1 ------------------------------------------------------------------------------
3 -- GNU ADA 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) 1992-2002, 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, 59 Temple Place - Suite 330, Boston, --
20 -- MA 02111-1307, 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. It is --
30 -- now maintained by Ada Core Technologies, Inc. (http://www.gnat.com). --
32 ------------------------------------------------------------------------------
35 -- Turn off polling, we do not want ATC polling to take place during
36 -- tasking operations. It causes infinite loops and other problems.
39 -- used for Raise_Exception
41 with System.Tasking.Debug;
42 pragma Warnings (Off, System.Tasking.Debug);
43 -- used for enabling tasking facilities with gdb
45 with System.Address_Image;
46 -- used for the function itself.
48 with System.Parameters;
53 with System.Task_Info;
54 -- used for Task_Info_Type
57 with System.Task_Primitives.Operations;
58 -- used for Finalize_Lock
68 with System.Soft_Links;
69 -- These are procedure pointers to non-tasking routines that use
70 -- task specific data. In the absence of tasking, these routines
71 -- refer to global data. In the presense of tasking, they must be
72 -- replaced with pointers to task-specific versions.
73 -- Also used for Create_TSD, Destroy_TSD, Get_Current_Excep
75 with System.Tasking.Initialization;
76 -- Used for Remove_From_All_Tasks_List
79 -- Initialization.Poll_Base_Priority_Change
80 -- Finalize_Attributes_Link
81 -- Initialize_Attributes_Link
83 pragma Elaborate_All (System.Tasking.Initialization);
84 -- This insures that tasking is initialized if any tasks are created.
86 with System.Tasking.Utilities;
87 -- Used for Make_Passive
90 with System.Tasking.Queuing;
91 -- Used for Dequeue_Head
93 with System.Tasking.Rendezvous;
94 -- Used for Call_Simple
96 with System.OS_Primitives;
97 -- Used for Delay_Modes
99 with System.Finalization_Implementation;
100 -- Used for System.Finalization_Implementation.Finalize_Global_List
103 -- Used for type Unsigned.
105 with System.Secondary_Stack;
108 with System.Storage_Elements;
109 -- used for Storage_Array;
111 with System.Standard_Library;
112 -- used for Exception_Trace
114 with System.Traces.Tasking;
115 -- used for Send_Trace_Info
117 package body System.Tasking.Stages is
119 package STPO renames System.Task_Primitives.Operations;
120 package SSL renames System.Soft_Links;
121 package SSE renames System.Storage_Elements;
122 package SST renames System.Secondary_Stack;
128 use Task_Primitives.Operations;
132 use System.Traces.Tasking;
134 -----------------------
135 -- Local Subprograms --
136 -----------------------
138 procedure Notify_Exception
140 Excep : Exception_Occurrence);
141 -- This procedure will output the task ID and the exception information,
142 -- including traceback if available.
144 procedure Task_Wrapper (Self_ID : Task_ID);
145 -- This is the procedure that is called by the GNULL from the
146 -- new context when a task is created. It waits for activation
147 -- and then calls the task body procedure. When the task body
148 -- procedure completes, it terminates the task.
150 procedure Vulnerable_Complete_Task (Self_ID : Task_ID);
151 -- Complete the calling task.
152 -- This procedure must be called with abort deferred.
153 -- It should only be called by Complete_Task and
154 -- Finalizate_Global_Tasks (for the environment task).
156 procedure Vulnerable_Complete_Master (Self_ID : Task_ID);
157 -- Complete the current master of the calling task.
158 -- This procedure must be called with abort deferred.
159 -- It should only be called by Vulnerable_Complete_Task and
162 procedure Vulnerable_Complete_Activation (Self_ID : Task_ID);
163 -- Signal to Self_ID's activator that Self_ID has
164 -- completed activation.
166 -- Call this procedure with abort deferred.
168 procedure Abort_Dependents (Self_ID : Task_ID);
169 -- Abort all the direct dependents of Self at its current master
170 -- nesting level, plus all of their dependents, transitively.
171 -- RTS_Lock should be locked by the caller.
173 procedure Vulnerable_Free_Task (T : Task_ID);
174 -- Recover all runtime system storage associated with the task T.
