1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
5 -- S Y S T E M . T A S K I N G . S T A G E S --
9 -- Copyright (C) 1992-2023, 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 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. --
18 -- As a special exception under Section 7 of GPL version 3, you are granted --
19 -- additional permissions described in the GCC Runtime Library Exception, --
20 -- version 3.1, as published by the Free Software Foundation. --
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/>. --
27 -- GNARL was developed by the GNARL team at Florida State University. --
28 -- Extensive contributions were provided by Ada Core Technologies, Inc. --
30 ------------------------------------------------------------------------------
32 pragma Partition_Elaboration_Policy
(Concurrent
);
33 -- This package only implements the concurrent elaboration policy. This pragma
34 -- will enforce it (and detect conflicts with user specified policy).
37 with Ada
.Unchecked_Deallocation
;
38 with Ada
.Task_Initialization
;
40 with System
.Interrupt_Management
;
41 with System
.Tasking
.Debug
;
42 with System
.Address_Image
;
43 with System
.Task_Primitives
;
44 with System
.Task_Primitives
.Operations
;
45 with System
.Tasking
.Utilities
;
46 with System
.Tasking
.Queuing
;
47 with System
.Tasking
.Rendezvous
;
48 with System
.OS_Primitives
;
49 with System
.Secondary_Stack
;
50 with System
.Restrictions
;
51 with System
.Standard_Library
;
52 with System
.Stack_Usage
;
53 with System
.Storage_Elements
;
55 with System
.Soft_Links
;
56 -- These are procedure pointers to non-tasking routines that use task
57 -- specific data. In the absence of tasking, these routines refer to global
58 -- data. In the presence of tasking, they must be replaced with pointers to
59 -- task-specific versions. Also used for Create_TSD, Destroy_TSD, Get_Current
60 -- _Excep, Finalize_Library_Objects, Task_Termination, Handler.
62 with System
.Tasking
.Initialization
;
63 pragma Elaborate_All
(System
.Tasking
.Initialization
);
64 -- This insures that tasking is initialized if any tasks are created
66 package body System
.Tasking
.Stages
is
68 package STPO
renames System
.Task_Primitives
.Operations
;
69 package SSL
renames System
.Soft_Links
;
70 package SSE
renames System
.Storage_Elements
;
76 use Task_Primitives
.Operations
;
78 -----------------------
79 -- Local Subprograms --
80 -----------------------
83 Ada
.Unchecked_Deallocation
(Ada_Task_Control_Block
, Task_Id
);
85 procedure Trace_Unhandled_Exception_In_Task
(Self_Id
: Task_Id
);
86 -- This procedure outputs the task specific message for exception
89 procedure Task_Wrapper
(Self_ID
: Task_Id
);
90 pragma Convention
(C
, Task_Wrapper
);
91 -- This is the procedure that is called by the GNULL from the new context
92 -- when a task is created. It waits for activation and then calls the task
93 -- body procedure. When the task body procedure completes, it terminates
96 -- The Task_Wrapper's address will be provided to the underlying threads
97 -- library as the task entry point. Convention C is what makes most sense
98 -- for that purpose (Export C would make the function globally visible,
99 -- and affect the link name on which GDB depends). This will in addition
100 -- trigger an automatic stack alignment suitable for GCC's assumptions if
103 -- "Vulnerable_..." in the procedure names below means they must be called
104 -- with abort deferred.
106 procedure Vulnerable_Complete_Task
(Self_ID
: Task_Id
);
107 -- Complete the calling task. This procedure must be called with
108 -- abort deferred. It should only be called by Complete_Task and
109 -- Finalize_Global_Tasks (for the environment task).
111 procedure Vulnerable_Complete_Master
(Self_ID
: Task_Id
);
112 -- Complete the current master of the calling task. This procedure
113 -- must be called with abort deferred. It should only be called by
114 -- Vulnerable_Complete_Task and Complete_Master.
116 procedure Vulnerable_Complete_Activation
(Self_ID
: Task_Id
);
117 -- Signal to Self_ID's activator that Self_ID has completed activation.
118 -- This procedure must be called with abort deferred.
120 procedure Abort_Dependents
(Self_ID
: Task_Id
);
121 -- Abort all the direct dependents of Self at its current master nesting
122 -- level, plus all of their dependents, transitively. RTS_Lock should be
123 -- locked by the caller.
125 procedure Vulnerable_Free_Task
(T
: Task_Id
);
126 -- Recover all runtime system storage associated with the task T. This
127 -- should only be called after T has terminated and will no longer be
130 -- For tasks created by an allocator that fails, due to an exception, it is
131 -- called from Expunge_Unactivated_Tasks.
133 -- Different code is used at master completion, in Terminate_Dependents,
134 -- due to a need for tighter synchronization with the master.
136 ----------------------
137 -- Abort_Dependents --
138 ----------------------
140 procedure Abort_Dependents
(Self_ID
: Task_Id
) is
144 -- Each task C will take care of its own dependents, so there is no
145 -- need to worry about them here. In fact, it would be wrong to abort
146 -- indirect dependents here, because we can't distinguish between
147 -- duplicate master ids. For example, suppose we have three nested
148 -- task bodies T1,T2,T3. And suppose T1 also calls P which calls Q (and
149 -- both P and Q are task masters). Q will have the same master id as
150 -- Master_Of_Task of T3. Previous versions of this would abort T3 when
151 -- Q calls Complete_Master, which was completely wrong.
156 P
:= C
.Common
.Parent
;
159 if C
.Master_Of_Task
= Self_ID
.Master_Within
then
161 (Debug
.Trace
(Self_ID
, "Aborting", 'X', C
));
162 Utilities
.Abort_One_Task
(Self_ID
, C
);
163 C
.Dependents_Aborted
:= True;
167 C
:= C
.Common
.All_Tasks_Link
;
170 Self_ID
.Dependents_Aborted
:= True;
171 end Abort_Dependents
;
177 procedure Abort_Tasks
(Tasks
: Task_List
) is
179 Utilities
.Abort_Tasks
(Tasks
);
186 -- Note that locks of activator and activated task are both locked here.
187 -- This is necessary because C.Common.State and Self.Common.Wait_Count have
188 -- to be synchronized. This is safe from deadlock because the activator is
189 -- always created before the activated task. That satisfies our
190 -- in-order-of-creation ATCB locking policy.
192 -- At one point, we may also lock the parent, if the parent is different
193 -- from the activator. That is also consistent with the lock ordering
194 -- policy, since the activator cannot be created before the parent.
196 -- Since we are holding both the activator's lock, and Task_Wrapper locks
197 -- that before it does anything more than initialize the low-level ATCB
198 -- components, it should be safe to wait to update the counts until we see
199 -- that the thread creation is successful.
201 -- If the thread creation fails, we do need to close the entries of the
202 -- task. The first phase, of dequeuing calls, only requires locking the
203 -- acceptor's ATCB, but the waking up of the callers requires locking the
204 -- caller's ATCB. We cannot safely do this while we are holding other
205 -- locks. Therefore, the queue-clearing operation is done in a separate
206 -- pass over the activation chain.
208 procedure Activate_Tasks
(Chain_Access
: Activation_Chain_Access
) is
209 Self_ID
: constant Task_Id
:= STPO
.Self
;
212 Next_C
, Last_C
: Task_Id
;
213 Activate_Prio
: System
.Any_Priority
;
215 All_Elaborated
: Boolean := True;
218 -- If pragma Detect_Blocking is active, then we must check whether this
219 -- potentially blocking operation is called from a protected action.
221 if System
.Tasking
.Detect_Blocking
222 and then Self_ID
.Common
.Protected_Action_Nesting
> 0
224 raise Program_Error
with "potentially blocking operation";
228 (Debug
.Trace
(Self_ID
, "Activate_Tasks", 'C'));
230 Initialization
.Defer_Abort_Nestable
(Self_ID
);
232 pragma Assert
(Self_ID
.Common
.Wait_Count
= 0);
234 -- Lock RTS_Lock, to prevent activated tasks from racing ahead before
235 -- we finish activating the chain.
