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) 1992-2014, 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 for internal use by the
58   --  GNARL, to prevent such internal server tasks from preventing a partition
59   --  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