indicating that this task's body has been
|
|
-- elaborated. The flag is created and managed by the
|
|
-- compiler-generated code.
|
|
--
|
|
-- Protection: The field itself is only accessed by Activator. The flag
|
|
-- that it points to is updated by Master and read by Activator; access
|
|
-- is assumed to be atomic.
|
|
|
|
Activation_Failed : Boolean;
|
|
-- Set to True if activation of a chain of tasks fails,
|
|
-- so that the activator should raise Tasking_Error.
|
|
|
|
Task_Info : System.Task_Info.Task_Info_Type;
|
|
-- System-specific attributes of the task as specified by the
|
|
-- Task_Info pragma.
|
|
|
|
Analyzer : System.Stack_Usage.Stack_Analyzer;
|
|
-- For storing information used to measure the stack usage
|
|
|
|
Global_Task_Lock_Nesting : Natural;
|
|
-- This is the current nesting level of calls to
|
|
-- System.Tasking.Initialization.Lock_Task. This allows a task to call
|
|
-- Lock_Task multiple times without deadlocking. A task only locks
|
|
-- Global_Task_Lock when its Global_Task_Lock_Nesting goes from 0 to 1,
|
|
-- and only unlocked when it goes from 1 to 0.
|
|
--
|
|
-- Protection: Only accessed by Self
|
|
|
|
Fall_Back_Handler : Termination_Handler;
|
|
-- This is the fall-back handler that applies to the dependent tasks of
|
|
-- the task.
|
|
--
|
|
-- Protection: Self.L
|
|
|
|
Specific_Handler : Termination_Handler;
|
|
-- This is the specific handler that applies only to this task, and not
|
|
-- any of its dependent tasks.
|
|
--
|
|
-- Protection: Self.L
|
|
|
|
Debug_Events : Debug_Event_Array;
|
|
-- Word length array of per task debug events, of which 11 kinds are
|
|
-- currently defined in System.Tasking.Debugging package.
|
|
|
|
Domain : Dispatching_Domain_Access;
|
|
-- Domain is the dispatching domain to which the task belongs. It is
|
|
-- only changed via dispatching domains package. This field is made
|
|
-- part of the Common_ATCB, even when restricted run-times (namely
|
|
-- Ravenscar) do not use it, because this way the field is always
|
|
-- available to the underlying layers to set the affinity and we do not
|
|
-- need to do different things depending on the situation.
|
|
--
|
|
-- Protection: Self.L
|
|
end record;
|
|
|
|
---------------------------------------
|
|
-- Restricted_Ada_Task_Control_Block --
|
|
---------------------------------------
|
|
|
|
-- This type should only be used by the restricted GNARLI and by restricted
|
|
-- GNULL implementations to allocate an ATCB (see System.Task_Primitives.
|
|
-- Operations.New_ATCB) that will take significantly less memory.
|
|
|
|
-- Note that the restricted GNARLI should only access fields that are
|
|
-- present in the Restricted_Ada_Task_Control_Block structure.
|
|
|
|
type Restricted_Ada_Task_Control_Block (Entry_Num : Task_Entry_Index) is
|
|
limited record
|
|
Common : Common_ATCB;
|
|
-- The common part between various tasking implementations
|
|
|
|
Entry_Call : aliased Restricted_Entry_Call_Record;
|
|
-- Protection: This field is used on entry call "queues" associated
|
|
-- with protected objects, and is protected by the protected object
|
|
-- lock.
|
|
end record;
|
|
pragma Suppress_Initialization (Restricted_Ada_Task_Control_Block);
|
|
|
|
Interrupt_Manager_ID : Task_Id;
|
|
-- This task ID is declared here to break circular dependencies.
|
|
-- Also declare Interrupt_Manager_ID after Task_Id is known, to avoid
|
|
-- generating unneeded finalization code.