239 -- Check that all task bodies have been elaborated
241 C
:= Chain_Access
.T_ID
;
244 if C
.Common
.Elaborated
/= null
245 and then not C
.Common
.Elaborated
.all
247 All_Elaborated
:= False;
250 -- Reverse the activation chain so that tasks are activated in the
251 -- same order they're declared.
253 Next_C
:= C
.Common
.Activation_Link
;
254 C
.Common
.Activation_Link
:= Last_C
;
259 Chain_Access
.T_ID
:= Last_C
;
261 if not All_Elaborated
then
263 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
264 raise Program_Error
with "Some tasks have not been elaborated";
267 -- Activate all the tasks in the chain. Creation of the thread of
268 -- control was deferred until activation. So create it now.
270 C
:= Chain_Access
.T_ID
;
272 if C
.Common
.State
/= Terminated
then
273 pragma Assert
(C
.Common
.State
= Unactivated
);
275 P
:= C
.Common
.Parent
;
280 (if C
.Common
.Base_Priority
< Get_Priority
(Self_ID
)
281 then Get_Priority
(Self_ID
)
282 else C
.Common
.Base_Priority
);
284 System
.Task_Primitives
.Operations
.Create_Task
285 (C
, Task_Wrapper
'Address,
287 (C
.Common
.Compiler_Data
.Pri_Stack_Info
.Size
),
288 Activate_Prio
, Success
);
290 -- There would be a race between the created task and the creator
291 -- to do the following initialization, if we did not have a
292 -- Lock/Unlock_RTS pair in the task wrapper to prevent it from
296 C
.Common
.State
:= Activating
;
299 P
.Awake_Count
:= P
.Awake_Count
+ 1;
300 P
.Alive_Count
:= P
.Alive_Count
+ 1;
302 if P
.Common
.State
= Master_Completion_Sleep
and then
303 C
.Master_Of_Task
= P
.Master_Within
305 pragma Assert
(Self_ID
/= P
);
306 P
.Common
.Wait_Count
:= P
.Common
.Wait_Count
+ 1;
309 for J
in System
.Tasking
.Debug
.Known_Tasks
'Range loop
310 if System
.Tasking
.Debug
.Known_Tasks
(J
) = null then
311 System
.Tasking
.Debug
.Known_Tasks
(J
) := C
;
312 C
.Known_Tasks_Index
:= J
;
317 if Global_Task_Debug_Event_Set
then
318 Debug
.Signal_Debug_Event
319 (Debug
.Debug_Event_Activating
, C
);
322 C
.Common
.State
:= Runnable
;
328 -- No need to set Awake_Count, State, etc. here since the loop
329 -- below will do that for any Unactivated tasks.
333 Self_ID
.Common
.Activation_Failed
:= True;
337 C
:= C
.Common
.Activation_Link
;
342 -- Close the entries of any tasks that failed thread creation, and count
343 -- those that have not finished activation.
345 Write_Lock
(Self_ID
);
346 Self_ID
.Common
.State
:= Activator_Sleep
;
348 C
:= Chain_Access
.T_ID
;
352 if C
.Common
.State
= Unactivated
then
353 C
.Common
.Activator
:= null;
354 C
.Common
.State
:= Terminated
;
356 Utilities
.Cancel_Queued_Entry_Calls
(C
);
358 elsif C
.Common
.Activator
/= null then
359 Self_ID
.Common
.Wait_Count
:= Self_ID
.Common
.Wait_Count
+ 1;
363 P
:= C
.Common
.Activation_Link
;
364 C
.Common
.Activation_Link
:= null;
368 -- Wait for the activated tasks to complete activation. It is
369 -- unsafe to abort any of these tasks until the count goes to zero.
372 exit when Self_ID
.Common
.Wait_Count
= 0;
373 Sleep
(Self_ID
, Activator_Sleep
);
376 Self_ID
.Common
.State
:= Runnable
;
379 -- Remove the tasks from the chain
381 Chain_Access
.T_ID
:= null;
382 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
384 if Self_ID
.Common
.Activation_Failed
then
385 Self_ID
.Common
.Activation_Failed
:= False;
386 raise Tasking_Error
with "Failure during activation";
390 -------------------------
391 -- Complete_Activation --
392 -------------------------
394 procedure Complete_Activation
is
395 Self_ID
: constant Task_Id
:= STPO
.Self
;
398 Initialization
.Defer_Abort_Nestable
(Self_ID
);
399 Vulnerable_Complete_Activation
(Self_ID
);
400 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
402 -- ??? Why do we need to allow for nested deferral here?
404 end Complete_Activation
;
406 ---------------------
407 -- Complete_Master --
408 ---------------------
410 procedure Complete_Master
is
411 Self_ID
: constant Task_Id
:= STPO
.Self
;
414 (Self_ID
.Deferral_Level
> 0
415 or else not System
.Restrictions
.Abort_Allowed
);
416 Vulnerable_Complete_Master
(Self_ID
);
423 -- See comments on Vulnerable_Complete_Task for details
425 procedure Complete_Task
is
426 Self_ID
: constant Task_Id
:= STPO
.Self
;
430 (Self_ID
.Deferral_Level
> 0
431 or else not System
.Restrictions
.Abort_Allowed
);
433 Vulnerable_Complete_Task
(Self_ID
);
435 -- All of our dependents have terminated, never undefer abort again
443 -- Compiler interface only. Do not call from within the RTS. This must be
444 -- called to create a new task.
446 procedure Create_Task
448 Stack_Size
: System
.Parameters
.Size_Type
;
449 Secondary_Stack_Size
: System
.Parameters
.Size_Type
;
450 Task_Info
: System
.Task_Info
.Task_Info_Type
;
452 Relative_Deadline
: Ada
.Real_Time
.Time_Span
;
453 Domain
: Dispatching_Domain_Access
;
454 Num_Entries
: Task_Entry_Index
;
455 Master
: Master_Level
;
456 State
: Task_Procedure_Access
;
457 Discriminants
: System
.Address
;
458 Elaborated
: Access_Boolean
;
459 Chain
: in out Activation_Chain
;
461 Created_Task
: out Task_Id
)
464 Self_ID
: constant Task_Id
:= STPO
.Self
;
466 Base_Priority
: System
.Any_Priority
;
468 Base_CPU
: System
.Multiprocessors
.CPU_Range
;
470 use type System
.Multiprocessors
.CPU_Range
;
472 pragma Unreferenced
(Relative_Deadline
);
473 -- EDF scheduling is not supported by any of the target platforms so
474 -- this parameter is not passed any further.
477 -- If Master is greater than the current master, it means that Master
478 -- has already awaited its dependent tasks. This raises Program_Error,
479 -- by 4.8(10.3/2). See AI-280. Ignore this check for foreign threads.
481 if Self_ID
.Master_Of_Task
/= Foreign_Task_Level
482 and then Master
> Self_ID
.Master_Within
484 raise Program_Error
with
485 "create task after awaiting termination";
488 -- If pragma Detect_Blocking is active must be checked whether this
489 -- potentially blocking operation is called from a protected action.
491 if System
.Tasking
.Detect_Blocking
492 and then Self_ID
.Common
.Protected_Action_Nesting
> 0
494 raise Program_Error
with "potentially blocking operation";
497 pragma Debug
(Debug
.Trace
(Self_ID
, "Create_Task", 'C'));
500 (if Priority
= Unspecified_Priority
501 then Self_ID
.Common
.Base_Priority
502 else System
.Any_Priority
(Priority
));
504 -- Legal values of CPU are the special Unspecified_CPU value which is
505 -- inserted by the compiler for tasks without CPU aspect, and those in
506 -- the range of CPU_Range but no greater than Number_Of_CPUs. Otherwise
507 -- the task is defined to have failed, and it becomes a completed task
510 if CPU
/= Unspecified_CPU
511 and then (CPU
< Integer (System
.Multiprocessors
.CPU_Range
'First)
513 CPU
> Integer (System
.Multiprocessors
.Number_Of_CPUs
))
515 raise Tasking_Error
with "CPU not in range";
517 -- Normal CPU affinity
520 -- When the application code says nothing about the task affinity
521 -- (task without CPU aspect) then the compiler inserts the value
522 -- Unspecified_CPU which indicates to the run-time library that
523 -- the task will activate and execute on the same processor as its
524 -- activating task if the activating task is assigned a processor
528 (if CPU
= Unspecified_CPU
529 then Self_ID
.Common
.Base_CPU
530 else System
.Multiprocessors
.CPU_Range
(CPU
));
533 -- Find parent P of new Task, via master level number. Independent
534 -- tasks should have Parent = Environment_Task, and all tasks created
535 -- by independent tasks are also independent. See, for example,
536 -- s-interr.adb, where Interrupt_Manager does "new Server_Task". The
537 -- access type is at library level, so the parent of the Server_Task
538 -- is Environment_Task.
