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) 1992-2006, 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.
35 -- These declarations are not part of the GNARLI
38 -- Turn off polling, we do not want ATC polling to take place during
39 -- tasking operations. It causes infinite loops and other problems.
41 with System
.Tasking
.Debug
;
42 -- used for Known_Tasks
44 with System
.Task_Primitives
.Operations
;
45 -- used for Write_Lock
53 with System
.Tasking
.Initialization
;
54 -- Used for Defer_Abort
56 -- Locked_Abort_To_Level
58 with System
.Tasking
.Queuing
;
59 -- used for Dequeue_Call
62 with System
.Parameters
;
63 -- used for Single_Lock
66 with System
.Traces
.Tasking
;
67 -- used for Send_Trace_Info
69 package body System
.Tasking
.Utilities
is
71 package STPO
renames System
.Task_Primitives
.Operations
;
76 use Task_Primitives
.Operations
;
79 use System
.Traces
.Tasking
;
85 -- Similar to Locked_Abort_To_Level (Self_ID, T, 0), but:
86 -- (1) caller should be holding no locks except RTS_Lock when Single_Lock
87 -- (2) may be called for tasks that have not yet been activated
88 -- (3) always aborts whole task
90 procedure Abort_One_Task
(Self_ID
: Task_Id
; T
: Task_Id
) is
92 if Parameters
.Runtime_Traces
then
93 Send_Trace_Info
(T_Abort
, Self_ID
, T
);
98 if T
.Common
.State
= Unactivated
then
99 T
.Common
.Activator
:= null;
100 T
.Common
.State
:= Terminated
;
102 Cancel_Queued_Entry_Calls
(T
);
104 elsif T
.Common
.State
/= Terminated
then
105 Initialization
.Locked_Abort_To_Level
(Self_ID
, T
, 0);
115 -- This must be called to implement the abort statement.
116 -- Much of the actual work of the abort is done by the abortee,
117 -- via the Abort_Handler signal handler, and propagation of the
118 -- Abort_Signal special exception.
120 procedure Abort_Tasks
(Tasks
: Task_List
) is
121 Self_Id
: constant Task_Id
:= STPO
.Self
;
126 -- If pragma Detect_Blocking is active then Program_Error must be
127 -- raised if this potentially blocking operation is called from a
130 if System
.Tasking
.Detect_Blocking
131 and then Self_Id
.Common
.Protected_Action_Nesting
> 0
133 Ada
.Exceptions
.Raise_Exception
134 (Program_Error
'Identity, "potentially blocking operation");
137 Initialization
.Defer_Abort_Nestable
(Self_Id
);
140 -- Really should not be nested deferral here.
141 -- Patch for code generation error that defers abort before
142 -- evaluating parameters of an entry call (at least, timed entry
143 -- calls), and so may propagate an exception that causes abort
144 -- to remain undeferred indefinitely. See C97404B. When all
145 -- such bugs are fixed, this patch can be removed.
149 for J
in Tasks
'Range loop
151 Abort_One_Task
(Self_Id
, C
);
157 if C
.Pending_ATC_Level
> 0 then
158 P
:= C
.Common
.Parent
;
161 if P
.Pending_ATC_Level
= 0 then
162 Abort_One_Task
(Self_Id
, C
);
166 P
:= P
.Common
.Parent
;
170 C
:= C
.Common
.All_Tasks_Link
;
174 Initialization
.Undefer_Abort_Nestable
(Self_Id
);
177 -------------------------------
178 -- Cancel_Queued_Entry_Calls --
179 -------------------------------
181 -- This should only be called by T, unless T is a terminated previously
184 procedure Cancel_Queued_Entry_Calls
(T
: Task_Id
) is
185 Next_Entry_Call
: Entry_Call_Link
;
186 Entry_Call
: Entry_Call_Link
;
187 Self_Id
: constant Task_Id
:= STPO
.Self
;
190 pragma Unreferenced
(Caller
);
191 -- Should this be removed ???
194 pragma Unreferenced
(Level
);
195 -- Should this be removed ???
198 pragma Assert
(T
= Self
or else T
.Common
.State
= Terminated
);
200 for J
in 1 .. T
.Entry_Num
loop
201 Queuing
.Dequeue_Head
(T
.Entry_Queues
(J
), Entry_Call
);
203 while Entry_Call
/= null loop
205 -- Leave Entry_Call.Done = False, since this is cancelled
207 Caller
:= Entry_Call
.Self
;
208 Entry_Call
.Exception_To_Raise
:= Tasking_Error
'Identity;
209 Queuing
.Dequeue_Head
(T
.Entry_Queues
(J
), Next_Entry_Call
);
210 Level
:= Entry_Call
.Level
- 1;
212 Write_Lock
(Entry_Call
.Self
);
213 Initialization
.Wakeup_Entry_Caller
214 (Self_Id
, Entry_Call
, Cancelled
);
215 Unlock
(Entry_Call
.Self
);
217 Entry_Call
.State
:= Done
;
218 Entry_Call
:= Next_Entry_Call
;
221 end Cancel_Queued_Entry_Calls
;
223 ------------------------
224 -- Exit_One_ATC_Level --
225 ------------------------
227 -- Call only with abort deferred and holding lock of Self_Id.
