File : s-tasren.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 . R E N D E Z V O U S --
6 -- --
7 -- S p e c --
8 -- --
9 -- Copyright (C) 1992-2012, 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 -- Note: the compiler generates direct calls to this interface, via Rtsfind.
33 -- Any changes to this interface may require corresponding compiler changes.
34
35 with Ada.Exceptions;
36
37 with System.Tasking.Protected_Objects.Entries;
38
39 package System.Tasking.Rendezvous is
40
41 package STPE renames System.Tasking.Protected_Objects.Entries;
42
43 procedure Task_Entry_Call
44 (Acceptor : Task_Id;
45 E : Task_Entry_Index;
46 Uninterpreted_Data : System.Address;
47 Mode : Call_Modes;
48 Rendezvous_Successful : out Boolean);
49 -- General entry call used to implement ATC or conditional entry calls.
50 -- Compiler interface only. Do not call from within the RTS.
51 -- Acceptor is the ID of the acceptor task.
52 -- E is the entry index requested.
53 -- Uninterpreted_Data represents the parameters of the entry. It is
54 -- constructed by the compiler for the caller and the callee; therefore,
55 -- the run time never needs to decode this data.
56 -- Mode can be either Asynchronous_Call (ATC) or Conditional_Call.
57 -- Rendezvous_Successful is set to True on return if the call was serviced.
58
59 procedure Timed_Task_Entry_Call
60 (Acceptor : Task_Id;
61 E : Task_Entry_Index;
62 Uninterpreted_Data : System.Address;
63 Timeout : Duration;
64 Mode : Delay_Modes;
65 Rendezvous_Successful : out Boolean);
66 -- Timed entry call without using ATC.
67 -- Compiler interface only. Do not call from within the RTS.
68 -- See Task_Entry_Call for details on Acceptor, E and Uninterpreted_Data.
69 -- Timeout is the value of the time out.
70 -- Mode determines whether the delay is relative or absolute.
71
72 procedure Call_Simple
73 (Acceptor : Task_Id;
74 E : Task_Entry_Index;
75 Uninterpreted_Data : System.Address);
76 -- Simple entry call.
77 -- Compiler interface only. Do not call from within the RTS.
78 --
79 -- source:
80 -- T.E1 (Params);
81 --
82 -- expansion:
83 -- declare
84 -- P : parms := (parm1, parm2, parm3);
85 -- X : Task_Entry_Index := 1;
86 -- begin
87 -- Call_Simple (t._task_id, X, P'Address);
88 -- parm1 := P.param1;
89 -- parm2 := P.param2;
90 -- ...
91 -- end;
92
93 procedure Cancel_Task_Entry_Call (Cancelled : out Boolean);
94 -- Cancel pending asynchronous task entry call.
95 -- Compiler interface only. Do not call from within the RTS.
96 -- See Exp_Ch9.Expand_N_Asynchronous_Select for code expansion.
97
98 procedure Requeue_Task_Entry
99 (Acceptor : Task_Id;
100 E : Task_Entry_Index;
101 With_Abort : Boolean);
102 -- Requeue from a task entry to a task entry.
103 -- Compiler interface only. Do not call from within the RTS.
104 -- The code generation for task entry requeues is different from that for
105 -- protected entry requeues. There is a "goto" that skips around the call
106 -- to Complete_Rendezvous, so that Requeue_Task_Entry must also do the work
107 -- of Complete_Rendezvous. The difference is that it does not report that
108 -- the call's State = Done.
109 --
110 -- source:
111 -- accept e1 do
112 -- ...A...
113 -- requeue e2;
114 -- ...B...
115 -- end e1;
116 --
117 -- expansion:
118 -- A62b : address;
119 -- L61b : label
120 -- begin
121 -- accept_call (1, A62b);
122 -- ...A...
123 -- requeue_task_entry (tTV!(t)._task_id, 2, false);
124 -- goto L61b;
125 -- ...B...
126 -- complete_rendezvous;
127 -- <<L61b>>
128 -- exception
129 -- when others =>
130 -- exceptional_complete_rendezvous (current_exception);
131 -- end;
132
133 procedure Requeue_Protected_To_Task_Entry
134 (Object : STPE.Protection_Entries_Access;
135 Acceptor : Task_Id;
136 E : Task_Entry_Index;
137 With_Abort : Boolean);
138 -- Requeue from a protected entry to a task entry.
139 -- Compiler interface only. Do not call from within the RTS.
140 --
141 -- source:
142 -- entry e2 when b is
143 -- begin
144 -- b := false;
145 -- ...A...
146 -- requeue t.e2;
147 -- end e2;
148 --
149 -- expansion:
150 -- procedure rPT__E14b (O : address; P : address; E :
151 -- protected_entry_index) is
152 -- type rTVP is access rTV;
153 -- freeze rTVP []
154 -- _object : rTVP := rTVP!(O);
155 -- begin
156 -- declare
157 -- rR : protection renames _object._object;
158 -- vP : integer renames _object.v;
159 -- bP : boolean renames _object.b;
160 -- begin
161 -- b := false;
162 -- ...A...
163 -- requeue_protected_to_task_entry (rR'unchecked_access, tTV!(t).
164 -- _task_id, 2, false);
165 -- return;
166 -- end;
167 -- complete_entry_body (_object._object'unchecked_access, objectF =>
168 -- 0);
169 -- return;
170 -- exception
171 -- when others =>
172 -- abort_undefer.all;
173 -- exceptional_complete_entry_body (_object._object'
174 -- unchecked_access, current_exception, objectF => 0);
175 -- return;
176 -- end rPT__E14b;
177
178 procedure Selective_Wait
179 (Open_Accepts : Accept_List_Access;
180 Select_Mode : Select_Modes;
181 Uninterpreted_Data : out System.Address;
182 Index : out Select_Index);
183 -- Implement select statement.
