summaryrefslogtreecommitdiff
path: root/gcc/ada/s-tasuti.adb
blob: 8e818be9ce9cba557e3afbb2de670aac93940fce (plain)
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
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
------------------------------------------------------------------------------
--                                                                          --
--                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --
--                                                                          --
--              S Y S T E M . T A S K I N G . U T I L I T I E S             --
--                                                                          --
--                                  B o d y                                 --
--                                                                          --
--         Copyright (C) 1992-2009, 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 3,  or (at your option) any later ver- --
-- sion.  GNAT 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.                                     --
--                                                                          --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception,   --
-- version 3.1, as published by the Free Software Foundation.               --
--                                                                          --
-- You should have received a copy of the GNU General Public License and    --
-- a copy of the GCC Runtime Library Exception along with this program;     --
-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
-- <http://www.gnu.org/licenses/>.                                          --
--                                                                          --
-- GNARL was developed by the GNARL team at Florida State University.       --
-- Extensive contributions were provided by Ada Core Technologies, Inc.     --
--                                                                          --
------------------------------------------------------------------------------

--  This package provides RTS Internal Declarations

--  These declarations are not part of the GNARLI

pragma Polling (Off);
--  Turn off polling, we do not want ATC polling to take place during tasking
--  operations. It causes infinite loops and other problems.

with System.Tasking.Debug;
with System.Task_Primitives.Operations;
with System.Tasking.Initialization;
with System.Tasking.Queuing;
with System.Parameters;
with System.Traces.Tasking;

package body System.Tasking.Utilities is

   package STPO renames System.Task_Primitives.Operations;

   use Parameters;
   use Tasking.Debug;
   use Task_Primitives;
   use Task_Primitives.Operations;

   use System.Traces;
   use System.Traces.Tasking;

   --------------------
   -- Abort_One_Task --
   --------------------

   --  Similar to Locked_Abort_To_Level (Self_ID, T, 0), but:
   --    (1) caller should be holding no locks except RTS_Lock when Single_Lock
   --    (2) may be called for tasks that have not yet been activated
   --    (3) always aborts whole task

   procedure Abort_One_Task (Self_ID : Task_Id; T : Task_Id) is
   begin
      if Parameters.Runtime_Traces then
         Send_Trace_Info (T_Abort, Self_ID, T);
      end if;

      Write_Lock (T);

      if T.Common.State = Unactivated then
         T.Common.Activator := null;
         T.Common.State := Terminated;
         T.Callable := False;
         Cancel_Queued_Entry_Calls (T);

      elsif T.Common.State /= Terminated then
         Initialization.Locked_Abort_To_Level (Self_ID, T, 0);
      end if;

      Unlock (T);
   end Abort_One_Task;

   -----------------
   -- Abort_Tasks --
   -----------------

   --  This must be called to implement the abort statement.
   --  Much of the actual work of the abort is done by the abortee,
   --  via the Abort_Handler signal handler, and propagation of the
   --  Abort_Signal special exception.

   procedure Abort_Tasks (Tasks : Task_List) is
      Self_Id : constant Task_Id := STPO.Self;
      C       : Task_Id;
      P       : Task_Id;

   begin
      --  If pragma Detect_Blocking is active then Program_Error must be
      --  raised if this potentially blocking operation is called from a
      --  protected action.

      if System.Tasking.Detect_Blocking
        and then Self_Id.Common.Protected_Action_Nesting > 0
      then
         raise Program_Error with "potentially blocking operation";
      end if;

      Initialization.Defer_Abort_Nestable (Self_Id);

      --  ?????
      --  Really should not be nested deferral here.
      --  Patch for code generation error that defers abort before
      --  evaluating parameters of an entry call (at least, timed entry
      --  calls), and so may propagate an exception that causes abort
      --  to remain undeferred indefinitely. See C97404B. When all
      --  such bugs are fixed, this patch can be removed.