175 -- This should only be called after T has terminated and will no
176 -- longer be referenced.
178 -- For tasks created by an allocator that fails, due to an exception,
179 -- it is called from Expunge_Unactivated_Tasks.
181 -- It is also called from Unchecked_Deallocation, for objects that
182 -- are or contain tasks.
184 -- Different code is used at master completion, in Terminate_Dependents,
185 -- due to a need for tighter synchronization with the master.
187 procedure Terminate_Task (Self_ID : Task_ID);
188 -- Terminate the calling task.
189 -- This should only be called by the Task_Wrapper procedure.
191 ----------------------
192 -- Abort_Dependents --
193 ----------------------
195 procedure Abort_Dependents (Self_ID : Task_ID) is
203 P := C.Common.Parent;
207 -- ??? C is supposed to take care of its own dependents, so
208 -- there should be no need to worry about them. Need to double
211 if C.Master_of_Task = Self_ID.Master_Within then
212 Utilities.Abort_One_Task (Self_ID, C);
213 C.Dependents_Aborted := True;
219 P := P.Common.Parent;
222 C := C.Common.All_Tasks_Link;
225 Self_ID.Dependents_Aborted := True;
226 end Abort_Dependents;
232 procedure Abort_Tasks (Tasks : Task_List) is
234 Utilities.Abort_Tasks (Tasks);
241 -- Note that locks of activator and activated task are both locked
242 -- here. This is necessary because C.Common.State and
243 -- Self.Common.Wait_Count have to be synchronized. This is safe from
244 -- deadlock because the activator is always created before the activated
245 -- task. That satisfies our in-order-of-creation ATCB locking policy.
247 -- At one point, we may also lock the parent, if the parent is
248 -- different from the activator. That is also consistent with the
249 -- lock ordering policy, since the activator cannot be created
250 -- before the parent.
252 -- Since we are holding both the activator's lock, and Task_Wrapper
253 -- locks that before it does anything more than initialize the
254 -- low-level ATCB components, it should be safe to wait to update
255 -- the counts until we see that the thread creation is successful.
257 -- If the thread creation fails, we do need to close the entries
258 -- of the task. The first phase, of dequeuing calls, only requires
259 -- locking the acceptor's ATCB, but the waking up of the callers
260 -- requires locking the caller's ATCB. We cannot safely do this
261 -- while we are holding other locks. Therefore, the queue-clearing
262 -- operation is done in a separate pass over the activation chain.
264 procedure Activate_Tasks (Chain_Access : Activation_Chain_Access) is
265 Self_ID : constant Task_ID := STPO.Self;
268 Next_C, Last_C : Task_ID;
269 Activate_Prio : System.Any_Priority;
271 All_Elaborated : Boolean := True;
275 (Debug.Trace (Self_ID, "Activate_Tasks", 'C'));
277 Initialization.Defer_Abort_Nestable (Self_ID);
279 pragma Assert (Self_ID.Common.Wait_Count = 0);
281 -- Lock RTS_Lock, to prevent activated tasks
282 -- from racing ahead before we finish activating the chain.
286 -- Check that all task bodies have been elaborated.
288 C := Chain_Access.T_ID;
292 if C.Common.Elaborated /= null
293 and then not C.Common.Elaborated.all
295 All_Elaborated := False;
298 -- Reverse the activation chain so that tasks are
299 -- activated in the same order they're declared.
301 Next_C := C.Common.Activation_Link;
302 C.Common.Activation_Link := Last_C;
307 Chain_Access.T_ID := Last_C;
309 if not All_Elaborated then
311 Initialization.Undefer_Abort_Nestable (Self_ID);
313 (Program_Error'Identity, "Some tasks have not been elaborated");
316 -- Activate all the tasks in the chain.
317 -- Creation of the thread of control was deferred until
318 -- activation. So create it now.