542 if P
.Master_Of_Task
<= Independent_Task_Level
then
543 P
:= Environment_Task
;
545 while P
/= null and then P
.Master_Of_Task
>= Master
loop
546 P
:= P
.Common
.Parent
;
550 Initialization
.Defer_Abort_Nestable
(Self_ID
);
553 T
:= New_ATCB
(Num_Entries
);
556 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
557 raise Storage_Error
with "Cannot allocate task";
560 -- RTS_Lock is used by Abort_Dependents and Abort_Tasks. Up to this
561 -- point, it is possible that we may be part of a family of tasks that
565 Write_Lock
(Self_ID
);
567 -- Now, we must check that we have not been aborted. If so, we should
568 -- give up on creating this task, and simply return.
570 if not Self_ID
.Callable
then
571 pragma Assert
(Self_ID
.Pending_ATC_Level
= Level_Completed_Task
);
572 pragma Assert
(Self_ID
.Pending_Action
);
574 (Chain
.T_ID
= null or else Chain
.T_ID
.Common
.State
= Unactivated
);
578 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
580 -- ??? Should never get here
582 pragma Assert
(Standard
.False);
583 raise Standard
'Abort_Signal;
586 Initialize_ATCB
(Self_ID
, State
, Discriminants
, P
, Elaborated
,
587 Base_Priority
, Base_CPU
, Domain
, Task_Info
, Stack_Size
, T
, Success
);
593 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
594 raise Storage_Error
with "Failed to initialize task";
597 if Master
= Foreign_Task_Level
+ 2 then
599 -- This should not happen, except when a foreign task creates non
600 -- library-level Ada tasks. In this case, we pretend the master is
601 -- a regular library level task, otherwise the run-time will get
602 -- confused when waiting for these tasks to terminate.
604 T
.Master_Of_Task
:= Library_Task_Level
;
607 T
.Master_Of_Task
:= Master
;
610 T
.Master_Within
:= T
.Master_Of_Task
+ 1;
612 for L
in T
.Entry_Calls
'Range loop
613 T
.Entry_Calls
(L
).Self
:= T
;
614 T
.Entry_Calls
(L
).Level
:= L
;
617 if Task_Image
'Length = 0 then
618 T
.Common
.Task_Image_Len
:= 0;
621 T
.Common
.Task_Image
(1) := Task_Image
(Task_Image
'First);
623 -- Remove unwanted blank space generated by 'Image
625 for J
in Task_Image
'First + 1 .. Task_Image
'Last loop
626 if Task_Image
(J
) /= ' '
627 or else Task_Image
(J
- 1) /= '('
630 T
.Common
.Task_Image
(Len
) := Task_Image
(J
);
631 exit when Len
= T
.Common
.Task_Image
'Last;
635 T
.Common
.Task_Image_Len
:= Len
;
638 -- Note: we used to have code here to initialize T.Common.Domain, but
639 -- that is not needed, since this is initialized in System.Tasking.
644 -- The CPU associated to the task (if any) must belong to the
645 -- dispatching domain.
647 if Base_CPU
/= System
.Multiprocessors
.Not_A_Specific_CPU
649 (Base_CPU
not in T
.Common
.Domain
'Range
650 or else not T
.Common
.Domain
(Base_CPU
))
652 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
653 raise Tasking_Error
with "CPU not in dispatching domain";
656 -- To handle the interaction between pragma CPU and dispatching domains
657 -- we need to signal that this task is being allocated to a processor.
658 -- This is needed only for tasks belonging to the system domain (the
659 -- creation of new dispatching domains can only take processors from the
660 -- system domain) and only before the environment task calls the main
661 -- procedure (dispatching domains cannot be created after this).
663 if Base_CPU
/= System
.Multiprocessors
.Not_A_Specific_CPU
664 and then T
.Common
.Domain
= System
.Tasking
.System_Domain
665 and then not System
.Tasking
.Dispatching_Domains_Frozen
667 -- Increase the number of tasks attached to the CPU to which this
668 -- task is being moved.
670 Dispatching_Domain_Tasks
(Base_CPU
) :=
671 Dispatching_Domain_Tasks
(Base_CPU
) + 1;
674 -- Create the secondary stack for the task as early as possible during
675 -- in the creation of a task, since it may be used by the operation of
676 -- Ada code within the task.
679 SSL
.Create_TSD
(T
.Common
.Compiler_Data
, null, Secondary_Stack_Size
);
682 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
683 raise Storage_Error
with "Secondary stack could not be allocated";
686 T
.Common
.Activation_Link
:= Chain
.T_ID
;
689 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
693 (Self_ID
, "Created task in " & T
.Master_Of_Task
'Img, 'C', T
));
700 function Current_Master
return Master_Level
is
702 return STPO
.Self
.Master_Within
;
709 procedure Enter_Master
is
710 Self_ID
: constant Task_Id
:= STPO
.Self
;
712 Self_ID
.Master_Within
:= Self_ID
.Master_Within
+ 1;
715 (Self_ID
, "Enter_Master ->" & Self_ID
.Master_Within
'Img, 'M'));
718 -------------------------------
719 -- Expunge_Unactivated_Tasks --
720 -------------------------------
722 -- See procedure Close_Entries for the general case
724 procedure Expunge_Unactivated_Tasks
(Chain
: in out Activation_Chain
) is
725 Self_ID
: constant Task_Id
:= STPO
.Self
;
727 Call
: Entry_Call_Link
;
732 (Debug
.Trace
(Self_ID
, "Expunge_Unactivated_Tasks", 'C'));
734 Initialization
.Defer_Abort_Nestable
(Self_ID
);
737 -- Experimentation has shown that abort is sometimes (but not always)
738 -- already deferred when this is called.
740 -- That may indicate an error. Find out what is going on
744 pragma Assert
(C
.Common
.State
= Unactivated
);
746 Temp
:= C
.Common
.Activation_Link
;
748 if C
.Common
.State
= Unactivated
then
752 for J
in 1 .. C
.Entry_Num
loop
753 Queuing
.Dequeue_Head
(C
.Entry_Queues
(J
), Call
);
754 pragma Assert
(Call
= null);
759 Initialization
.Remove_From_All_Tasks_List
(C
);
762 Vulnerable_Free_Task
(C
);
768 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
769 end Expunge_Unactivated_Tasks
;
771 ---------------------------
772 -- Finalize_Global_Tasks --
773 ---------------------------
776 -- We have a potential problem here if finalization of global objects does
777 -- anything with signals or the timer server, since by that time those
778 -- servers have terminated.
780 -- It is hard to see how that would occur
782 -- However, a better solution might be to do all this finalization
783 -- using the global finalization chain.
785 procedure Finalize_Global_Tasks
is
786 Self_ID
: constant Task_Id
:= STPO
.Self
;
792 (Int
: System
.Interrupt_Management
.Interrupt_ID
) return Character;
793 pragma Import
(C
, State
, "__gnat_get_interrupt_state");
794 -- Get interrupt state for interrupt number Int. Defined in init.c
796 Default
: constant Character := 's';
797 -- 's' Interrupt_State pragma set state to System (use "default"
801 if Self_ID
.Deferral_Level
= 0 then
803 -- In principle, we should be able to predict whether abort is
804 -- already deferred here (and it should not be deferred yet but in
805 -- practice it seems Finalize_Global_Tasks is being called sometimes,
806 -- from RTS code for exceptions, with abort already deferred.
808 Initialization
.Defer_Abort_Nestable
(Self_ID
);
810 -- Never undefer again
813 -- This code is only executed by the environment task
815 pragma Assert
(Self_ID
= Environment_Task
);
817 -- Set Environment_Task'Callable to false to notify library-level tasks
818 -- that it is waiting for them.