228 -- This is a bit of common code for all entry calls.
229 -- The effect is to exit one level of ATC nesting.
231 -- If we have reached the desired ATC nesting level, reset the
232 -- requested level to effective infinity, to allow further calls.
233 -- In any case, reset Self_Id.Aborting, to allow re-raising of
236 procedure Exit_One_ATC_Level
(Self_ID
: Task_Id
) is
238 Self_ID
.ATC_Nesting_Level
:= Self_ID
.ATC_Nesting_Level
- 1;
241 (Debug
.Trace
(Self_ID
, "EOAL: exited to ATC level: " &
242 ATC_Level
'Image (Self_ID
.ATC_Nesting_Level
), 'A'));
244 pragma Assert
(Self_ID
.ATC_Nesting_Level
>= 1);
246 if Self_ID
.Pending_ATC_Level
< ATC_Level_Infinity
then
247 if Self_ID
.Pending_ATC_Level
= Self_ID
.ATC_Nesting_Level
then
248 Self_ID
.Pending_ATC_Level
:= ATC_Level_Infinity
;
249 Self_ID
.Aborting
:= False;
251 -- Force the next Undefer_Abort to re-raise Abort_Signal
254 (Self_ID
.Pending_ATC_Level
< Self_ID
.ATC_Nesting_Level
);
256 if Self_ID
.Aborting
then
257 Self_ID
.ATC_Hack
:= True;
258 Self_ID
.Pending_Action
:= True;
262 end Exit_One_ATC_Level
;
264 ----------------------
265 -- Make_Independent --
266 ----------------------
268 procedure Make_Independent
is
269 Self_Id
: constant Task_Id
:= STPO
.Self
;
270 Environment_Task
: constant Task_Id
:= STPO
.Environment_Task
;
271 Parent
: constant Task_Id
:= Self_Id
.Common
.Parent
;
272 Parent_Needs_Updating
: Boolean := False;
273 Master_of_Task
: Integer;
276 if Self_Id
.Known_Tasks_Index
/= -1 then
277 Known_Tasks
(Self_Id
.Known_Tasks_Index
) := null;
280 Initialization
.Defer_Abort
(Self_Id
);
286 Write_Lock
(Environment_Task
);
287 Write_Lock
(Self_Id
);
289 pragma Assert
(Parent
= Environment_Task
290 or else Self_Id
.Master_of_Task
= Library_Task_Level
);
292 Master_of_Task
:= Self_Id
.Master_of_Task
;
293 Self_Id
.Master_of_Task
:= Independent_Task_Level
;
295 -- The run time assumes that the parent of an independent task is the
298 if Parent
/= Environment_Task
then
300 -- We cannot lock three tasks at the same time, so defer the
301 -- operations on the parent.
303 Parent_Needs_Updating
:= True;
304 Self_Id
.Common
.Parent
:= Environment_Task
;
307 -- Update Independent_Task_Count that is needed for the GLADE
308 -- termination rule. See also pending update in
309 -- System.Tasking.Stages.Check_Independent
311 Independent_Task_Count
:= Independent_Task_Count
+ 1;
315 -- Changing the parent after creation is not trivial. Do not forget
316 -- to update the old parent counts, and the new parent (i.e. the
317 -- Environment_Task) counts.
319 if Parent_Needs_Updating
then
321 Parent
.Awake_Count
:= Parent
.Awake_Count
- 1;
322 Parent
.Alive_Count
:= Parent
.Alive_Count
- 1;
323 Environment_Task
.Awake_Count
:= Environment_Task
.Awake_Count
+ 1;
324 Environment_Task
.Alive_Count
:= Environment_Task
.Alive_Count
+ 1;
328 -- In case the environment task is already waiting for children to
330 -- ??? There may be a race condition if the environment task was not in
331 -- master completion sleep when this task was created, but now is
333 if Environment_Task
.Common
.State
= Master_Completion_Sleep
and then
334 Master_of_Task
= Environment_Task
.Master_Within
336 Environment_Task
.Common
.Wait_Count
:=
337 Environment_Task
.Common
.Wait_Count
- 1;
340 Unlock
(Environment_Task
);
346 Initialization
.Undefer_Abort
(Self_Id
);
347 end Make_Independent
;
353 procedure Make_Passive
(Self_ID
: Task_Id
; Task_Completed
: Boolean) is
354 C
: Task_Id
:= Self_ID
;
355 P
: Task_Id
:= C
.Common
.Parent
;
357 Master_Completion_Phase
: Integer;
366 if Task_Completed
then
367 Self_ID
.Common
.State
:= Terminated
;
369 if Self_ID
.Awake_Count
= 0 then
371 -- We are completing via a terminate alternative.