320 C := Chain_Access.T_ID;
323 if C.Common.State /= Terminated then
324 pragma Assert (C.Common.State = Unactivated);
326 P := C.Common.Parent;
330 if C.Common.Base_Priority < Get_Priority (Self_ID) then
331 Activate_Prio := Get_Priority (Self_ID);
333 Activate_Prio := C.Common.Base_Priority;
336 System.Task_Primitives.Operations.Create_Task
337 (C, Task_Wrapper'Address,
339 (C.Common.Compiler_Data.Pri_Stack_Info.Size),
340 Activate_Prio, Success);
342 -- There would be a race between the created task and
343 -- the creator to do the following initialization,
344 -- if we did not have a Lock/Unlock_RTS pair
345 -- in the task wrapper, to prevent it from racing ahead.
348 C.Common.State := Runnable;
351 P.Awake_Count := P.Awake_Count + 1;
352 P.Alive_Count := P.Alive_Count + 1;
354 if P.Common.State = Master_Completion_Sleep and then
355 C.Master_of_Task = P.Master_Within
357 pragma Assert (Self_ID /= P);
358 P.Common.Wait_Count := P.Common.Wait_Count + 1;
365 -- No need to set Awake_Count, State, etc. here since the loop
366 -- below will do that for any Unactivated tasks.
370 Self_ID.Common.Activation_Failed := True;
374 C := C.Common.Activation_Link;
377 if not Single_Lock then
381 -- Close the entries of any tasks that failed thread creation,
382 -- and count those that have not finished activation.
384 Write_Lock (Self_ID);
385 Self_ID.Common.State := Activator_Sleep;
387 C := Chain_Access.T_ID;
391 if C.Common.State = Unactivated then
392 C.Common.Activator := null;
393 C.Common.State := Terminated;
395 Utilities.Cancel_Queued_Entry_Calls (C);
397 elsif C.Common.Activator /= null then
398 Self_ID.Common.Wait_Count := Self_ID.Common.Wait_Count + 1;
402 P := C.Common.Activation_Link;
403 C.Common.Activation_Link := null;
407 -- Wait for the activated tasks to complete activation.
408 -- It is unsafe to abort any of these tasks until the count goes to
412 Initialization.Poll_Base_Priority_Change (Self_ID);
413 exit when Self_ID.Common.Wait_Count = 0;
414 Sleep (Self_ID, Activator_Sleep);
417 Self_ID.Common.State := Runnable;
424 -- Remove the tasks from the chain.
426 Chain_Access.T_ID := null;
427 Initialization.Undefer_Abort_Nestable (Self_ID);
429 if Self_ID.Common.Activation_Failed then
430 Self_ID.Common.Activation_Failed := False;
431 Raise_Exception (Tasking_Error'Identity,
432 "Failure during activation");
436 -------------------------
437 -- Complete_Activation --
438 -------------------------
440 procedure Complete_Activation is
441 Self_ID : constant Task_ID := STPO.Self;
443 Initialization.Defer_Abort_Nestable (Self_ID);
449 Vulnerable_Complete_Activation (Self_ID);
455 Initialization.Undefer_Abort_Nestable (Self_ID);
458 -- Why do we need to allow for nested deferral here?
460 if Runtime_Traces then
461 Send_Trace_Info (T_Activate);
463 end Complete_Activation;
465 ---------------------
466 -- Complete_Master --
467 ---------------------
469 procedure Complete_Master is
470 Self_ID : Task_ID := STPO.Self;
473 pragma Assert (Self_ID.Deferral_Level > 0);
475 Vulnerable_Complete_Master (Self_ID);
482 -- See comments on Vulnerable_Complete_Task for details.
484 procedure Complete_Task is
485 Self_ID : constant Task_ID := STPO.Self;
487 pragma Assert (Self_ID.Deferral_Level > 0);
489 Vulnerable_Complete_Task (Self_ID);
491 -- All of our dependents have terminated.
492 -- Never undefer abort again!
499 -- Compiler interface only. Do not call from within the RTS.
500 -- This must be called to create a new task.