|
|
|
|
-----------------------
|
|
-- List of all Tasks --
|
|
-----------------------
|
|
|
|
All_Tasks_List : Task_Id;
|
|
-- Global linked list of all tasks
|
|
|
|
------------------------------------------
|
|
-- Regular (non restricted) definitions --
|
|
------------------------------------------
|
|
|
|
--------------------------------
|
|
-- Master Related Definitions --
|
|
--------------------------------
|
|
|
|
subtype Master_Level is Integer;
|
|
subtype Master_ID is Master_Level;
|
|
|
|
-- Normally, a task starts out with internal master nesting level one
|
|
-- larger than external master nesting level. It is incremented by one by
|
|
-- Enter_Master, which is called in the task body only if the compiler
|
|
-- thinks the task may have dependent tasks. It is set to 1 for the
|
|
-- environment task, the level 2 is reserved for server tasks of the
|
|
-- run-time system (the so called "independent tasks"), and the level 3 is
|
|
-- for the library level tasks. Foreign threads which are detected by
|
|
-- the run-time have a level of 0, allowing these tasks to be easily
|
|
-- distinguished if needed.
|
|
|
|
Foreign_Task_Level : constant Master_Level := 0;
|
|
Environment_Task_Level : constant Master_Level := 1;
|
|
Independent_Task_Level : constant Master_Level := 2;
|
|
Library_Task_Level : constant Master_Level := 3;
|
|
|
|
-------------------
|
|
-- Priority info --
|
|
-------------------
|
|
|
|
Unspecified_Priority : constant Integer := System.Priority'First - 1;
|
|
|
|
Priority_Not_Boosted : constant Integer := System.Priority'First - 1;
|
|
-- Definition of Priority actually has to come from the RTS configuration
|
|
|
|
subtype Rendezvous_Priority is Integer
|
|
range Priority_Not_Boosted .. System.Any_Priority'Last;
|
|
|
|
-------------------
|
|
-- Affinity info --
|
|
-------------------
|
|
|
|
Unspecified_CPU : constant := -1;
|
|
-- No affinity specified
|
|
|
|
------------------------------------
|
|
-- Rendezvous related definitions --
|
|
------------------------------------
|
|
|
|
No_Rendezvous : constant := 0;
|
|
|
|
Max_Select : constant Integer := Integer'Last;
|
|
-- RTS-defined
|
|
|
|
subtype Select_Index is Integer range No_Rendezvous .. Max_Select;
|
|
-- type Select_Index is range No_Rendezvous .. Max_Select;
|
|
|
|
subtype Positive_Select_Index is
|
|
Select_Index range 1 .. Select_Index'Last;
|
|
|
|
type Accept_Alternative is record
|
|
Null_Body : Boolean;
|
|
S : Task_Entry_Index;
|
|
end record;
|
|
|
|
type Accept_List is
|
|
array (Positive_Select_Index range <>) of Accept_Alternative;
|
|
|
|
type Accept_List_Access is access constant Accept_List;
|
|
|
|
-----------------------------------
|
|
-- ATC_Level related definitions --
|
|
-----------------------------------
|
|
|
|
Max_ATC_Nesting : constant Natural := 20;
|
|
-- The maximum number of nested asynchronous select statements supported
|
|
-- by the runtime.
|
|
|
|
subtype ATC_Level_Base is Integer range -1 .. Max_ATC_Nesting;
|
|
-- Indicates the number of nested asynchronous task control statements
|
|
-- or entries a task is in.
|
|
|
|
Level_Completed_Task : constant ATC_Level_Base := -1;
|
|
-- ATC_Level of a task that has "completed". A task reaches the completed
|
|
-- state after an abort, exception propagation, or normal exit.
|
|
|
|
Level_No_ATC_Occurring : constant ATC_Level_Base := 0;
|
|
-- ATC_Level of a task not executing a entry call or an asynchronous
|
|
-- select statement.
|
|
|
|
Level_No_Pending_Abort : constant ATC_Level_Base := ATC_Level_Base'Last;
|
|
-- ATC_Level when there is no pending abort
|
|
|
|
subtype ATC_Level is ATC_Level_Base range
|
|
Level_No_ATC_Occurring .. Level_No_Pending_Abort - 1;
|
|
-- Nested ATC_Levels valid during the execution of a task
|
|
|
|
subtype ATC_Level_Index is ATC_Level range
|
|
Level_No_ATC_Occurring + 1 .. ATC_Level'Last;
|
|
-- ATC_Levels valid when a task is executing an entry call or asynchronous
|
|
-- task control statements.
