1------------------------------------------------------------------------------ 2-- -- 3-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS -- 4-- -- 5-- S Y S T E M . T A S K I N G . U T I L I T I E S -- 6-- -- 7-- S p e c -- 8-- -- 9-- Copyright (C) 1992-2018, Free Software Foundation, Inc. -- 10-- -- 11-- GNARL is free software; you can redistribute it and/or modify it under -- 12-- terms of the GNU General Public License as published by the Free Soft- -- 13-- ware Foundation; either version 3, or (at your option) any later ver- -- 14-- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- 15-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- 16-- or FITNESS FOR A PARTICULAR PURPOSE. -- 17-- -- 18-- As a special exception under Section 7 of GPL version 3, you are granted -- 19-- additional permissions described in the GCC Runtime Library Exception, -- 20-- version 3.1, as published by the Free Software Foundation. -- 21-- -- 22-- You should have received a copy of the GNU General Public License and -- 23-- a copy of the GCC Runtime Library Exception along with this program; -- 24-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- 25-- <http://www.gnu.org/licenses/>. -- 26-- -- 27-- GNARL was developed by the GNARL team at Florida State University. -- 28-- Extensive contributions were provided by Ada Core Technologies, Inc. -- 29-- -- 30------------------------------------------------------------------------------ 31 32-- This package provides RTS Internal Declarations. 33-- These declarations are not part of the GNARLI 34 35with Ada.Unchecked_Conversion; 36with System.Task_Primitives; 37 38package System.Tasking.Utilities is 39 40 function ATCB_To_Address is new 41 Ada.Unchecked_Conversion (Task_Id, System.Task_Primitives.Task_Address); 42 43 --------------------------------- 44 -- Task_Stage Related routines -- 45 --------------------------------- 46 47 function Make_Independent return Boolean; 48 -- Move the current task to the outermost level (level 2) of the master 49 -- hierarchy of the environment task. That is one level further out 50 -- than normal tasks defined in library-level packages (level 3). The 51 -- environment task will wait for level 3 tasks to terminate normally, 52 -- then it will abort all the level 2 tasks. See Finalize_Global_Tasks 53 -- procedure for more information. 54 -- 55 -- This is a dangerous operation, and should never be used on nested tasks 56 -- or tasks that depend on any objects that might be finalized earlier than 57 -- the termination of the environment task. It is primarily for internal 58 -- use by the GNARL, to prevent such internal server tasks from preventing 59 -- a partition from terminating. 60 -- 61 -- Also note that the run time assumes that the parent of an independent 62 -- task is the environment task. If this is not the case, Make_Independent 63 -- will change the task's parent. This assumption is particularly 64 -- important for master level completion and for the computation of 65 -- Independent_Task_Count. 66 -- 67 -- NOTE WELL: Make_Independent should be called before the task reaches its 68 -- "begin", like this: 69 -- 70 -- task body Some_Independent_Task is 71 -- ... 72 -- Ignore : constant Boolean := Make_Independent; 73 -- ... 74 -- begin 75 -- 76 -- The return value is meaningless; the only reason this is a function is 77 -- to get around the Ada limitation that makes a procedure call 78 -- syntactically illegal before the "begin". 79 -- 80 -- Calling it before "begin" ensures that the call completes before the 81 -- activating task can proceed. This is important for preventing race 82 -- conditions. For example, if the environment task reaches 83 -- Finalize_Global_Tasks before some task has finished Make_Independent, 84 -- the program can hang. 85 -- 86 -- Note also that if a package declares independent tasks, it should not 87 -- initialize its package-body data after "begin" of the package, because 88 -- that's where the tasks are activated. Initializing such data before the 89 -- task activation helps prevent the tasks from accessing uninitialized 90 -- data. 91 92 Independent_Task_Count : Natural := 0; 93 -- Number of independent tasks. This counter is incremented each time 94 -- Make_Independent is called. Note that if a server task terminates, 95 -- this counter will not be decremented. Since Make_Independent locks 96 -- the environment task (because every independent task depends on it), 97 -- this counter is protected by the environment task's lock. 98 99 --------------------------------- 100 -- Task Abort Related Routines -- 101 --------------------------------- 102 103 procedure Cancel_Queued_Entry_Calls (T : Task_Id); 104 -- Cancel any entry calls queued on target task. 105 -- Call this while holding T's lock (or RTS_Lock in Single_Lock mode). 106 107 procedure Exit_One_ATC_Level (Self_ID : Task_Id); 108 pragma Inline (Exit_One_ATC_Level); 109 -- Call only with abort deferred and holding lock of Self_ID. 110 -- This is a bit of common code for all entry calls. 111 -- The effect is to exit one level of ATC nesting. 112 113 procedure Abort_One_Task (Self_ID : Task_Id; T : Task_Id); 114 -- Similar to Locked_Abort_To_Level (Self_ID, T, 0), but: 115 -- (1) caller should be holding no locks 116 -- (2) may be called for tasks that have not yet been activated 117 -- (3) always aborts whole task 118 119 procedure Abort_Tasks (Tasks : Task_List); 120 -- Abort_Tasks is called to initiate abort, however, the actual 121 -- aborting is done by aborted task by means of Abort_Handler 122 123 procedure Make_Passive (Self_ID : Task_Id; Task_Completed : Boolean); 124 -- Update counts to indicate current task is either terminated or 125 -- accepting on a terminate alternative. Call holding no locks except 126 -- Global_Task_Lock when calling from Terminate_Task, and RTS_Lock when 127 -- Single_Lock is True. 128 129end System.Tasking.Utilities; 130