502 procedure Create_Task
504 Size : System.Parameters.Size_Type;
505 Task_Info : System.Task_Info.Task_Info_Type;
506 Num_Entries : Task_Entry_Index;
507 Master : Master_Level;
508 State : Task_Procedure_Access;
509 Discriminants : System.Address;
510 Elaborated : Access_Boolean;
511 Chain : in out Activation_Chain;
512 Task_Image : System.Task_Info.Task_Image_Type;
513 Created_Task : out Task_ID)
516 Self_ID : constant Task_ID := STPO.Self;
518 Base_Priority : System.Any_Priority;
522 (Debug.Trace (Self_ID, "Create_Task", 'C'));
524 if Priority = Unspecified_Priority then
525 Base_Priority := Self_ID.Common.Base_Priority;
527 Base_Priority := System.Any_Priority (Priority);
530 -- Find parent P of new Task, via master level number.
535 while P.Master_of_Task >= Master loop
536 P := P.Common.Parent;
541 Initialization.Defer_Abort_Nestable (Self_ID);
544 T := New_ATCB (Num_Entries);
548 Initialization.Undefer_Abort_Nestable (Self_ID);
549 Raise_Exception (Storage_Error'Identity, "Cannot allocate task");
552 -- RTS_Lock is used by Abort_Dependents and Abort_Tasks.
553 -- Up to this point, it is possible that we may be part of
554 -- a family of tasks that is being aborted.
557 Write_Lock (Self_ID);
559 -- Now, we must check that we have not been aborted.
560 -- If so, we should give up on creating this task,
561 -- and simply return.
563 if not Self_ID.Callable then
564 pragma Assert (Self_ID.Pending_ATC_Level = 0);
565 pragma Assert (Self_ID.Pending_Action);
566 pragma Assert (Chain.T_ID = null
567 or else Chain.T_ID.Common.State = Unactivated);
571 Initialization.Undefer_Abort_Nestable (Self_ID);
573 -- ??? Should never get here
575 pragma Assert (False);
576 raise Standard'Abort_Signal;
579 Initialize_ATCB (Self_ID, State, Discriminants, P, Elaborated,
580 Base_Priority, Task_Info, Size, T, Success);
585 Initialization.Undefer_Abort_Nestable (Self_ID);
587 (Storage_Error'Identity, "Failed to initialize task");
590 T.Master_of_Task := Master;
591 T.Master_Within := T.Master_of_Task + 1;
593 for L in T.Entry_Calls'Range loop
594 T.Entry_Calls (L).Self := T;
595 T.Entry_Calls (L).Level := L;
598 T.Common.Task_Image := Task_Image;
602 -- Create TSD as early as possible in the creation of a task, since it
603 -- may be used by the operation of Ada code within the task.
605 SSL.Create_TSD (T.Common.Compiler_Data);
606 T.Common.Activation_Link := Chain.T_ID;
608 Initialization.Initialize_Attributes_Link.all (T);
610 Initialization.Undefer_Abort_Nestable (Self_ID);
612 if Runtime_Traces then
613 Send_Trace_Info (T_Create, T);
621 function Current_Master return Master_Level is
623 return STPO.Self.Master_Within;
630 procedure Enter_Master is
631 Self_ID : constant Task_ID := STPO.Self;
634 Self_ID.Master_Within := Self_ID.Master_Within + 1;
637 -------------------------------
638 -- Expunge_Unactivated_Tasks --
639 -------------------------------
641 -- See procedure Close_Entries for the general case.
643 procedure Expunge_Unactivated_Tasks (Chain : in out Activation_Chain) is
644 Self_ID : constant Task_ID := STPO.Self;
646 Call : Entry_Call_Link;
651 (Debug.Trace (Self_ID, "Expunge_Unactivated_Tasks", 'C'));
653 Initialization.Defer_Abort_Nestable (Self_ID);
656 -- Experimentation has shown that abort is sometimes (but not
657 -- always) already deferred when this is called.
658 -- That may indicate an error. Find out what is going on.
663 pragma Assert (C.Common.State = Unactivated);
665 Temp := C.Common.Activation_Link;
667 if C.Common.State = Unactivated then
671 for J in 1 .. C.Entry_Num loop
672 Queuing.Dequeue_Head (C.Entry_Queues (J), Call);
673 pragma Assert (Call = null);
678 Initialization.Remove_From_All_Tasks_List (C);
681 Vulnerable_Free_Task (C);
687 Initialization.Undefer_Abort_Nestable (Self_ID);
688 end Expunge_Unactivated_Tasks;
690 ---------------------------
691 -- Finalize_Global_Tasks --
692 ---------------------------
695 -- We have a potential problem here if finalization of global
696 -- objects does anything with signals or the timer server, since
697 -- by that time those servers have terminated.