|
|
|
|
----------------------------------
|
|
-- Entry_Call_Record definition --
|
|
----------------------------------
|
|
|
|
type Entry_Call_Record is record
|
|
Self : Task_Id;
|
|
-- ID of the caller
|
|
|
|
Mode : Call_Modes;
|
|
|
|
State : Entry_Call_State;
|
|
pragma Atomic (State);
|
|
-- Indicates part of the state of the call
|
|
--
|
|
-- Protection: If the call is not on a queue, it should only be
|
|
-- accessed by Self, and Self does not need any lock to modify this
|
|
-- field. Once the call is on a queue, the value should be something
|
|
-- other than Done unless it is cancelled, and access is controller by
|
|
-- the "server" of the queue -- i.e., the lock of Checked_To_Protection
|
|
-- (Call_Target) if the call record is on the queue of a PO, or the
|
|
-- lock of Called_Target if the call is on the queue of a task. See
|
|
-- comments on type declaration for more details.
|
|
|
|
Uninterpreted_Data : System.Address;
|
|
-- Data passed by the compiler
|
|
|
|
Exception_To_Raise : Ada.Exceptions.Exception_Id;
|
|
-- The exception to raise once this call has been completed without
|
|
-- being aborted.
|
|
|
|
Prev : Entry_Call_Link;
|
|
|
|
Next : Entry_Call_Link;
|
|
|
|
Level : ATC_Level;
|
|
-- One of Self and Level are redundant in this implementation, since
|
|
-- each Entry_Call_Record is at Self.Entry_Calls (Level). Since we must
|
|
-- have access to the entry call record to be reading this, we could
|
|
-- get Self from Level, or Level from Self. However, this requires
|
|
-- non-portable address arithmetic.
|
|
|
|
E : Entry_Index;
|
|
|
|
Prio : System.Any_Priority;
|
|
|
|
-- The above fields are those that there may be some hope of packing.
|
|
-- They are gathered together to allow for compilers that lay records
|
|
-- out contiguously, to allow for such packing.
|
|
|
|
Called_Task : Task_Id;
|
|
pragma Atomic (Called_Task);
|
|
-- Use for task entry calls. The value is null if the call record is
|
|
-- not in use. Conversely, unless State is Done and Onqueue is false,
|
|
-- Called_Task points to an ATCB.
|
|
--
|
|
-- Protection: Called_Task.L
|
|
|
|
Called_PO : System.Address;
|
|
pragma Atomic (Called_PO);
|
|
-- Similar to Called_Task but for protected objects
|
|
--
|
|
-- Note that the previous implementation tried to merge both
|
|
-- Called_Task and Called_PO but this ended up in many unexpected
|
|
-- complications (e.g having to add a magic number in the ATCB, which
|
|
-- caused gdb lots of confusion) with no real gain since the
|
|
-- Lock_Server implementation still need to loop around chasing for
|
|
-- pointer changes even with a single pointer.
|
|
|
|
Acceptor_Prev_Call : Entry_Call_Link;
|
|
-- For task entry calls only
|
|
|
|
Acceptor_Prev_Priority : Rendezvous_Priority := Priority_Not_Boosted;
|
|
-- For task entry calls only. The priority of the most recent prior
|
|
-- call being serviced. For protected entry calls, this function should
|
|
-- be performed by GNULLI ceiling locking.
|
|
|
|
Cancellation_Attempted : Boolean := False;
|
|
pragma Atomic (Cancellation_Attempted);
|
|
-- Cancellation of the call has been attempted.
|
|
-- Consider merging this into State???
|
|
|
|
With_Abort : Boolean := False;
|
|
-- Tell caller whether the call may be aborted
|
|
-- ??? consider merging this with Was_Abortable state
|
|
|
|
Needs_Requeue : Boolean := False;
|
|
-- Temporary to tell acceptor of task entry call that
|
|
-- Exceptional_Complete_Rendezvous needs to do requeue.
|
|
end record;
|
|
|
|
------------------------------------
|
|
-- Task related other definitions --
|
|
------------------------------------
|
|
|
|
type Access_Address is access all System.Address;
|
|
-- Anonymous pointer used to implement task attributes (see s-tataat.adb
|
|
-- and a-tasatt.adb)
|
|
|
|
pragma No_Strict_Aliasing (Access_Address);
|
|
-- This type is used in contexts where aliasing may be an issue (see
|
|
-- for example s-tataat.adb), so we avoid any incorrect aliasing
|
|
-- assumptions.