820 Self_ID
.Callable
:= False;
822 -- Exit level 2 master, for normal tasks in library-level packages
826 -- Force termination of "independent" library-level server tasks
829 Abort_Dependents
(Self_ID
);
832 -- We need to explicitly wait for the task to be terminated here
833 -- because on true concurrent system, we may end this procedure before
834 -- the tasks are really terminated.
836 Write_Lock
(Self_ID
);
838 -- If the Abort_Task signal is set to system, it means that we may
839 -- not have been able to abort all independent tasks (in particular,
840 -- Server_Task may be blocked, waiting for a signal), in which case, do
841 -- not wait for Independent_Task_Count to go down to 0. We arbitrarily
842 -- limit the number of loop iterations; if an independent task does not
843 -- terminate, we do not want to hang here. In that case, the thread will
844 -- be terminated when the process exits.
846 if State
(System
.Interrupt_Management
.Abort_Task_Interrupt
) /= Default
848 for J
in 1 .. 10 loop
849 exit when Utilities
.Independent_Task_Count
= 0;
851 -- We used to yield here, but this did not take into account low
852 -- priority tasks that would cause dead lock in some cases (true
856 (Self_ID
, 0.01, System
.OS_Primitives
.Relative
,
857 Self_ID
.Common
.State
, Ignore_1
, Ignore_2
);
861 -- ??? On multi-processor environments, it seems that the above loop
862 -- isn't sufficient, so we need to add an additional delay.
865 (Self_ID
, 0.01, System
.OS_Primitives
.Relative
,
866 Self_ID
.Common
.State
, Ignore_1
, Ignore_2
);
870 -- Complete the environment task
872 Vulnerable_Complete_Task
(Self_ID
);
874 -- Handle normal task termination by the environment task, but only
875 -- for the normal task termination. In the case of Abnormal and
876 -- Unhandled_Exception they must have been handled before, and the
877 -- task termination soft link must have been changed so the task
878 -- termination routine is not executed twice.
880 SSL
.Task_Termination_Handler
.all (Ada
.Exceptions
.Null_Occurrence
);
882 -- Finalize all library-level controlled objects
884 if not SSL
."=" (SSL
.Finalize_Library_Objects
, null) then
885 SSL
.Finalize_Library_Objects
.all;
888 -- Reset the soft links to non-tasking
890 SSL
.Abort_Defer
:= SSL
.Abort_Defer_NT
'Access;
891 SSL
.Abort_Undefer
:= SSL
.Abort_Undefer_NT
'Access;
892 SSL
.Lock_Task
:= SSL
.Task_Lock_NT
'Access;
893 SSL
.Unlock_Task
:= SSL
.Task_Unlock_NT
'Access;
894 SSL
.Get_Jmpbuf_Address
:= SSL
.Get_Jmpbuf_Address_NT
'Access;
895 SSL
.Set_Jmpbuf_Address
:= SSL
.Set_Jmpbuf_Address_NT
'Access;
896 SSL
.Get_Sec_Stack
:= SSL
.Get_Sec_Stack_NT
'Access;
897 SSL
.Set_Sec_Stack
:= SSL
.Set_Sec_Stack_NT
'Access;
898 SSL
.Check_Abort_Status
:= SSL
.Check_Abort_Status_NT
'Access;
899 SSL
.Get_Stack_Info
:= SSL
.Get_Stack_Info_NT
'Access;
901 -- Don't bother trying to finalize Initialization.Global_Task_Lock
902 -- and System.Task_Primitives.RTS_Lock.
904 end Finalize_Global_Tasks
;
910 procedure Free_Task
(T
: Task_Id
) is
911 Self_Id
: constant Task_Id
:= Self
;
914 Initialization
.Task_Lock
(Self_Id
);
916 if T
.Common
.State
= Terminated
then
918 -- It is not safe to call Abort_Defer or Write_Lock at this stage
921 Initialization
.Finalize_Attributes
(T
);
922 Initialization
.Remove_From_All_Tasks_List
(T
);
925 Initialization
.Task_Unlock
(Self_Id
);
927 System
.Task_Primitives
.Operations
.Finalize_TCB
(T
);
930 -- If the task is not terminated, then mark the task as to be freed
933 T
.Free_On_Termination
:= True;
934 Initialization
.Task_Unlock
(Self_Id
);
938 ---------------------------
939 -- Move_Activation_Chain --
940 ---------------------------
942 procedure Move_Activation_Chain
943 (From
, To
: Activation_Chain_Access
;
944 New_Master
: Master_ID
)
946 Self_ID
: constant Task_Id
:= STPO
.Self
;
951 (Debug
.Trace
(Self_ID
, "Move_Activation_Chain", 'C'));
953 -- Nothing to do if From is empty, and we can check that without
962 Initialization
.Defer_Abort_Nestable
(Self_ID
);
964 -- Loop through the From chain, changing their Master_Of_Task fields,
965 -- and to find the end of the chain.
968 C
.Master_Of_Task
:= New_Master
;
969 exit when C
.Common
.Activation_Link
= null;
970 C
:= C
.Common
.Activation_Link
;
973 -- Hook From in at the start of To
975 C
.Common
.Activation_Link
:= To
.all.T_ID
;
976 To
.all.T_ID
:= From
.all.T_ID
;
980 From
.all.T_ID
:= null;
982 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
983 end Move_Activation_Chain
;
989 -- The task wrapper is a procedure that is called first for each task body
990 -- and which in turn calls the compiler-generated task body procedure.
991 -- The wrapper's main job is to do initialization for the task. It also
992 -- has some locally declared objects that serve as per-task local data.
993 -- Task finalization is done by Complete_Task, which is called from an
994 -- at-end handler that the compiler generates.
996 procedure Task_Wrapper
(Self_ID
: Task_Id
) is
997 use System
.Standard_Library
;
998 use System
.Stack_Usage
;
1000 Bottom_Of_Stack
: aliased Integer;
1002 Task_Alternate_Stack
:
1003 aliased SSE
.Storage_Array
(1 .. Alternate_Stack_Size
);
1004 -- The alternate signal stack for this task, if any
1006 Use_Alternate_Stack
: constant Boolean := Alternate_Stack_Size
/= 0;
1007 -- Whether to use above alternate signal stack for stack overflows
1009 SEH_Table
: aliased SSE
.Storage_Array
(1 .. 8);
1010 -- Structured Exception Registration table (2 words)
1012 procedure Install_SEH_Handler
(Addr
: System
.Address
);
1013 pragma Import
(C
, Install_SEH_Handler
, "__gnat_install_SEH_handler");
1014 -- Install the SEH (Structured Exception Handling) handler
1016 Cause
: Cause_Of_Termination
:= Normal
;
1017 -- Indicates the reason why this task terminates. Normal corresponds to
1018 -- a task terminating due to completing the last statement of its body,
1019 -- or as a result of waiting on a terminate alternative. If the task
1020 -- terminates because it is being aborted then Cause will be set
1021 -- to Abnormal. If the task terminates because of an exception
1022 -- raised by the execution of its task body, then Cause is set
1023 -- to Unhandled_Exception.
1025 EO
: Exception_Occurrence
;
1026 -- If the task terminates because of an exception raised by the
1027 -- execution of its task body, then EO will contain the associated
1028 -- exception occurrence. Otherwise, it will contain Null_Occurrence.
1030 TH
: Termination_Handler
:= null;
1031 -- Pointer to the protected procedure to be executed upon task
1034 procedure Search_Fall_Back_Handler
(ID
: Task_Id
);
1035 -- Procedure that searches recursively a fall-back handler through the
1036 -- master relationship. If the handler is found, its pointer is stored
1037 -- in TH. It stops when the handler is found or when the ID is null.
1039 ------------------------------
1040 -- Search_Fall_Back_Handler --
1041 ------------------------------
1043 procedure Search_Fall_Back_Handler
(ID
: Task_Id
) is
1045 -- A null Task_Id indicates that we have reached the root of the
1046 -- task hierarchy and no handler has been found.