699 -- It is hard to see how that would occur.
701 -- However, a better solution might be to do all this finalization
702 -- using the global finalization chain.
704 procedure Finalize_Global_Tasks is
705 Self_ID : constant Task_ID := STPO.Self;
709 if Self_ID.Deferral_Level = 0 then
711 -- In principle, we should be able to predict whether
712 -- abort is already deferred here (and it should not be deferred
713 -- yet but in practice it seems Finalize_Global_Tasks is being
714 -- called sometimes, from RTS code for exceptions, with abort already
717 Initialization.Defer_Abort_Nestable (Self_ID);
719 -- Never undefer again!!!
722 -- This code is only executed by the environment task
724 pragma Assert (Self_ID = Environment_Task);
726 -- Set Environment_Task'Callable to false to notify library-level tasks
727 -- that it is waiting for them (cf 5619-003).
729 Self_ID.Callable := False;
731 -- Exit level 2 master, for normal tasks in library-level packages.
735 -- Force termination of "independent" library-level server tasks.
739 Abort_Dependents (Self_ID);
741 if not Single_Lock then
745 -- We need to explicitly wait for the task to be
746 -- terminated here because on true concurrent system, we
747 -- may end this procedure before the tasks are really
750 Write_Lock (Self_ID);
753 exit when Utilities.Independent_Task_Count = 0;
755 -- We used to yield here, but this did not take into account
756 -- low priority tasks that would cause dead lock in some cases.
760 (Self_ID, 0.01, System.OS_Primitives.Relative,
761 Self_ID.Common.State, Ignore, Ignore);
764 -- ??? On multi-processor environments, it seems that the above loop
765 -- isn't sufficient, so we need to add an additional delay.
768 (Self_ID, 0.01, System.OS_Primitives.Relative,
769 Self_ID.Common.State, Ignore, Ignore);
777 -- Complete the environment task.
779 Vulnerable_Complete_Task (Self_ID);
781 System.Finalization_Implementation.Finalize_Global_List;
783 SSL.Abort_Defer := SSL.Abort_Defer_NT'Access;
784 SSL.Abort_Undefer := SSL.Abort_Undefer_NT'Access;
785 SSL.Lock_Task := SSL.Task_Lock_NT'Access;
786 SSL.Unlock_Task := SSL.Task_Unlock_NT'Access;
787 SSL.Get_Jmpbuf_Address := SSL.Get_Jmpbuf_Address_NT'Access;
788 SSL.Set_Jmpbuf_Address := SSL.Set_Jmpbuf_Address_NT'Access;
789 SSL.Get_Sec_Stack_Addr := SSL.Get_Sec_Stack_Addr_NT'Access;
790 SSL.Set_Sec_Stack_Addr := SSL.Set_Sec_Stack_Addr_NT'Access;
791 SSL.Get_Exc_Stack_Addr := SSL.Get_Exc_Stack_Addr_NT'Access;
792 SSL.Set_Exc_Stack_Addr := SSL.Set_Exc_Stack_Addr_NT'Access;
793 SSL.Check_Abort_Status := SSL.Check_Abort_Status_NT'Access;
794 SSL.Get_Stack_Info := SSL.Get_Stack_Info_NT'Access;
796 -- Don't bother trying to finalize Initialization.Global_Task_Lock
797 -- and System.Task_Primitives.RTS_Lock.
799 end Finalize_Global_Tasks;
805 procedure Free_Task (T : Task_ID) is
806 Self_Id : constant Task_ID := Self;
809 if T.Common.State = Terminated then
810 -- It is not safe to call Abort_Defer or Write_Lock at this stage
812 Initialization.Task_Lock (Self_Id);
814 if T.Common.Task_Image /= null then
815 Free_Task_Image (T.Common.Task_Image);
819 Initialization.Remove_From_All_Tasks_List (T);
822 Initialization.Task_Unlock (Self_Id);
824 System.Task_Primitives.Operations.Finalize_TCB (T);
826 -- If the task is not terminated, then we simply ignore the call. This
827 -- happens when a user program attempts an unchecked deallocation on
828 -- a non-terminated task.