|
|
|
|
----------------------------------------------
|
|
-- Ada_Task_Control_Block (ATCB) definition --
|
|
----------------------------------------------
|
|
|
|
type Entry_Call_Array is array (ATC_Level_Index) of
|
|
aliased Entry_Call_Record;
|
|
|
|
type Atomic_Address is mod Memory_Size;
|
|
pragma Atomic (Atomic_Address);
|
|
type Attribute_Array is
|
|
array (1 .. Parameters.Max_Attribute_Count) of Atomic_Address;
|
|
-- Array of task attributes. The value (Atomic_Address) will either be
|
|
-- converted to a task attribute if it fits, or to a pointer to a record
|
|
-- by Ada.Task_Attributes.
|
|
|
|
type Task_Serial_Number is mod 2 ** Long_Long_Integer'Size;
|
|
-- Used to give each task a unique serial number. We want 64-bits for this
|
|
-- type to get as much uniqueness as possible (2**64 is operationally
|
|
-- infinite in this context, but 2**32 perhaps could recycle). We use
|
|
-- Long_Long_Integer (which in the normal case is always 64-bits) rather
|
|
-- than 64-bits explicitly to allow codepeer to analyze this unit when
|
|
-- a target configuration file forces the maximum integer size to 32.
|
|
|
|
type Ada_Task_Control_Block (Entry_Num : Task_Entry_Index) is limited record
|
|
Common : Common_ATCB;
|
|
-- The common part between various tasking implementations
|
|
|
|
Entry_Calls : Entry_Call_Array;
|
|
-- An array of entry calls
|
|
--
|
|
-- Protection: The elements of this array are on entry call queues
|
|
-- associated with protected objects or task entries, and are protected
|
|
-- by the protected object lock or Acceptor.L, respectively.
|
|
|
|
New_Base_Priority : System.Any_Priority;
|
|
-- New value for Base_Priority (for dynamic priorities package)
|
|
--
|
|
-- Protection: Self.L
|
|
|
|
Open_Accepts : Accept_List_Access;
|
|
-- This points to the Open_Accepts array of accept alternatives passed
|
|
-- to the RTS by the compiler-generated code to Selective_Wait. It is
|
|
-- non-null iff this task is ready to accept an entry call.
|
|
--
|
|
-- Protection: Self.L
|
|
|
|
Chosen_Index : Select_Index;
|
|
-- The index in Open_Accepts of the entry call accepted by a selective
|
|
-- wait executed by this task.
|
|
--
|
|
-- Protection: Written by both Self and Caller. Usually protected by
|
|
-- Self.L. However, once the selection is known to have been written it
|
|
-- can be accessed without protection. This happens after Self has
|
|
-- updated it itself using information from a suspended Caller, or
|
|
-- after Caller has updated it and awakened Self.
|
|
|
|
Master_Of_Task : Master_Level;
|
|
-- The task executing the master of this task, and the ID of this task's
|
|
-- master (unique only among masters currently active within Parent).
|
|
--
|
|
-- Protection: Set by Activator before Self is activated, and read
|
|
-- after Self is activated.
|
|
|
|
Master_Within : Master_Level;
|
|
-- The ID of the master currently executing within this task; that is,
|
|
-- the most deeply nested currently active master.
|
|
--
|
|
-- Protection: Only written by Self, and only read by Self or by
|
|
-- dependents when Self is attempting to exit a master. Since Self will
|
|
-- not write this field until the master is complete, the
|
|
-- synchronization should be adequate to prevent races.
|
|
|
|
Alive_Count : Natural := 0;
|
|
-- Number of tasks directly dependent on this task (including itself)
|
|
-- that are still "alive", i.e. not terminated.
|
|
--
|
|
-- Protection: Self.L
|
|
|
|
Awake_Count : Natural := 0;
|
|
-- Number of tasks directly dependent on this task (including itself)
|
|
-- still "awake", i.e., are not terminated and not waiting on a
|
|
-- terminate alternative.
