1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
5 -- S Y S T E M . T A S K I N G . U T I L I T I E S --
9 -- Copyright (C) 1992-2008, Free Software Foundation, Inc. --
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 2, or (at your option) any later ver- --
14 -- sion. GNARL 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. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNARL; see file COPYING. If not, write --
19 -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, USA. --
22 -- As a special exception, if other files instantiate generics from this --
23 -- unit, or you link this unit with other files to produce an executable, --
24 -- this unit does not by itself cause the resulting executable to be --
25 -- covered by the GNU General Public License. This exception does not --
26 -- however invalidate any other reasons why the executable file might be --
27 -- covered by the GNU Public License. --
29 -- GNARL was developed by the GNARL team at Florida State University. --
30 -- Extensive contributions were provided by Ada Core Technologies, Inc. --
32 ------------------------------------------------------------------------------
34 -- This package provides RTS Internal Declarations
36 -- These declarations are not part of the GNARLI
39 -- Turn off polling, we do not want ATC polling to take place during tasking
40 -- operations. It causes infinite loops and other problems.
42 with System.Tasking.Debug;
43 with System.Task_Primitives.Operations;
44 with System.Tasking.Initialization;
45 with System.Tasking.Queuing;
46 with System.Parameters;
47 with System.Traces.Tasking;
49 package body System.Tasking.Utilities is
51 package STPO renames System.Task_Primitives.Operations;
56 use Task_Primitives.Operations;
59 use System.Traces.Tasking;
65 -- Similar to Locked_Abort_To_Level (Self_ID, T, 0), but:
66 -- (1) caller should be holding no locks except RTS_Lock when Single_Lock
67 -- (2) may be called for tasks that have not yet been activated
68 -- (3) always aborts whole task
70 procedure Abort_One_Task (Self_ID : Task_Id; T : Task_Id) is
72 if Parameters.Runtime_Traces then
73 Send_Trace_Info (T_Abort, Self_ID, T);
78 if T.Common.State = Unactivated then
79 T.Common.Activator := null;
80 T.Common.State := Terminated;
82 Cancel_Queued_Entry_Calls (T);
84 elsif T.Common.State /= Terminated then
85 Initialization.Locked_Abort_To_Level (Self_ID, T, 0);
95 -- This must be called to implement the abort statement.
96 -- Much of the actual work of the abort is done by the abortee,
97 -- via the Abort_Handler signal handler, and propagation of the
98 -- Abort_Signal special exception.
100 procedure Abort_Tasks (Tasks : Task_List) is
101 Self_Id : constant Task_Id := STPO.Self;
106 -- If pragma Detect_Blocking is active then Program_Error must be
107 -- raised if this potentially blocking operation is called from a
110 if System.Tasking.Detect_Blocking
111 and then Self_Id.Common.Protected_Action_Nesting > 0
113 raise Program_Error with "potentially blocking operation";
116 Initialization.Defer_Abort_Nestable (Self_Id);
119 -- Really should not be nested deferral here.
120 -- Patch for code generation error that defers abort before
121 -- evaluating parameters of an entry call (at least, timed entry
122 -- calls), and so may propagate an exception that causes abort
123 -- to remain undeferred indefinitely. See C97404B. When all
124 -- such bugs are fixed, this patch can be removed.
128 for J in Tasks'Range loop
130 Abort_One_Task (Self_Id, C);
136 if C.Pending_ATC_Level > 0 then
137 P := C.Common.Parent;
140 if P.Pending_ATC_Level = 0 then
141 Abort_One_Task (Self_Id, C);
145 P := P.Common.Parent;
149 C := C.Common.All_Tasks_Link;
153 Initialization.Undefer_Abort_Nestable (Self_Id);
156 -------------------------------
157 -- Cancel_Queued_Entry_Calls --
158 -------------------------------
160 -- This should only be called by T, unless T is a terminated previously
163 procedure Cancel_Queued_Entry_Calls (T : Task_Id) is
164 Next_Entry_Call : Entry_Call_Link;
165 Entry_Call : Entry_Call_Link;
166 Self_Id : constant Task_Id := STPO.Self;
169 pragma Unreferenced (Caller);
170 -- Should this be removed ???
173 pragma Unreferenced (Level);
174 -- Should this be removed ???