      Lock_RTS;

      for J in Tasks'Range loop
         C := Tasks (J);
         Abort_One_Task (Self_Id, C);
      end loop;

      C := All_Tasks_List;

      while C /= null loop
         if C.Pending_ATC_Level > 0 then
            P := C.Common.Parent;

            while P /= null loop
               if P.Pending_ATC_Level = 0 then
                  Abort_One_Task (Self_Id, C);
                  exit;
               end if;

               P := P.Common.Parent;
            end loop;
         end if;

         C := C.Common.All_Tasks_Link;
      end loop;

      Unlock_RTS;
      Initialization.Undefer_Abort_Nestable (Self_Id);
   end Abort_Tasks;

   -------------------------------
   -- Cancel_Queued_Entry_Calls --
   -------------------------------

   --  This should only be called by T, unless T is a terminated previously
   --  unactivated task.

   procedure Cancel_Queued_Entry_Calls (T : Task_Id) is
      Next_Entry_Call : Entry_Call_Link;
      Entry_Call      : Entry_Call_Link;
      Self_Id         : constant Task_Id := STPO.Self;

      Caller : Task_Id;
      pragma Unreferenced (Caller);
      --  Should this be removed ???

      Level : Integer;
      pragma Unreferenced (Level);
      --  Should this be removed ???

   begin
      pragma Assert (T = Self or else T.Common.State = Terminated);

      for J in 1 .. T.Entry_Num loop
         Queuing.Dequeue_Head (T.Entry_Queues (J), Entry_Call);

         while Entry_Call /= null loop

            --  Leave Entry_Call.Done = False, since this is cancelled

            Caller := Entry_Call.Self;
            Entry_Call.Exception_To_Raise := Tasking_Error'Identity;
            Queuing.Dequeue_Head (T.Entry_Queues (J), Next_Entry_Call);
            Level := Entry_Call.Level - 1;
            Unlock (T);
            Write_Lock (Entry_Call.Self);
            Initialization.Wakeup_Entry_Caller
              (Self_Id, Entry_Call, Cancelled);
            Unlock (Entry_Call.Self);
            Write_Lock (T);
            Entry_Call.State := Done;
            Entry_Call := Next_Entry_Call;
         end loop;
      end loop;
   end Cancel_Queued_Entry_Calls;

   ------------------------
   -- Exit_One_ATC_Level --
   ------------------------

   --  Call only with abort deferred and holding lock of Self_Id.
   --  This is a bit of common code for all entry calls.
   --  The effect is to exit one level of ATC nesting.

   --  If we have reached the desired ATC nesting level, reset the
   --  requested level to effective infinity, to allow further calls.
   --  In any case, reset Self_Id.Aborting, to allow re-raising of
   --  Abort_Signal.

   procedure Exit_One_ATC_Level (Self_ID : Task_Id) is
   begin
      Self_ID.ATC_Nesting_Level := Self_ID.ATC_Nesting_Level - 1;

      pragma Debug
        (Debug.Trace (Self_ID, "EOAL: exited to ATC level: " &
         ATC_Level'Image (Self_ID.ATC_Nesting_Level), 'A'));

      pragma Assert (Self_ID.ATC_Nesting_Level >= 1);

      if Self_ID.Pending_ATC_Level < ATC_Level_Infinity then
         if Self_ID.Pending_ATC_Level = Self_ID.ATC_Nesting_Level then
            Self_ID.Pending_ATC_Level := ATC_Level_Infinity;
            Self_ID.Aborting := False;
         else
            --  Force the next Undefer_Abort to re-raise Abort_Signal

            pragma Assert
             (Self_ID.Pending_ATC_Level < Self_ID.ATC_Nesting_Level);

            if Self_ID.Aborting then
               Self_ID.ATC_Hack := True;
               Self_ID.Pending_Action := True;
            end if;
         end if;
      end if;
   end Exit_One_ATC_Level;