|
|
--
|
|
-- Invariant: Awake_Count <= Alive_Count
|
|
|
|
-- Protection: Self.L
|
|
|
|
-- Beginning of flags
|
|
|
|
Aborting : Boolean := False;
|
|
pragma Atomic (Aborting);
|
|
-- Self is in the process of aborting. While set, prevents multiple
|
|
-- abort signals from being sent by different aborter while abort
|
|
-- is acted upon. This is essential since an aborter which calls
|
|
-- Abort_To_Level could set the Pending_ATC_Level to yet a lower level
|
|
-- (than the current level), may be preempted and would send the
|
|
-- abort signal when resuming execution. At this point, the abortee
|
|
-- may have completed abort to the proper level such that the
|
|
-- signal (and resulting abort exception) are not handled any more.
|
|
-- In other words, the flag prevents a race between multiple aborters
|
|
--
|
|
-- Protection: protected by atomic access.
|
|
|
|
ATC_Hack : Boolean := False;
|
|
pragma Atomic (ATC_Hack);
|
|
-- ?????
|
|
-- Temporary fix, to allow Undefer_Abort to reset Aborting in the
|
|
-- handler for Abort_Signal that encloses an async. entry call.
|
|
-- For the longer term, this should be done via code in the
|
|
-- handler itself.
|
|
|
|
Callable : Boolean := True;
|
|
-- It is OK to call entries of this task
|
|
|
|
Dependents_Aborted : Boolean := False;
|
|
-- This is set to True by whichever task takes responsibility for
|
|
-- aborting the dependents of this task.
|
|
--
|
|
-- Protection: Self.L
|
|
|
|
Interrupt_Entry : Boolean := False;
|
|
-- Indicates if one or more Interrupt Entries are attached to the task.
|
|
-- This flag is needed for cleaning up the Interrupt Entry bindings.
|
|
|
|
Pending_Action : Boolean := False;
|
|
-- Unified flag indicating some action needs to be take when abort
|
|
-- next becomes undeferred. Currently set if:
|
|
-- . Pending_Priority_Change is set
|
|
-- . Pending_ATC_Level is changed
|
|
-- . Requeue involving POs
|
|
-- (Abortable field may have changed and the Wait_Until_Abortable
|
|
-- has to recheck the abortable status of the call.)
|
|
-- . Exception_To_Raise is non-null
|
|
--
|
|
-- Protection: Self.L
|
|
--
|
|
-- This should never be reset back to False outside of the procedure
|
|
-- Do_Pending_Action, which is called by Undefer_Abort. It should only
|
|
-- be set to True by Set_Priority and Abort_To_Level.
|
|
|
|
Pending_Priority_Change : Boolean := False;
|
|
-- Flag to indicate pending priority change (for dynamic priorities
|
|
-- package). The base priority is updated on the next abort
|
|
-- completion point (aka. synchronization point).
|
|
--
|
|
-- Protection: Self.L
|
|
|
|
Terminate_Alternative : Boolean := False;
|
|
-- Task is accepting Select with Terminate Alternative
|
|
--
|
|
-- Protection: Self.L
|
|
|
|
-- End of flags
|
|
|
|
-- Beginning of counts
|
|
|
|
ATC_Nesting_Level : ATC_Level := Level_No_ATC_Occurring;
|
|
-- The dynamic level of ATC nesting (currently executing nested
|
|
-- asynchronous select statements) in this task.
|
|
|
|
-- Protection: Self_ID.L. Only Self reads or updates this field.
|
|
-- Decrementing it deallocates an Entry_Calls component, and care must
|
|
-- be taken that all references to that component are eliminated before
|
|
-- doing the decrement. This in turn will require locking a protected
|
|
-- object (for a protected entry call) or the Acceptor's lock (for a
|
|
-- task entry call). No other task should attempt to read or modify
|
|
-- this value.
|
|
|
|
Deferral_Level : Natural := 1;
|
|
-- This is the number of times that Defer_Abort has been called by
|
|
-- this task without a matching Undefer_Abort call. Abortion is only
|
|
-- allowed when this zero. It is initially 1, to protect the task at
|
|
-- startup.
|
|
|
|
-- Protection: Only updated by Self; access assumed to be atomic
|
|
|
|
Pending_ATC_Level : ATC_Level_Base := Level_No_Pending_Abort;
|
|
-- Indicates the ATC level to which this task is currently being
|
|
-- aborted. Two special values exist:
|
|
--
|
|
-- * Level_Completed_Task: the task has completed.