835 ----------------------
836 -- Notify_Exception --
837 ----------------------
839 procedure Notify_Exception
841 Excep : Exception_Occurrence)
843 procedure To_Stderr (S : String);
844 pragma Import (Ada, To_Stderr, "__gnat_to_stderr");
846 use System.Task_Info;
847 use System.Soft_Links;
849 function To_Address is new
850 Unchecked_Conversion (Task_ID, System.Address);
852 function Tailored_Exception_Information
853 (E : Exception_Occurrence) return String;
855 (Ada, Tailored_Exception_Information,
856 "__gnat_tailored_exception_information");
861 if Self_Id.Common.Task_Image /= null then
862 To_Stderr (Self_Id.Common.Task_Image.all);
866 To_Stderr (System.Address_Image (To_Address (Self_Id)));
867 To_Stderr (" terminated by unhandled exception");
868 To_Stderr ((1 => ASCII.LF));
869 To_Stderr (Tailored_Exception_Information (Excep));
870 end Notify_Exception;
876 -- The task wrapper is a procedure that is called first for each task
877 -- task body, and which in turn calls the compiler-generated task body
878 -- procedure. The wrapper's main job is to do initialization for the task.
879 -- It also has some locally declared objects that server as per-task local
880 -- data. Task finalization is done by Complete_Task, which is called from
881 -- an at-end handler that the compiler generates.
883 -- The variable ID in the task wrapper is used to implement the Self
884 -- function on targets where there is a fast way to find the stack base
885 -- of the current thread, since it should be at a fixed offset from the
888 -- The variable Magic_Number is also used in such implementations
889 -- of Self, to check whether the current task is an Ada task, as
890 -- compared to other-language threads.
892 -- Both act as constants, once initialized, but need to be marked as
893 -- volatile or aliased to prevent the compiler from optimizing away the
894 -- storage. See System.Task_Primitives.Operations.Self for more info.
896 procedure Task_Wrapper (Self_ID : Task_ID) is
897 ID : Task_ID := Self_ID;
898 pragma Volatile (ID);
899 -- Do not delete this variable.
900 -- In some targets, we need this variable to implement a fast Self.
902 Magic_Number : Interfaces.C.unsigned := 16#ADAADAAD#;
903 pragma Volatile (Magic_Number);
904 -- We use this to verify that we are looking at an Ada task,
905 -- inside of System.Task_Primitives.Operations.Self.
907 use type System.Parameters.Size_Type;
908 use type SSE.Storage_Offset;
909 use System.Standard_Library;
911 Secondary_Stack : aliased SSE.Storage_Array
912 (1 .. ID.Common.Compiler_Data.Pri_Stack_Info.Size *
913 SSE.Storage_Offset (Parameters.Sec_Stack_Ratio) / 100);
914 Secondary_Stack_Address : System.Address := Secondary_Stack'Address;
917 pragma Assert (Self_ID.Deferral_Level = 1);
919 if not Parameters.Sec_Stack_Dynamic then
920 ID.Common.Compiler_Data.Sec_Stack_Addr := Secondary_Stack'Address;
921 SST.SS_Init (Secondary_Stack_Address, Integer (Secondary_Stack'Last));
924 -- Set the guard page at the bottom of the stack.
925 -- The call to unprotect the page is done in Terminate_Task
927 Stack_Guard (Self_ID, True);
929 -- Initialize low-level TCB components, that
930 -- cannot be initialized by the creator.
931 -- Enter_Task sets Self_ID.Known_Tasks_Index
932 -- and Self_ID.LL.Thread
934 Enter_Task (Self_ID);
936 -- We lock RTS_Lock to wait for activator to finish activating
937 -- the rest of the chain, so that everyone in the chain comes out
938 -- in priority order.
939 -- This also protects the value of
940 -- Self_ID.Common.Activator.Common.Wait_Count.
946 -- We are separating the following portion of the code in order to
947 -- place the exception handlers in a different block.