177 pragma Assert (T = Self or else T.Common.State = Terminated);
179 for J in 1 .. T.Entry_Num loop
180 Queuing.Dequeue_Head (T.Entry_Queues (J), Entry_Call);
182 while Entry_Call /= null loop
184 -- Leave Entry_Call.Done = False, since this is cancelled
186 Caller := Entry_Call.Self;
187 Entry_Call.Exception_To_Raise := Tasking_Error'Identity;
188 Queuing.Dequeue_Head (T.Entry_Queues (J), Next_Entry_Call);
189 Level := Entry_Call.Level - 1;
191 Write_Lock (Entry_Call.Self);
192 Initialization.Wakeup_Entry_Caller
193 (Self_Id, Entry_Call, Cancelled);
194 Unlock (Entry_Call.Self);
196 Entry_Call.State := Done;
197 Entry_Call := Next_Entry_Call;
200 end Cancel_Queued_Entry_Calls;
202 ------------------------
203 -- Exit_One_ATC_Level --
204 ------------------------
206 -- Call only with abort deferred and holding lock of Self_Id.
207 -- This is a bit of common code for all entry calls.
208 -- The effect is to exit one level of ATC nesting.
210 -- If we have reached the desired ATC nesting level, reset the
211 -- requested level to effective infinity, to allow further calls.
212 -- In any case, reset Self_Id.Aborting, to allow re-raising of
215 procedure Exit_One_ATC_Level (Self_ID : Task_Id) is
217 Self_ID.ATC_Nesting_Level := Self_ID.ATC_Nesting_Level - 1;
220 (Debug.Trace (Self_ID, "EOAL: exited to ATC level: " &
221 ATC_Level'Image (Self_ID.ATC_Nesting_Level), 'A'));
223 pragma Assert (Self_ID.ATC_Nesting_Level >= 1);
225 if Self_ID.Pending_ATC_Level < ATC_Level_Infinity then
226 if Self_ID.Pending_ATC_Level = Self_ID.ATC_Nesting_Level then
227 Self_ID.Pending_ATC_Level := ATC_Level_Infinity;
228 Self_ID.Aborting := False;
230 -- Force the next Undefer_Abort to re-raise Abort_Signal
233 (Self_ID.Pending_ATC_Level < Self_ID.ATC_Nesting_Level);
235 if Self_ID.Aborting then
236 Self_ID.ATC_Hack := True;
237 Self_ID.Pending_Action := True;
241 end Exit_One_ATC_Level;
243 ----------------------
244 -- Make_Independent --
245 ----------------------
247 procedure Make_Independent is
248 Self_Id : constant Task_Id := STPO.Self;
249 Environment_Task : constant Task_Id := STPO.Environment_Task;
250 Parent : constant Task_Id := Self_Id.Common.Parent;
251 Parent_Needs_Updating : Boolean := False;
252 Master_of_Task : Integer;
255 if Self_Id.Known_Tasks_Index /= -1 then
256 Known_Tasks (Self_Id.Known_Tasks_Index) := null;
259 Initialization.Defer_Abort (Self_Id);
265 Write_Lock (Environment_Task);
266 Write_Lock (Self_Id);
268 pragma Assert (Parent = Environment_Task
269 or else Self_Id.Master_of_Task = Library_Task_Level);
271 Master_of_Task := Self_Id.Master_of_Task;
272 Self_Id.Master_of_Task := Independent_Task_Level;
274 -- The run time assumes that the parent of an independent task is the
277 if Parent /= Environment_Task then
279 -- We cannot lock three tasks at the same time, so defer the
280 -- operations on the parent.
282 Parent_Needs_Updating := True;
283 Self_Id.Common.Parent := Environment_Task;
286 -- Update Independent_Task_Count that is needed for the GLADE
287 -- termination rule. See also pending update in
288 -- System.Tasking.Stages.Check_Independent
290 Independent_Task_Count := Independent_Task_Count + 1;
294 -- Changing the parent after creation is not trivial. Do not forget
295 -- to update the old parent counts, and the new parent (i.e. the
296 -- Environment_Task) counts.
298 if Parent_Needs_Updating then
300 Parent.Awake_Count := Parent.Awake_Count - 1;
301 Parent.Alive_Count := Parent.Alive_Count - 1;
302 Environment_Task.Awake_Count := Environment_Task.Awake_Count + 1;
303 Environment_Task.Alive_Count := Environment_Task.Alive_Count + 1;
307 -- In case the environment task is already waiting for children to
309 -- ??? There may be a race condition if the environment task was not in
310 -- master completion sleep when this task was created, but now is
312 if Environment_Task.Common.State = Master_Completion_Sleep and then
313 Master_of_Task = Environment_Task.Master_Within
315 Environment_Task.Common.Wait_Count :=
316 Environment_Task.Common.Wait_Count - 1;
319 Unlock (Environment_Task);
325 Initialization.Undefer_Abort (Self_Id);
326 end Make_Independent;
332 procedure Make_Passive (Self_ID : Task_Id; Task_Completed : Boolean) is
333 C : Task_Id := Self_ID;
334 P : Task_Id := C.Common.Parent;
336 Master_Completion_Phase : Integer;
345 if Task_Completed then
346 Self_ID.Common.State := Terminated;
348 if Self_ID.Awake_Count = 0 then
350 -- We are completing via a terminate alternative.