1051 -- If there is a fall back handler, store its pointer for later
1054 elsif ID
.Common
.Fall_Back_Handler
/= null then
1055 TH
:= ID
.Common
.Fall_Back_Handler
;
1057 -- Otherwise look for a fall back handler in the parent
1060 Search_Fall_Back_Handler
(ID
.Common
.Parent
);
1062 end Search_Fall_Back_Handler
;
1064 -- Start of processing for Task_Wrapper
1067 pragma Assert
(Self_ID
.Deferral_Level
= 1);
1070 (Self_ID
, Self_ID
.Common
.Parent
, Self_ID
.Master_Of_Task
);
1072 if Use_Alternate_Stack
then
1073 Self_ID
.Common
.Task_Alternate_Stack
:= Task_Alternate_Stack
'Address;
1076 -- Set the guard page at the bottom of the stack. The call to unprotect
1077 -- the page is done in Terminate_Task
1079 Stack_Guard
(Self_ID
, True);
1081 -- Initialize low-level TCB components, that cannot be initialized by
1082 -- the creator. Enter_Task sets Self_ID.LL.Thread.
1084 Enter_Task
(Self_ID
);
1086 -- Initialize dynamic stack usage
1088 if System
.Stack_Usage
.Is_Enabled
then
1090 Guard_Page_Size
: constant := 16 * 1024;
1091 -- Part of the stack used as a guard page. This is an OS dependent
1092 -- value, so we need to use the maximum. This value is only used
1093 -- when the stack address is known, that is currently Windows.
1095 Small_Overflow_Guard
: constant := 12 * 1024;
1096 -- Note: this used to be 4K, but was changed to 12K, since
1097 -- smaller values resulted in segmentation faults from dynamic
1100 Big_Overflow_Guard
: constant := 64 * 1024 + 8 * 1024;
1101 -- These two values are experimental, and seem to work on most
1102 -- platforms. They still need to be analyzed further. They also
1103 -- need documentation, what are they and why does the logic differ
1104 -- depending on whether the stack is large or small???
1106 Pattern_Size
: Natural :=
1107 Natural (Self_ID
.Common
.
1108 Compiler_Data
.Pri_Stack_Info
.Size
);
1109 -- Size of the pattern
1111 Stack_Base
: Address
;
1112 -- Address of the base of the stack
1115 Stack_Base
:= Self_ID
.Common
.Compiler_Data
.Pri_Stack_Info
.Base
;
1117 if Stack_Base
= Null_Address
then
1119 -- On many platforms, we don't know the real stack base
1120 -- address. Estimate it using an address in the frame.
1122 Stack_Base
:= Bottom_Of_Stack
'Address;
1124 -- Adjustments for inner frames
1126 Pattern_Size
:= Pattern_Size
-
1127 (if Pattern_Size
< Big_Overflow_Guard
1128 then Small_Overflow_Guard
1129 else Big_Overflow_Guard
);
1131 -- Reduce by the size of the final guard page
1133 Pattern_Size
:= Pattern_Size
- Guard_Page_Size
;
1138 (Self_ID
.Common
.Analyzer
,
1139 Self_ID
.Common
.Task_Image
(1 .. Self_ID
.Common
.Task_Image_Len
),
1140 Natural (Self_ID
.Common
.Compiler_Data
.Pri_Stack_Info
.Size
),
1141 SSE
.To_Integer
(Stack_Base
),
1144 Fill_Stack
(Self_ID
.Common
.Analyzer
);
1148 -- We setup the SEH (Structured Exception Handling) handler if supported
1151 Install_SEH_Handler
(SEH_Table
'Address);
1153 -- Initialize exception occurrence
1155 Save_Occurrence
(EO
, Ada
.Exceptions
.Null_Occurrence
);
1157 -- We lock RTS_Lock to wait for activator to finish activating the rest
1158 -- of the chain, so that everyone in the chain comes out in priority
1161 -- This also protects the value of
1162 -- Self_ID.Common.Activator.Common.Wait_Count.
1167 if not System
.Restrictions
.Abort_Allowed
then
1169 -- If Abort is not allowed, reset the deferral level since it will
1170 -- not get changed by the generated code. Keeping a default value
1171 -- of one would prevent some operations (e.g. select or delay) to
1172 -- proceed successfully.
1174 Self_ID
.Deferral_Level
:= 0;
1177 if Global_Task_Debug_Event_Set
then
1178 Debug
.Signal_Debug_Event
(Debug
.Debug_Event_Run
, Self_ID
);
1182 use Ada
.Task_Initialization
;
1184 Global_Initialization_Handler
: Initialization_Handler
;
1185 pragma Atomic
(Global_Initialization_Handler
);
1186 pragma Import
(Ada
, Global_Initialization_Handler
,
1187 "__gnat_global_initialization_handler");
1190 -- We are separating the following portion of the code in order to
1191 -- place the exception handlers in a different block. In this way,
1192 -- we do not call Set_Jmpbuf_Address (which needs Self) before we
1193 -- set Self in Enter_Task
1195 -- Call the initialization hook if any
1197 if Global_Initialization_Handler
/= null then
1198 Global_Initialization_Handler
.all;
1201 -- Call the task body procedure
1203 -- The task body is called with abort still deferred. That
1204 -- eliminates a dangerous window, for which we had to patch-up in
1207 -- During the expansion of the task body, we insert an RTS-call
1208 -- to Abort_Undefer, at the first point where abort should be
1211 Self_ID
.Common
.Task_Entry_Point
(Self_ID
.Common
.Task_Arg
);
1212 Initialization
.Defer_Abort_Nestable
(Self_ID
);
1215 -- We can't call Terminate_Task in the exception handlers below,
1216 -- since there may be (e.g. in the case of GCC exception handling)
1217 -- clean ups associated with the exception handler that need to
1218 -- access task specific data.
1220 -- Defer abort so that this task can't be aborted while exiting
1222 when Standard
'Abort_Signal =>
1223 Initialization
.Defer_Abort_Nestable
(Self_ID
);
1225 -- Update the cause that motivated the task termination so that
1226 -- the appropriate information is passed to the task termination
1227 -- procedure. Task termination as a result of waiting on a
1228 -- terminate alternative is a normal termination, although it is
1229 -- implemented using the abort mechanisms.
1231 if Self_ID
.Terminate_Alternative
then
1234 if Global_Task_Debug_Event_Set
then
1235 Debug
.Signal_Debug_Event
1236 (Debug
.Debug_Event_Terminated
, Self_ID
);
1241 if Global_Task_Debug_Event_Set
then
1242 Debug
.Signal_Debug_Event
1243 (Debug
.Debug_Event_Abort_Terminated
, Self_ID
);
1248 -- ??? Using an E : others here causes CD2C11A to fail on Tru64
1250 Initialization
.Defer_Abort_Nestable
(Self_ID
);
1252 -- Perform the task specific exception tracing duty. We handle
1253 -- these outputs here and not in the common notification routine
1254 -- because we need access to tasking related data and we don't
1255 -- want to drag dependencies against tasking related units in the
1256 -- the common notification units. Additionally, no trace is ever
1257 -- triggered from the common routine for the Unhandled_Raise case
1258 -- in tasks, since an exception never appears unhandled in this
1259 -- context because of this handler.
1261 if Exception_Trace
= Unhandled_Raise
then
1262 Trace_Unhandled_Exception_In_Task
(Self_ID
);
1265 -- Update the cause that motivated the task termination so that
1266 -- the appropriate information is passed to the task termination
1267 -- procedure, as well as the associated Exception_Occurrence.
1269 Cause
:= Unhandled_Exception
;
1271 Save_Occurrence
(EO
, SSL
.Get_Current_Excep
.all.all);
1273 if Global_Task_Debug_Event_Set
then
1274 Debug
.Signal_Debug_Event
1275 (Debug
.Debug_Event_Exception_Terminated
, Self_ID
);
1279 -- Look for a task termination handler. This code is for all tasks but
1280 -- the environment task. The task termination code for the environment
1281 -- task is executed by SSL.Task_Termination_Handler.
1283 Write_Lock
(Self_ID
);
1285 if Self_ID
.Common
.Specific_Handler
/= null then
1286 TH
:= Self_ID
.Common
.Specific_Handler
;
1288 -- Independent tasks should not call the Fall_Back_Handler (of the
1289 -- environment task), because they are implementation artifacts that
1290 -- should be invisible to Ada programs.