184 -- Compiler interface only. Do not call from within the RTS.
185 -- See comments on Accept_Call.
186 --
187 -- source:
188 -- select accept e1 do
189 -- ...A...
190 -- end e1;
191 -- ...B...
192 -- or accept e2;
193 -- ...C...
194 -- end select;
195 --
196 -- expansion:
197 -- A32b : address;
198 -- declare
199 -- A37b : T36b;
200 -- A37b (1) := (null_body => false, s => 1);
201 -- A37b (2) := (null_body => true, s => 2);
202 -- S0 : aliased T36b := accept_list'A37b;
203 -- J1 : select_index := 0;
204 -- procedure e1A is
205 -- begin
206 -- abort_undefer.all;
207 -- ...A...
208 -- <<L31b>>
209 -- complete_rendezvous;
210 -- exception
211 -- when all others =>
212 -- exceptional_complete_rendezvous (get_gnat_exception);
213 -- end e1A;
214 -- begin
215 -- selective_wait (S0'unchecked_access, simple_mode, A32b, J1);
216 -- case J1 is
217 -- when 0 =>
218 -- goto L3;
219 -- when 1 =>
220 -- e1A;
221 -- goto L1;
222 -- when 2 =>
223 -- goto L2;
224 -- when others =>
225 -- goto L3;
226 -- end case;
227 -- <<L1>>
228 -- ...B...
229 -- goto L3;
230 -- <<L2>>
231 -- ...C...
232 -- goto L3;
233 -- <<L3>>
234 -- end;
235
236 procedure Timed_Selective_Wait
237 (Open_Accepts : Accept_List_Access;
238 Select_Mode : Select_Modes;
239 Uninterpreted_Data : out System.Address;
240 Timeout : Duration;
241 Mode : Delay_Modes;
242 Index : out Select_Index);
243 -- Selective wait with timeout without using ATC.
244 -- Compiler interface only. Do not call from within the RTS.
245
246 procedure Accept_Call
247 (E : Task_Entry_Index;
248 Uninterpreted_Data : out System.Address);
249 -- Accept an entry call.
250 -- Compiler interface only. Do not call from within the RTS.
251 --
252 -- source:
253 -- accept E do ...A... end E;
254 -- expansion:
255 -- A27b : address;
256 -- L26b : label
257 -- begin
258 -- accept_call (1, A27b);
259 -- ...A...
260 -- complete_rendezvous;
261 -- <<L26b>>
262 -- exception
263 -- when all others =>
264 -- exceptional_complete_rendezvous (get_gnat_exception);
265 -- end;
266 --
267 -- The handler for Abort_Signal (*all* others) is to handle the case when
268 -- the acceptor is aborted between Accept_Call and the corresponding
269 -- Complete_Rendezvous call. We need to wake up the caller in this case.
270 --
271 -- See also Selective_Wait
272
273 procedure Accept_Trivial (E : Task_Entry_Index);
274 -- Accept an entry call that has no parameters and no body.
275 -- Compiler interface only. Do not call from within the RTS.
276 -- This should only be called when there is no accept body, or the accept
277 -- body is empty.
278 --
279 -- source:
280 -- accept E;
281 -- expansion:
282 -- accept_trivial (1);
283 --
284 -- The compiler is also able to recognize the following and
285 -- translate it the same way.
286 --
287 -- accept E do null; end E;
288
289 function Task_Count (E : Task_Entry_Index) return Natural;
290 -- Return number of tasks waiting on the entry E (of current task)
291 -- Compiler interface only. Do not call from within the RTS.
292
293 function Callable (T : Task_Id) return Boolean;
294 -- Return T'Callable
295 -- Compiler interface. Do not call from within the RTS, except for body of
296 -- Ada.Task_Identification.
297
298 type Task_Entry_Nesting_Depth is new Task_Entry_Index
299 range 0 .. Max_Task_Entry;
300
301 function Task_Entry_Caller (D : Task_Entry_Nesting_Depth) return Task_Id;
302 -- Return E'Caller. This will only work if called from within an
303 -- accept statement that is handling E, as required by the LRM (C.7.1(14)).
304 -- Compiler interface only. Do not call from within the RTS.
305
306 procedure Complete_Rendezvous;
307 -- Called by acceptor to wake up caller
308
309 procedure Exceptional_Complete_Rendezvous
310 (Ex : Ada.Exceptions.Exception_Id);
311 pragma No_Return (Exceptional_Complete_Rendezvous);
312 -- Called by acceptor to mark the end of the current rendezvous and
313 -- propagate an exception to the caller.
314
315 -- For internal use only:
316
317 function Task_Do_Or_Queue
318 (Self_ID : Task_Id;
319 Entry_Call : Entry_Call_Link) return Boolean;
320 -- Call this only with abort deferred and holding no locks, except
321 -- the global RTS lock when Single_Lock is True which must be owned.
322 -- Returns False iff the call cannot be served or queued, as is the
323 -- case if the caller is not callable; i.e., a False return value
324 -- indicates that Tasking_Error should be raised.
325 -- Either initiate the entry call, such that the accepting task is
326 -- free to execute the rendezvous, queue the call on the acceptor's
327 -- queue, or cancel the call. Conditional calls that cannot be
328 -- accepted immediately are cancelled.
329
330 end System.Tasking.Rendezvous;