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
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
|
------------------------------------------------------------------------------
-- --
-- GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS --
-- --
-- S Y S T E M . T A S K _ P R I M I T I V E S . O P E R A T I O N S . --
-- S P E C I F I C --
-- --
-- B o d y --
-- --
-- --
-- Copyright (C) 1992-2001, 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 is a POSIX version of this package where foreign threads are
-- recognized.
-- Currently, DEC Unix, SCO UnixWare, Solaris pthread, HPUX pthread,
-- GNU/Linux threads and RTEMS use this version.
with System.Task_Info;
-- Use for Unspecified_Task_Info
with System.Soft_Links;
-- used to initialize TSD for a C thread, in function Self
separate (System.Task_Primitives.Operations)
package body Specific is
------------------
-- Local Data --
------------------
-- The followings are logically constants, but need to be initialized
-- at run time.
ATCB_Key : aliased pthread_key_t;
-- Key used to find the Ada Task_ID associated with a thread
-- The following are used to allow the Self function to
-- automatically generate ATCB's for C threads that happen to call
-- Ada procedure, which in turn happen to call the Ada runtime system.
type Fake_ATCB;
type Fake_ATCB_Ptr is access Fake_ATCB;
type Fake_ATCB is record
Stack_Base : Interfaces.C.unsigned := 0;
-- A value of zero indicates the node is not in use.
Next : Fake_ATCB_Ptr;
Real_ATCB : aliased Ada_Task_Control_Block (0);
end record;
Fake_ATCB_List : Fake_ATCB_Ptr;
-- A linear linked list.
-- The list is protected by Single_RTS_Lock;
-- Nodes are added to this list from the front.
-- Once a node is added to this list, it is never removed.
Fake_Task_Elaborated : aliased Boolean := True;
-- Used to identified fake tasks (i.e., non-Ada Threads).
Next_Fake_ATCB : Fake_ATCB_Ptr;
-- Used to allocate one Fake_ATCB in advance. See comment in New_Fake_ATCB
-----------------------
-- Local Subprograms --
-----------------------
---------------------------------
-- Support for New_Fake_ATCB --
---------------------------------
function New_Fake_ATCB return Task_ID;
-- Allocate and Initialize a new ATCB. This code can safely be called from
-- a foreign thread, as it doesn't access implicitly or explicitly
-- "self" before having initialized the new ATCB.
-------------------
-- New_Fake_ATCB --
-------------------
function New_Fake_ATCB return Task_ID is
Self_ID : Task_ID;
P, Q : Fake_ATCB_Ptr;
Succeeded : Boolean;
Result : Interfaces.C.int;
begin
-- This section is ticklish.
-- We dare not call anything that might require an ATCB, until
-- we have the new ATCB in place.
Lock_RTS;
Q := null;
P := Fake_ATCB_List;
while P /= null loop
if P.Stack_Base = 0 then
Q := P;
end if;
P := P.Next;
end loop;
if Q = null then
-- Create a new ATCB with zero entries.
Self_ID := Next_Fake_ATCB.Real_ATCB'Access;
Next_Fake_ATCB.Stack_Base := 1;
Next_Fake_ATCB.Next := Fake_ATCB_List;
Fake_ATCB_List := Next_Fake_ATCB;
Next_Fake_ATCB := null;
else
-- Reuse an existing fake ATCB.
Self_ID := Q.Real_ATCB'Access;
Q.Stack_Base := 1;
end if;
-- Record this as the Task_ID for the current thread.
Self_ID.Common.LL.Thread := pthread_self;
Result := pthread_setspecific (ATCB_Key, To_Address (Self_ID));
pragma Assert (Result = 0);
-- Do the standard initializations
System.Tasking.Initialize_ATCB
(Self_ID, null, Null_Address, Null_Task, Fake_Task_Elaborated'Access,
System.Priority'First, Task_Info.Unspecified_Task_Info, 0, Self_ID,
Succeeded);
pragma Assert (Succeeded);
-- Finally, it is safe to use an allocator in this thread.
if Next_Fake_ATCB = null then
Next_Fake_ATCB := new Fake_ATCB;
end if;
Self_ID.Master_of_Task := 0;
Self_ID.Master_Within := Self_ID.Master_of_Task + 1;
for L in Self_ID.Entry_Calls'Range loop
Self_ID.Entry_Calls (L).Self := Self_ID;
Self_ID.Entry_Calls (L).Level := L;
end loop;
Self_ID.Common.State := Runnable;
Self_ID.Awake_Count := 1;
-- Since this is not an ordinary Ada task, we will start out undeferred
Self_ID.Deferral_Level := 0;
System.Soft_Links.Create_TSD (Self_ID.Common.Compiler_Data);
-- ????
-- The following call is commented out to avoid dependence on
-- the System.Tasking.Initialization package.
-- It seems that if we want Ada.Task_Attributes to work correctly
-- for C threads we will need to raise the visibility of this soft
-- link to System.Soft_Links.
-- We are putting that off until this new functionality is otherwise
-- stable.
-- System.Tasking.Initialization.Initialize_Attributes_Link.all (T);
for J in Known_Tasks'Range loop
if Known_Tasks (J) = null then
Known_Tasks (J) := Self_ID;
Self_ID.Known_Tasks_Index := J;
exit;
end if;
end loop;
-- Must not unlock until Next_ATCB is again allocated.
Unlock_RTS;
return Self_ID;
end New_Fake_ATCB;
----------------
-- Initialize --
----------------
procedure Initialize (Environment_Task : Task_ID) is
Result : Interfaces.C.int;
begin
Result := pthread_key_create (ATCB_Key'Access, null);
pragma Assert (Result = 0);
Result := pthread_setspecific (ATCB_Key, To_Address (Environment_Task));
pragma Assert (Result = 0);
-- Create a free ATCB for use on the Fake_ATCB_List.
Next_Fake_ATCB := new Fake_ATCB;
end Initialize;
---------
-- Set --
---------
procedure Set (Self_Id : Task_ID) is
Result : Interfaces.C.int;
begin
Result := pthread_setspecific (ATCB_Key, To_Address (Self_Id));
pragma Assert (Result = 0);
end Set;
----------
-- Self --
----------
-- To make Ada tasks and C threads interoperate better, we have added some
-- functionality to Self. Suppose a C main program (with threads) calls an
-- Ada procedure and the Ada procedure calls the tasking runtime system.
-- Eventually, a call will be made to self. Since the call is not coming
-- from an Ada task, there will be no corresponding ATCB.
-- What we do in Self is to catch references that do not come from
-- recognized Ada tasks, and create an ATCB for the calling thread.
-- The new ATCB will be "detached" from the normal Ada task master
-- hierarchy, much like the existing implicitly created signal-server
-- tasks.
function Self return Task_ID is
Result : System.Address;
begin
Result := pthread_getspecific (ATCB_Key);
-- If the key value is Null, then it is a non-Ada task.
if Result = System.Null_Address then
return New_Fake_ATCB;
end if;
return To_Task_ID (Result);
end Self;
end Specific;
|