   ----------------------
   -- Make_Independent --
   ----------------------

   procedure Make_Independent is
      Self_Id               : constant Task_Id := STPO.Self;
      Environment_Task      : constant Task_Id := STPO.Environment_Task;
      Parent                : constant Task_Id := Self_Id.Common.Parent;
      Parent_Needs_Updating : Boolean := False;
      Master_of_Task        : Integer;

   begin
      if Self_Id.Known_Tasks_Index /= -1 then
         Known_Tasks (Self_Id.Known_Tasks_Index) := null;
      end if;

      Initialization.Defer_Abort (Self_Id);

      if Single_Lock then
         Lock_RTS;
      end if;

      Write_Lock (Environment_Task);
      Write_Lock (Self_Id);

      pragma Assert (Parent = Environment_Task
        or else Self_Id.Master_of_Task = Library_Task_Level);

      Master_of_Task := Self_Id.Master_of_Task;
      Self_Id.Master_of_Task := Independent_Task_Level;

      --  The run time assumes that the parent of an independent task is the
      --  environment task.

      if Parent /= Environment_Task then

         --  We cannot lock three tasks at the same time, so defer the
         --  operations on the parent.

         Parent_Needs_Updating := True;
         Self_Id.Common.Parent := Environment_Task;
      end if;

      --  Update Independent_Task_Count that is needed for the GLADE
      --  termination rule. See also pending update in
      --  System.Tasking.Stages.Check_Independent

      Independent_Task_Count := Independent_Task_Count + 1;

      Unlock (Self_Id);

      --  Changing the parent after creation is not trivial. Do not forget
      --  to update the old parent counts, and the new parent (i.e. the
      --  Environment_Task) counts.

      if Parent_Needs_Updating then
         Write_Lock (Parent);
         Parent.Awake_Count := Parent.Awake_Count - 1;
         Parent.Alive_Count := Parent.Alive_Count - 1;
         Environment_Task.Awake_Count := Environment_Task.Awake_Count + 1;
         Environment_Task.Alive_Count := Environment_Task.Alive_Count + 1;
         Unlock (Parent);
      end if;

      --  In case the environment task is already waiting for children to
      --  complete.
      --  ??? There may be a race condition if the environment task was not in
      --  master completion sleep when this task was created, but now is

      if Environment_Task.Common.State = Master_Completion_Sleep and then
        Master_of_Task = Environment_Task.Master_Within
      then
         Environment_Task.Common.Wait_Count :=
           Environment_Task.Common.Wait_Count - 1;
      end if;

      Unlock (Environment_Task);

      if Single_Lock then
         Unlock_RTS;
      end if;

      Initialization.Undefer_Abort (Self_Id);
   end Make_Independent;

   ------------------
   -- Make_Passive --
   ------------------

   procedure Make_Passive (Self_ID : Task_Id; Task_Completed : Boolean) is
      C : Task_Id := Self_ID;
      P : Task_Id := C.Common.Parent;

      Master_Completion_Phase : Integer;

   begin
      if P /= null then
         Write_Lock (P);
      end if;

      Write_Lock (C);

      if Task_Completed then
         Self_ID.Common.State := Terminated;

         if Self_ID.Awake_Count = 0 then

            --  We are completing via a terminate alternative.
            --  Our parent should wait in Phase 2 of Complete_Master.

            Master_Completion_Phase := 2;

            pragma Assert (Task_Completed);
            pragma Assert (Self_ID.Terminate_Alternative);
            pragma Assert (Self_ID.Alive_Count = 1);

         else
            --  We are NOT on a terminate alternative.
            --  Our parent should wait in Phase 1 of Complete_Master.

            Master_Completion_Phase := 1;
            pragma Assert (Self_ID.Awake_Count >= 1);
         end if;

      --  We are accepting with a terminate alternative

      else
         if Self_ID.Open_Accepts = null then

            --  Somebody started a rendezvous while we had our lock open.
            --  Skip the terminate alternative.