|
|
--
|
|
-- * Level_No_Pending_Abort: the task is not being aborted to any
|
|
-- level.
|
|
--
|
|
-- All other values indicate the task has not completed. This should
|
|
-- ONLY be modified by Abort_To_Level and Exit_One_ATC_Level.
|
|
--
|
|
-- Protection: Self.L
|
|
|
|
Serial_Number : Task_Serial_Number;
|
|
-- Monotonic counter to provide some way to check locking rules/ordering
|
|
|
|
Known_Tasks_Index : Integer := -1;
|
|
-- Index in the System.Tasking.Debug.Known_Tasks array
|
|
|
|
User_State : Long_Integer := 0;
|
|
-- User-writeable location, for use in debugging tasks; also provides a
|
|
-- simple task specific data.
|
|
|
|
Free_On_Termination : Boolean := False;
|
|
-- Deallocate the ATCB when the task terminates. This flag is normally
|
|
-- False, and is set True when Unchecked_Deallocation is called on a
|
|
-- non-terminated task so that the associated storage is automatically
|
|
-- reclaimed when the task terminates.
|
|
|
|
Attributes : Attribute_Array := (others => 0);
|
|
-- Task attributes
|
|
|
|
-- IMPORTANT Note: the Entry_Queues field is last for efficiency of
|
|
-- access to other fields, do not put new fields after this one.
|
|
|
|
Entry_Queues : Task_Entry_Queue_Array (1 .. Entry_Num);
|
|
-- An array of task entry queues
|
|
--
|
|
-- Protection: Self.L. Once a task has set Self.Stage to Completing, it
|
|
-- has exclusive access to this field.
|
|
end record;
|
|
|
|
--------------------
|
|
-- Initialization --
|
|
--------------------
|
|
|
|
procedure Initialize;
|
|
-- This procedure constitutes the first part of the initialization of the
|
|
-- GNARL. This includes creating data structures to make the initial thread
|
|
-- into the environment task. The last part of the initialization is done
|
|
-- in System.Tasking.Initialization or System.Tasking.Restricted.Stages.
|
|
-- All the initializations used to be in Tasking.Initialization, but this
|
|
-- is no longer possible with the run time simplification (including
|
|
-- optimized PO and the restricted run time) since one cannot rely on
|
|
-- System.Tasking.Initialization being present, as was done before.
|
|
|
|
procedure Initialize_ATCB
|
|
(Self_ID : Task_Id;
|
|
Task_Entry_Point : Task_Procedure_Access;
|
|
Task_Arg : System.Address;
|
|
Parent : Task_Id;
|
|
Elaborated : Access_Boolean;
|
|
Base_Priority : System.Any_Priority;
|
|
Base_CPU : System.Multiprocessors.CPU_Range;
|
|
Domain : Dispatching_Domain_Access;
|
|
Task_Info : System.Task_Info.Task_Info_Type;
|
|
Stack_Size : System.Parameters.Size_Type;
|
|
T : Task_Id;
|
|
Success : out Boolean);
|
|
-- Initialize fields of the TCB for task T, and link into global TCB
|
|
-- structures. Call this only with abort deferred and holding RTS_Lock.
|
|
-- Self_ID is the calling task (normally the activator of T). Success is
|
|
-- set to indicate whether the TCB was successfully initialized.
|
|
|
|
private
|
|
|
|
Null_Task : constant Task_Id := null;
|
|
|
|
type Activation_Chain is limited record
|
|
T_ID : Task_Id;
|
|
end record;
|
|
|
|
-- Activation_Chain is an in-out parameter of initialization procedures and
|
|
-- it must be passed by reference because the init proc may terminate
|
|
-- abnormally after creating task components, and these must be properly
|
|
-- registered for removal (Expunge_Unactivated_Tasks). The "limited" forces
|
|
-- Activation_Chain to be a by-reference type; see RM-6.2(4).
|
|
|
|
function Number_Of_Entries (Self_Id : Task_Id) return Entry_Index;
|
|
-- Given a task, return the number of entries it contains
|
|
end System.Tasking;
|