372 -- Our parent should wait in Phase 2 of Complete_Master.
374 Master_Completion_Phase
:= 2;
376 pragma Assert
(Task_Completed
);
377 pragma Assert
(Self_ID
.Terminate_Alternative
);
378 pragma Assert
(Self_ID
.Alive_Count
= 1);
381 -- We are NOT on a terminate alternative.
382 -- Our parent should wait in Phase 1 of Complete_Master.
384 Master_Completion_Phase
:= 1;
385 pragma Assert
(Self_ID
.Awake_Count
= 1);
388 -- We are accepting with a terminate alternative
391 if Self_ID
.Open_Accepts
= null then
393 -- Somebody started a rendezvous while we had our lock open.
394 -- Skip the terminate alternative.
405 Self_ID
.Terminate_Alternative
:= True;
406 Master_Completion_Phase
:= 0;
408 pragma Assert
(Self_ID
.Terminate_Alternative
);
409 pragma Assert
(Self_ID
.Awake_Count
>= 1);
412 if Master_Completion_Phase
= 2 then
414 -- Since our Awake_Count is zero but our Alive_Count
415 -- is nonzero, we have been accepting with a terminate
416 -- alternative, and we now have been told to terminate
417 -- by a completed master (in some ancestor task) that
418 -- is waiting (with zero Awake_Count) in Phase 2 of
421 pragma Debug
(Debug
.Trace
(Self_ID
, "Make_Passive: Phase 2", 'M'));
423 pragma Assert
(P
/= null);
425 C
.Alive_Count
:= C
.Alive_Count
- 1;
427 if C
.Alive_Count
> 0 then
433 -- C's count just went to zero, indicating that
434 -- all of C's dependents are terminated.
435 -- C has a parent, P.
438 -- C's count just went to zero, indicating that all of C's
439 -- dependents are terminated. C has a parent, P. Notify P that
440 -- C and its dependents have all terminated.
442 P
.Alive_Count
:= P
.Alive_Count
- 1;
443 exit when P
.Alive_Count
> 0;
447 P
:= C
.Common
.Parent
;
449 -- Environment task cannot have terminated yet
451 pragma Assert
(P
/= null);
457 pragma Assert
(P
.Awake_Count
/= 0);
459 if P
.Common
.State
= Master_Phase_2_Sleep
460 and then C
.Master_of_Task
= P
.Master_Within
462 pragma Assert
(P
.Common
.Wait_Count
> 0);
463 P
.Common
.Wait_Count
:= P
.Common
.Wait_Count
- 1;
465 if P
.Common
.Wait_Count
= 0 then
466 Wakeup
(P
, Master_Phase_2_Sleep
);
475 -- We are terminating in Phase 1 or Complete_Master,
476 -- or are accepting on a terminate alternative.
478 C
.Awake_Count
:= C
.Awake_Count
- 1;
480 if Task_Completed
then
481 pragma Assert
(Self_ID
.Awake_Count
= 0);
482 C
.Alive_Count
:= C
.Alive_Count
- 1;
485 if C
.Awake_Count
> 0 or else P
= null then
495 -- C's count just went to zero, indicating that all of C's
496 -- dependents are terminated or accepting with terminate alt.
497 -- C has a parent, P.
500 -- Notify P that C has gone passive
502 P
.Awake_Count
:= P
.Awake_Count
- 1;
504 if Task_Completed
and then C
.Alive_Count
= 0 then
505 P
.Alive_Count
:= P
.Alive_Count
- 1;
508 exit when P
.Awake_Count
> 0;
512 P
:= C
.Common
.Parent
;
522 -- P has non-passive dependents
524 if P
.Common
.State
= Master_Completion_Sleep
525 and then C
.Master_of_Task
= P
.Master_Within
529 (Self_ID
, "Make_Passive: Phase 1, parent waiting", 'M'));
531 -- If parent is in Master_Completion_Sleep, it
532 -- cannot be on a terminate alternative, hence
533 -- it cannot have Awake_Count of zero.
535 pragma Assert
(P
.Common
.Wait_Count
> 0);
536 P
.Common
.Wait_Count
:= P
.Common
.Wait_Count
- 1;
538 if P
.Common
.Wait_Count
= 0 then
539 Wakeup
(P
, Master_Completion_Sleep
);
545 (Self_ID
, "Make_Passive: Phase 1, parent awake", 'M'));
553 end System
.Tasking
.Utilities
;