1292 elsif Self_ID
.Master_Of_Task
/= Independent_Task_Level
then
1294 -- Look for a fall-back handler following the master relationship
1295 -- for the task. As specified in ARM C.7.3 par. 9/2, "the fall-back
1296 -- handler applies only to the dependent tasks of the task". Hence,
1297 -- if the terminating tasks (Self_ID) had a fall-back handler, it
1298 -- would not apply to itself, so we start the search with the parent.
1300 Search_Fall_Back_Handler
(Self_ID
.Common
.Parent
);
1305 -- Execute the task termination handler if we found it
1309 TH
.all (Cause
, Self_ID
, EO
);
1311 -- RM-C.7.3(16) requires all exceptions raised here to be ignored
1318 if System
.Stack_Usage
.Is_Enabled
then
1319 Compute_Result
(Self_ID
.Common
.Analyzer
);
1320 Report_Result
(Self_ID
.Common
.Analyzer
);
1323 Terminate_Task
(Self_ID
);
1326 --------------------
1327 -- Terminate_Task --
1328 --------------------
1330 -- Before we allow the thread to exit, we must clean up. This is a delicate
1331 -- job. We must wake up the task's master, who may immediately try to
1332 -- deallocate the ATCB from the current task WHILE IT IS STILL EXECUTING.
1334 -- To avoid this, the parent task must be blocked up to the latest
1335 -- statement executed. The trouble is that we have another step that we
1336 -- also want to postpone to the very end, i.e., calling SSL.Destroy_TSD.
1337 -- We have to postpone that until the end because compiler-generated code
1338 -- is likely to try to access that data at just about any point.
1340 -- We can't call Destroy_TSD while we are holding any other locks, because
1341 -- it locks Global_Task_Lock, and our deadlock prevention rules require
1342 -- that to be the outermost lock. Our first "solution" was to just lock
1343 -- Global_Task_Lock in addition to the other locks, and force the parent to
1344 -- also lock this lock between its wakeup and its freeing of the ATCB. See
1345 -- Complete_Task for the parent-side of the code that has the matching
1346 -- calls to Task_Lock and Task_Unlock. That was not really a solution,
1347 -- since the operation Task_Unlock continued to access the ATCB after
1348 -- unlocking, after which the parent was observed to race ahead, deallocate
1349 -- the ATCB, and then reallocate it to another task. The call to
1350 -- Undefer_Abort in Task_Unlock by the "terminated" task was overwriting
1351 -- the data of the new task that reused the ATCB. To solve this problem, we
1352 -- introduced the new operation Final_Task_Unlock.
1354 procedure Terminate_Task
(Self_ID
: Task_Id
) is
1355 Environment_Task
: constant Task_Id
:= STPO
.Environment_Task
;
1356 Master_Of_Task
: Integer;
1357 Deallocate
: Boolean;
1360 Debug
.Task_Termination_Hook
;
1362 -- Since GCC cannot allocate stack chunks efficiently without reordering
1363 -- some of the allocations, we have to handle this unexpected situation
1364 -- here. Normally we never have to call Vulnerable_Complete_Task here.
1366 if Self_ID
.Common
.Activator
/= null then
1367 Vulnerable_Complete_Task
(Self_ID
);
1370 Initialization
.Task_Lock
(Self_ID
);
1372 Master_Of_Task
:= Self_ID
.Master_Of_Task
;
1374 -- Check if the current task is an independent task If so, decrement
1375 -- the Independent_Task_Count value.
1377 if Master_Of_Task
= Independent_Task_Level
then
1378 Write_Lock
(Environment_Task
);
1379 Utilities
.Independent_Task_Count
:=
1380 Utilities
.Independent_Task_Count
- 1;
1381 Unlock
(Environment_Task
);
1384 -- Unprotect the guard page if needed
1386 Stack_Guard
(Self_ID
, False);
1388 Utilities
.Make_Passive
(Self_ID
, Task_Completed
=> True);
1389 Deallocate
:= Self_ID
.Free_On_Termination
;
1391 pragma Assert
(Check_Exit
(Self_ID
));
1393 SSL
.Destroy_TSD
(Self_ID
.Common
.Compiler_Data
);
1394 Initialization
.Final_Task_Unlock
(Self_ID
);
1396 -- WARNING: past this point, this thread must assume that the ATCB has
1397 -- been deallocated, and can't access it anymore (which is why we have
1398 -- saved the Free_On_Termination flag in a temporary variable).
1401 Free_Task
(Self_ID
);
1404 if Master_Of_Task
> 0 then
1413 function Terminated
(T
: Task_Id
) return Boolean is
1414 Self_ID
: constant Task_Id
:= STPO
.Self
;
1418 Initialization
.Defer_Abort_Nestable
(Self_ID
);
1420 Result
:= T
.Common
.State
= Terminated
;
1422 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
1427 ----------------------------------------
1428 -- Trace_Unhandled_Exception_In_Task --
1429 ----------------------------------------
1431 procedure Trace_Unhandled_Exception_In_Task
(Self_Id
: Task_Id
) is
1432 procedure To_Stderr
(S
: String);
1433 pragma Import
(Ada
, To_Stderr
, "__gnat_to_stderr");
1435 use System
.Soft_Links
;
1437 function To_Address
is new
1438 Ada
.Unchecked_Conversion
1439 (Task_Id
, System
.Task_Primitives
.Task_Address
);
1441 Excep
: constant Exception_Occurrence_Access
:=
1442 SSL
.Get_Current_Excep
.all;
1445 -- This procedure is called by the task outermost handler in
1446 -- Task_Wrapper below, so only once the task stack has been fully
1447 -- unwound. The common notification routine has been called at the
1448 -- raise point already.
1450 -- Lock to prevent unsynchronized output
1452 Initialization
.Task_Lock
(Self_Id
);
1453 To_Stderr
("task ");
1455 if Self_Id
.Common
.Task_Image_Len
/= 0 then
1457 (Self_Id
.Common
.Task_Image
(1 .. Self_Id
.Common
.Task_Image_Len
));
1461 To_Stderr
(System
.Address_Image
(To_Address
(Self_Id
)));
1462 To_Stderr
(" terminated by unhandled exception");
1463 To_Stderr
([ASCII
.LF
]);
1464 To_Stderr
(Exception_Information
(Excep
.all));
1465 Initialization
.Task_Unlock
(Self_Id
);
1466 end Trace_Unhandled_Exception_In_Task
;
1468 ------------------------------------
1469 -- Vulnerable_Complete_Activation --
1470 ------------------------------------
1472 -- As in several other places, the locks of the activator and activated
1473 -- task are both locked here. This follows our deadlock prevention lock
1474 -- ordering policy, since the activated task must be created after the
1477 procedure Vulnerable_Complete_Activation
(Self_ID
: Task_Id
) is
1478 Activator
: constant Task_Id
:= Self_ID
.Common
.Activator
;
1481 pragma Debug
(Debug
.Trace
(Self_ID
, "V_Complete_Activation", 'C'));
1483 Write_Lock
(Activator
);
1484 Write_Lock
(Self_ID
);
1486 pragma Assert
(Self_ID
.Common
.Activator
/= null);
1488 -- Remove dangling reference to Activator, since a task may outlive its
1491 Self_ID
.Common
.Activator
:= null;
1493 -- Wake up the activator, if it is waiting for a chain of tasks to
1494 -- activate, and we are the last in the chain to complete activation.
1496 if Activator
.Common
.State
= Activator_Sleep
then
1497 Activator
.Common
.Wait_Count
:= Activator
.Common
.Wait_Count
- 1;
1499 if Activator
.Common
.Wait_Count
= 0 then
1500 Wakeup
(Activator
, Activator_Sleep
);
1504 -- The activator raises a Tasking_Error if any task it is activating
1505 -- is completed before the activation is done. However, if the reason
1506 -- for the task completion is an abort, we do not raise an exception.
1509 if not Self_ID
.Callable
1510 and then Self_ID
.Pending_ATC_Level
/= Level_Completed_Task
1512 Activator
.Common
.Activation_Failed
:= True;
1518 -- After the activation, active priority should be the same as base
1519 -- priority. We must unlock the Activator first, though, since it
1520 -- should not wait if we have lower priority.