            Unlock (C);

            if P /= null then
               Unlock (P);
            end if;

            return;
         end if;

         Self_ID.Terminate_Alternative := True;
         Master_Completion_Phase := 0;

         pragma Assert (Self_ID.Terminate_Alternative);
         pragma Assert (Self_ID.Awake_Count >= 1);
      end if;

      if Master_Completion_Phase = 2 then

         --  Since our Awake_Count is zero but our Alive_Count
         --  is nonzero, we have been accepting with a terminate
         --  alternative, and we now have been told to terminate
         --  by a completed master (in some ancestor task) that
         --  is waiting (with zero Awake_Count) in Phase 2 of
         --  Complete_Master.

         pragma Debug (Debug.Trace (Self_ID, "Make_Passive: Phase 2", 'M'));

         pragma Assert (P /= null);

         C.Alive_Count := C.Alive_Count - 1;

         if C.Alive_Count > 0 then
            Unlock (C);
            Unlock (P);
            return;
         end if;

         --  C's count just went to zero, indicating that
         --  all of C's dependents are terminated.
         --  C has a parent, P.

         loop
            --  C's count just went to zero, indicating that all of C's
            --  dependents are terminated. C has a parent, P. Notify P that
            --  C and its dependents have all terminated.

            P.Alive_Count := P.Alive_Count - 1;
            exit when P.Alive_Count > 0;
            Unlock (C);
            Unlock (P);
            C := P;
            P := C.Common.Parent;

            --  Environment task cannot have terminated yet

            pragma Assert (P /= null);

            Write_Lock (P);
            Write_Lock (C);
         end loop;

         if P.Common.State = Master_Phase_2_Sleep
           and then C.Master_of_Task = P.Master_Within
         then
            pragma Assert (P.Common.Wait_Count > 0);
            P.Common.Wait_Count := P.Common.Wait_Count - 1;

            if P.Common.Wait_Count = 0 then
               Wakeup (P, Master_Phase_2_Sleep);
            end if;
         end if;

         Unlock (C);
         Unlock (P);
         return;
      end if;

      --  We are terminating in Phase 1 or Complete_Master,
      --  or are accepting on a terminate alternative.

      C.Awake_Count := C.Awake_Count - 1;

      if Task_Completed then
         C.Alive_Count := C.Alive_Count - 1;
      end if;

      if C.Awake_Count > 0 or else P = null then
         Unlock (C);

         if P /= null then
            Unlock (P);
         end if;

         return;
      end if;

      --  C's count just went to zero, indicating that all of C's
      --  dependents are terminated or accepting with terminate alt.
      --  C has a parent, P.

      loop
         --  Notify P that C has gone passive

         if P.Awake_Count > 0 then
            P.Awake_Count := P.Awake_Count - 1;
         end if;

         if Task_Completed and then C.Alive_Count = 0 then
            P.Alive_Count := P.Alive_Count - 1;
         end if;

         exit when P.Awake_Count > 0;
         Unlock (C);
         Unlock (P);
         C := P;
         P := C.Common.Parent;

         if P = null then
            return;
         end if;

         Write_Lock (P);
         Write_Lock (C);
      end loop;

      --  P has non-passive dependents

      if P.Common.State = Master_Completion_Sleep
        and then C.Master_of_Task = P.Master_Within
      then
         pragma Debug
           (Debug.Trace
            (Self_ID, "Make_Passive: Phase 1, parent waiting", 'M'));

         --  If parent is in Master_Completion_Sleep, it
         --  cannot be on a terminate alternative, hence
         --  it cannot have Awake_Count of zero.

         pragma Assert (P.Common.Wait_Count > 0);
         P.Common.Wait_Count := P.Common.Wait_Count - 1;

         if P.Common.Wait_Count = 0 then
            Wakeup (P, Master_Completion_Sleep);
         end if;

      else
         pragma Debug
           (Debug.Trace
             (Self_ID, "Make_Passive: Phase 1, parent awake", 'M'));
         null;
      end if;

      Unlock (C);
      Unlock (P);
   end Make_Passive;

end System.Tasking.Utilities;