1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
|
------------------------------------------------------------------------------
-- --
-- GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS --
-- --
-- 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 --
-- --
-- $Revision: 1.1 $
-- --
-- Copyright (C) 1992-1999, 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.
-- It also contains initialization for Ada Task Control Block (ATCB) records.
package System.Tasking.Initialization is
procedure Remove_From_All_Tasks_List (T : Task_ID);
-- Remove T from All_Tasks_List.
------------------------------------------------
-- Static (Compile-Time) Configuration Flags --
------------------------------------------------
-- ?????
-- Maybe this does not belong here? Where else?
-- For now, it is here because so is Change_Base_Priority,
-- and the two are used together.
Dynamic_Priority_Support : constant Boolean := True;
-- Should we poll for pending base priority changes at every
-- abort completion point?
---------------------------------
-- 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) exceptions that need to be raised
-- 3) 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 hard 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);
procedure Task_Unlock (Self_ID : Task_ID);
-- 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;
|