1522 if Get_Priority
(Self_ID
) /= Self_ID
.Common
.Base_Priority
then
1523 Write_Lock
(Self_ID
);
1524 Set_Priority
(Self_ID
, Self_ID
.Common
.Base_Priority
);
1527 end Vulnerable_Complete_Activation
;
1529 --------------------------------
1530 -- Vulnerable_Complete_Master --
1531 --------------------------------
1533 procedure Vulnerable_Complete_Master
(Self_ID
: Task_Id
) is
1536 CM
: constant Master_Level
:= Self_ID
.Master_Within
;
1537 T
: aliased Task_Id
;
1539 To_Be_Freed
: Task_Id
;
1540 -- This is a list of ATCBs to be freed, after we have released all RTS
1541 -- locks. This is necessary because of the locking order rules, since
1542 -- the storage manager uses Global_Task_Lock.
1544 pragma Warnings
(Off
);
1545 function Check_Unactivated_Tasks
return Boolean;
1546 pragma Warnings
(On
);
1547 -- Temporary error-checking code below. This is part of the checks
1548 -- added in the new run time. Call it only inside a pragma Assert.
1550 -----------------------------
1551 -- Check_Unactivated_Tasks --
1552 -----------------------------
1554 function Check_Unactivated_Tasks
return Boolean is
1557 Write_Lock
(Self_ID
);
1559 C
:= All_Tasks_List
;
1560 while C
/= null loop
1561 if C
.Common
.Activator
= Self_ID
and then C
.Master_Of_Task
= CM
then
1565 if C
.Common
.Parent
= Self_ID
and then C
.Master_Of_Task
= CM
then
1568 if C
.Common
.State
= Unactivated
then
1575 C
:= C
.Common
.All_Tasks_Link
;
1582 end Check_Unactivated_Tasks
;
1584 -- Start of processing for Vulnerable_Complete_Master
1588 (Debug
.Trace
(Self_ID
, "V_Complete_Master(" & CM
'Img & ")", 'C'));
1590 pragma Assert
(Self_ID
.Common
.Wait_Count
= 0);
1592 (Self_ID
.Deferral_Level
> 0
1593 or else not System
.Restrictions
.Abort_Allowed
);
1595 -- Count how many active dependent tasks this master currently has, and
1596 -- record this in Wait_Count.
1598 -- This count should start at zero, since it is initialized to zero for
1599 -- new tasks, and the task should not exit the sleep-loops that use this
1600 -- count until the count reaches zero.
1602 -- While we're counting, if we run across any unactivated tasks that
1603 -- belong to this master, we summarily terminate them as required by
1607 Write_Lock
(Self_ID
);
1609 C
:= All_Tasks_List
;
1610 while C
/= null loop
1612 -- Terminate unactivated (never-to-be activated) tasks
1614 if C
.Common
.Activator
= Self_ID
and then C
.Master_Of_Task
= CM
then
1616 -- Usually, C.Common.Activator = Self_ID implies C.Master_Of_Task
1617 -- = CM. The only case where C is pending activation by this
1618 -- task, but the master of C is not CM is when C is part of a
1619 -- return object of a build-in-place function.
1621 pragma Assert
(C
.Common
.State
= Unactivated
);
1624 C
.Common
.Activator
:= null;
1625 C
.Common
.State
:= Terminated
;
1626 C
.Callable
:= False;
1627 Utilities
.Cancel_Queued_Entry_Calls
(C
);
1631 -- Count it if directly dependent on this master
1633 if C
.Common
.Parent
= Self_ID
and then C
.Master_Of_Task
= CM
then
1636 if C
.Awake_Count
/= 0 then
1637 Self_ID
.Common
.Wait_Count
:= Self_ID
.Common
.Wait_Count
+ 1;
1643 C
:= C
.Common
.All_Tasks_Link
;
1646 Self_ID
.Common
.State
:= Master_Completion_Sleep
;
1650 -- Wait until dependent tasks are all terminated or ready to terminate.
1651 -- While waiting, the task may be awakened if the task's priority needs
1652 -- changing, or this master is aborted. In the latter case, we abort the
1653 -- dependents, and resume waiting until Wait_Count goes to zero.
1655 Write_Lock
(Self_ID
);
1658 exit when Self_ID
.Common
.Wait_Count
= 0;
1660 -- Here is a difference as compared to Complete_Master
1662 if Self_ID
.Pending_ATC_Level
< Self_ID
.ATC_Nesting_Level
1663 and then not Self_ID
.Dependents_Aborted
1667 Abort_Dependents
(Self_ID
);
1669 Write_Lock
(Self_ID
);
1672 (Debug
.Trace
(Self_ID
, "master_completion_sleep", 'C'));
1673 Sleep
(Self_ID
, Master_Completion_Sleep
);
1677 Self_ID
.Common
.State
:= Runnable
;
1680 -- Dependents are all terminated or on terminate alternatives. Now,
1681 -- force those on terminate alternatives to terminate, by aborting them.
1683 pragma Assert
(Check_Unactivated_Tasks
);
1685 if Self_ID
.Alive_Count
> 1 then
1687 -- Consider finding a way to skip the following extra steps if there
1688 -- are no dependents with terminate alternatives. This could be done
1689 -- by adding another count to the ATCB, similar to Awake_Count, but
1690 -- keeping track of tasks that are on terminate alternatives.
1692 pragma Assert
(Self_ID
.Common
.Wait_Count
= 0);
1694 -- Force any remaining dependents to terminate by aborting them
1697 Abort_Dependents
(Self_ID
);
1699 -- Above, when we "abort" the dependents we are simply using this
1700 -- operation for convenience. We are not required to support the full
1701 -- abort-statement semantics; in particular, we are not required to
1702 -- immediately cancel any queued or in-service entry calls. That is
1703 -- good, because if we tried to cancel a call we would need to lock
1704 -- the caller, in order to wake the caller up. Our anti-deadlock
1705 -- rules prevent us from doing that without releasing the locks on C
1706 -- and Self_ID. Releasing and retaking those locks would be wasteful
1707 -- at best, and should not be considered further without more
1708 -- detailed analysis of potential concurrent accesses to the ATCBs
1709 -- of C and Self_ID.
1711 -- Count how many "alive" dependent tasks this master currently has,
1712 -- and record this in Wait_Count. This count should start at zero,
1713 -- since it is initialized to zero for new tasks, and the task should
1714 -- not exit the sleep-loops that use this count until the count
1717 pragma Assert
(Self_ID
.Common
.Wait_Count
= 0);
1719 Write_Lock
(Self_ID
);
1721 C
:= All_Tasks_List
;
1722 while C
/= null loop
1723 if C
.Common
.Parent
= Self_ID
and then C
.Master_Of_Task
= CM
then
1726 pragma Assert
(C
.Awake_Count
= 0);
1728 if C
.Alive_Count
> 0 then
1729 pragma Assert
(C
.Terminate_Alternative
);
1730 Self_ID
.Common
.Wait_Count
:= Self_ID
.Common
.Wait_Count
+ 1;
1736 C
:= C
.Common
.All_Tasks_Link
;
1739 Self_ID
.Common
.State
:= Master_Phase_2_Sleep
;
1743 -- Wait for all counted tasks to finish terminating themselves
1745 Write_Lock
(Self_ID
);
1748 exit when Self_ID
.Common
.Wait_Count
= 0;
1749 Sleep
(Self_ID
, Master_Phase_2_Sleep
);
1752 Self_ID
.Common
.State
:= Runnable
;
1756 -- We don't wake up for abort here. We are already terminating just as
1757 -- fast as we can, so there is no point.
1759 -- Remove terminated tasks from the list of Self_ID's dependents, but
1760 -- don't free their ATCBs yet, because of lock order restrictions, which
1761 -- don't allow us to call "free" or "malloc" while holding any other
1762 -- locks. Instead, we put those ATCBs to be freed onto a temporary list,
1763 -- called To_Be_Freed.
1766 C
:= All_Tasks_List
;
1768 while C
/= null loop
1770 -- If Free_On_Termination is set, do nothing here, and let the
1771 -- task free itself if not already done, otherwise we risk a race
1772 -- condition where Vulnerable_Free_Task is called in the loop below,
1773 -- while the task calls Free_Task itself, in Terminate_Task.
