File : s-tasuti.ads
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 -- --
19 -- --
20 -- --
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
35 with Ada.Unchecked_Conversion;
36 with System.Task_Primitives;
37
38 package 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
129 end System.Tasking.Utilities;