351 -- Our parent should wait in Phase 2 of Complete_Master.
353 Master_Completion_Phase := 2;
355 pragma Assert (Task_Completed);
356 pragma Assert (Self_ID.Terminate_Alternative);
357 pragma Assert (Self_ID.Alive_Count = 1);
360 -- We are NOT on a terminate alternative.
361 -- Our parent should wait in Phase 1 of Complete_Master.
363 Master_Completion_Phase := 1;
364 pragma Assert (Self_ID.Awake_Count >= 1);
367 -- We are accepting with a terminate alternative
370 if Self_ID.Open_Accepts = null then
372 -- Somebody started a rendezvous while we had our lock open.
373 -- Skip the terminate alternative.
384 Self_ID.Terminate_Alternative := True;
385 Master_Completion_Phase := 0;
387 pragma Assert (Self_ID.Terminate_Alternative);
388 pragma Assert (Self_ID.Awake_Count >= 1);
391 if Master_Completion_Phase = 2 then
393 -- Since our Awake_Count is zero but our Alive_Count
394 -- is nonzero, we have been accepting with a terminate
395 -- alternative, and we now have been told to terminate
396 -- by a completed master (in some ancestor task) that
397 -- is waiting (with zero Awake_Count) in Phase 2 of
400 pragma Debug (Debug.Trace (Self_ID, "Make_Passive: Phase 2", 'M'));
402 pragma Assert (P /= null);
404 C.Alive_Count := C.Alive_Count - 1;
406 if C.Alive_Count > 0 then
412 -- C's count just went to zero, indicating that
413 -- all of C's dependents are terminated.
414 -- C has a parent, P.
417 -- C's count just went to zero, indicating that all of C's
418 -- dependents are terminated. C has a parent, P. Notify P that
419 -- C and its dependents have all terminated.
421 P.Alive_Count := P.Alive_Count - 1;
422 exit when P.Alive_Count > 0;
426 P := C.Common.Parent;
428 -- Environment task cannot have terminated yet
430 pragma Assert (P /= null);
436 if P.Common.State = Master_Phase_2_Sleep
437 and then C.Master_of_Task = P.Master_Within
439 pragma Assert (P.Common.Wait_Count > 0);
440 P.Common.Wait_Count := P.Common.Wait_Count - 1;
442 if P.Common.Wait_Count = 0 then
443 Wakeup (P, Master_Phase_2_Sleep);
452 -- We are terminating in Phase 1 or Complete_Master,
453 -- or are accepting on a terminate alternative.
455 C.Awake_Count := C.Awake_Count - 1;
457 if Task_Completed then
458 C.Alive_Count := C.Alive_Count - 1;
461 if C.Awake_Count > 0 or else P = null then
471 -- C's count just went to zero, indicating that all of C's
472 -- dependents are terminated or accepting with terminate alt.
473 -- C has a parent, P.
476 -- Notify P that C has gone passive
478 if P.Awake_Count > 0 then
479 P.Awake_Count := P.Awake_Count - 1;
482 if Task_Completed and then C.Alive_Count = 0 then
483 P.Alive_Count := P.Alive_Count - 1;
486 exit when P.Awake_Count > 0;
490 P := C.Common.Parent;
500 -- P has non-passive dependents
502 if P.Common.State = Master_Completion_Sleep
503 and then C.Master_of_Task = P.Master_Within
507 (Self_ID, "Make_Passive: Phase 1, parent waiting", 'M'));
509 -- If parent is in Master_Completion_Sleep, it
510 -- cannot be on a terminate alternative, hence
511 -- it cannot have Awake_Count of zero.
513 pragma Assert (P.Common.Wait_Count > 0);
514 P.Common.Wait_Count := P.Common.Wait_Count - 1;
516 if P.Common.Wait_Count = 0 then
517 Wakeup (P, Master_Completion_Sleep);
523 (Self_ID, "Make_Passive: Phase 1, parent awake", 'M'));
531 end System.Tasking.Utilities;