1775 if C
.Common
.Parent
= Self_ID
1776 and then C
.Master_Of_Task
>= CM
1777 and then not C
.Free_On_Termination
1780 P
.Common
.All_Tasks_Link
:= C
.Common
.All_Tasks_Link
;
1782 All_Tasks_List
:= C
.Common
.All_Tasks_Link
;
1785 T
:= C
.Common
.All_Tasks_Link
;
1786 C
.Common
.All_Tasks_Link
:= To_Be_Freed
;
1792 C
:= C
.Common
.All_Tasks_Link
;
1798 -- Free all the ATCBs on the list To_Be_Freed
1800 -- The ATCBs in the list are no longer in All_Tasks_List, and after
1801 -- any interrupt entries are detached from them they should no longer
1804 -- Global_Task_Lock (Task_Lock/Unlock) is locked in the loop below to
1805 -- avoid a race between a terminating task and its parent. The parent
1806 -- might try to deallocate the ACTB out from underneath the exiting
1807 -- task. Note that Free will also lock Global_Task_Lock, but that is
1808 -- OK, since this is the *one* lock for which we have a mechanism to
1809 -- support nested locking. See Task_Wrapper and its finalizer for more
1813 -- The check "T.Common.Parent /= null ..." below is to prevent dangling
1814 -- references to terminated library-level tasks, which could otherwise
1815 -- occur during finalization of library-level objects. A better solution
1816 -- might be to hook task objects into the finalization chain and
1817 -- deallocate the ATCB when the task object is deallocated. However,
1818 -- this change is not likely to gain anything significant, since all
1819 -- this storage should be recovered en-masse when the process exits.
1821 while To_Be_Freed
/= null loop
1823 To_Be_Freed
:= T
.Common
.All_Tasks_Link
;
1825 -- ??? On SGI there is currently no Interrupt_Manager, that's why we
1826 -- need to check if the Interrupt_Manager_ID is null.
1828 if T
.Interrupt_Entry
and then Interrupt_Manager_ID
/= null then
1830 Detach_Interrupt_Entries_Index
: constant Task_Entry_Index
:= 1;
1831 -- Corresponds to the entry index of System.Interrupts.
1832 -- Interrupt_Manager.Detach_Interrupt_Entries. Be sure
1833 -- to update this value when changing Interrupt_Manager specs.
1835 type Param_Type
is access all Task_Id
;
1837 Param
: aliased Param_Type
:= T
'Access;
1840 System
.Tasking
.Rendezvous
.Call_Simple
1841 (Interrupt_Manager_ID
, Detach_Interrupt_Entries_Index
,
1846 if (T
.Common
.Parent
/= null
1847 and then T
.Common
.Parent
.Common
.Parent
/= null)
1848 or else T
.Master_Of_Task
> Library_Task_Level
1850 Initialization
.Task_Lock
(Self_ID
);
1852 -- If Sec_Stack_Ptr is not null, it means that Destroy_TSD
1853 -- has not been called yet (case of an unactivated task).
1855 if T
.Common
.Compiler_Data
.Sec_Stack_Ptr
/= null then
1856 SSL
.Destroy_TSD
(T
.Common
.Compiler_Data
);
1859 Vulnerable_Free_Task
(T
);
1860 Initialization
.Task_Unlock
(Self_ID
);
1864 -- It might seem nice to let the terminated task deallocate its own
1865 -- ATCB. That would not cover the case of unactivated tasks. It also
1866 -- would force us to keep the underlying thread around past termination,
1867 -- since references to the ATCB are possible past termination.
1869 -- Currently, we get rid of the thread as soon as the task terminates,
1870 -- and let the parent recover the ATCB later.
1872 -- Some day, if we want to recover the ATCB earlier, at task
1873 -- termination, we could consider using "fat task IDs", that include the
1874 -- serial number with the ATCB pointer, to catch references to tasks
1875 -- that no longer have ATCBs. It is not clear how much this would gain,
1876 -- since the user-level task object would still be occupying storage.
1878 -- Make next master level up active. We don't need to lock the ATCB,
1879 -- since the value is only updated by each task for itself.
1881 Self_ID
.Master_Within
:= CM
- 1;
1883 Debug
.Master_Completed_Hook
(Self_ID
, CM
);
1884 end Vulnerable_Complete_Master
;
1886 ------------------------------
1887 -- Vulnerable_Complete_Task --
1888 ------------------------------
1890 -- Complete the calling task
1892 -- This procedure must be called with abort deferred. It should only be
1893 -- called by Complete_Task and Finalize_Global_Tasks (for the environment
1896 -- The effect is similar to that of Complete_Master. Differences include
1897 -- the closing of entries here, and computation of the number of active
1898 -- dependent tasks in Complete_Master.
1900 -- We don't lock Self_ID before the call to Vulnerable_Complete_Activation,
1901 -- because that does its own locking, and because we do not need the lock
1902 -- to test Self_ID.Common.Activator. That value should only be read and
1903 -- modified by Self.
1905 procedure Vulnerable_Complete_Task
(Self_ID
: Task_Id
) is
1908 (Self_ID
.Deferral_Level
> 0
1909 or else not System
.Restrictions
.Abort_Allowed
);
1910 pragma Assert
(Self_ID
= Self
);
1912 (Self_ID
.Master_Within
in
1913 Self_ID
.Master_Of_Task
.. Self_ID
.Master_Of_Task
+ 3);
1914 pragma Assert
(Self_ID
.Common
.Wait_Count
= 0);
1915 pragma Assert
(Self_ID
.Open_Accepts
= null);
1916 pragma Assert
(Self_ID
.ATC_Nesting_Level
= Level_No_ATC_Occurring
);
1918 pragma Debug
(Debug
.Trace
(Self_ID
, "V_Complete_Task", 'C'));
1920 Write_Lock
(Self_ID
);
1921 Self_ID
.Callable
:= False;
1923 -- In theory, Self should have no pending entry calls left on its
1924 -- call-stack. Each async. select statement should clean its own call,
1925 -- and blocking entry calls should defer abort until the calls are
1926 -- cancelled, then clean up.
1928 Utilities
.Cancel_Queued_Entry_Calls
(Self_ID
);
1931 if Self_ID
.Common
.Activator
/= null then
1932 Vulnerable_Complete_Activation
(Self_ID
);
1935 -- If Self_ID.Master_Within = Self_ID.Master_Of_Task + 2 we may have
1936 -- dependent tasks for which we need to wait. Otherwise we just exit.
1938 if Self_ID
.Master_Within
= Self_ID
.Master_Of_Task
+ 2 then
1939 Vulnerable_Complete_Master
(Self_ID
);
1941 end Vulnerable_Complete_Task
;
1943 --------------------------
1944 -- Vulnerable_Free_Task --
1945 --------------------------
1947 -- Recover all runtime system storage associated with the task T. This
1948 -- should only be called after T has terminated and will no longer be
1951 -- For tasks created by an allocator that fails, due to an exception, it
1952 -- is called from Expunge_Unactivated_Tasks.
1954 -- For tasks created by elaboration of task object declarations it is
1955 -- called from the finalization code of the Task_Wrapper procedure.
1957 procedure Vulnerable_Free_Task
(T
: Task_Id
) is
1959 pragma Debug
(Debug
.Trace
(Self
, "Vulnerable_Free_Task", 'C', T
));
1962 Initialization
.Finalize_Attributes
(T
);
1965 System
.Task_Primitives
.Operations
.Finalize_TCB
(T
);
1966 end Vulnerable_Free_Task
;
1968 -- Package elaboration code
1971 -- Establish the Adafinal softlink
1973 -- This is not done inside the central RTS initialization routine
1974 -- to avoid with'ing this package from System.Tasking.Initialization.
1976 SSL
.Adafinal
:= Finalize_Global_Tasks
'Access;
1978 -- Establish soft links for subprograms that manipulate master_id's.
1979 -- This cannot be done when the RTS is initialized, because of various
1980 -- elaboration constraints.
1982 SSL
.Current_Master
:= Stages
.Current_Master
'Access;
1983 SSL
.Enter_Master
:= Stages
.Enter_Master
'Access;
1984 SSL
.Complete_Master
:= Stages
.Complete_Master
'Access;
1985 end System
.Tasking
.Stages
;