948 -- In this way we do not call Set_Jmpbuf_Address (which needs
949 -- Self) before we set Self in Enter_Task
951 -- Call the task body procedure.
953 -- The task body is called with abort still deferred. That
954 -- eliminates a dangerous window, for which we had to patch-up in
956 -- During the expansion of the task body, we insert an RTS-call
957 -- to Abort_Undefer, at the first point where abort should be
960 Self_ID.Common.Task_Entry_Point (Self_ID.Common.Task_Arg);
961 Terminate_Task (Self_ID);
964 when Standard'Abort_Signal =>
965 Terminate_Task (Self_ID);
968 -- ??? Using an E : others here causes CD2C11A to fail on
969 -- DEC Unix, see 7925-005.
971 if Exception_Trace = Unhandled_Raise then
972 Notify_Exception (Self_ID, SSL.Get_Current_Excep.all.all);
975 Terminate_Task (Self_ID);
983 -- Before we allow the thread to exit, we must clean up. This is a
984 -- a delicate job. We must wake up the task's master, who may immediately
985 -- try to deallocate the ATCB out from under the current task WHILE IT IS
988 -- To avoid this, the parent task must be blocked up to the last thing
989 -- done before the call to Exit_Task. The trouble is that we have another
990 -- step that we also want to postpone to the very end, i.e., calling
991 -- SSL.Destroy_TSD. We have to postpone that until the end because
992 -- compiler-generated code is likely to try to access that data at just
995 -- We can't call Destroy_TSD while we are holding any other locks, because
996 -- it locks Global_Task_Lock, and our deadlock prevention rules require
997 -- that to be the outermost lock. Our first "solution" was to just lock
998 -- Global_Task_Lock in addition to the other locks, and force the parent
999 -- to also lock this lock between its wakeup and its freeing of the ATCB.
1000 -- See Complete_Task for the parent-side of the code that has the matching
1001 -- calls to Task_Lock and Task_Unlock. That was not really a solution,
1002 -- since the operation Task_Unlock continued to access the ATCB after
1003 -- unlocking, after which the parent was observed to race ahead,
1004 -- deallocate the ATCB, and then reallocate it to another task. The
1005 -- call to Undefer_Abortion in Task_Unlock by the "terminated" task was
1006 -- overwriting the data of the new task that reused the ATCB! To solve
1007 -- this problem, we introduced the new operation Final_Task_Unlock.
1009 procedure Terminate_Task (Self_ID : Task_ID) is
1010 Environment_Task : constant Task_ID := STPO.Environment_Task;
1013 if Runtime_Traces then
1014 Send_Trace_Info (T_Terminate);
1017 -- Since GCC cannot allocate stack chunks efficiently without reordering
1018 -- some of the allocations, we have to handle this unexpected situation
1019 -- here. We should normally never have to call Vulnerable_Complete_Task
1020 -- here. See 6602-003 for more details.
1022 if Self_ID.Common.Activator /= null then
1023 Vulnerable_Complete_Task (Self_ID);
1026 Initialization.Task_Lock (Self_ID);
1032 -- Check if the current task is an independent task
1033 -- If so, decrement the Independent_Task_Count value.
1035 if Self_ID.Master_of_Task = 2 then
1037 Utilities.Independent_Task_Count :=
1038 Utilities.Independent_Task_Count - 1;
1041 Write_Lock (Environment_Task);
1042 Utilities.Independent_Task_Count :=
1043 Utilities.Independent_Task_Count - 1;
1044 Unlock (Environment_Task);
1048 -- Unprotect the guard page if needed.
1050 Stack_Guard (Self_ID, False);
1052 Utilities.Make_Passive (Self_ID, Task_Completed => True);
1058 pragma Assert (Check_Exit (Self_ID));
1060 SSL.Destroy_TSD (Self_ID.Common.Compiler_Data);
1061 Initialization.Final_Task_Unlock (Self_ID);
1064 -- past this point, this thread must assume that the ATCB
1065 -- has been deallocated. It should not be accessed again.
1074 function Terminated (T : Task_ID) return Boolean is
1076 Self_ID : Task_ID := STPO.Self;
1079 Initialization.Defer_Abort_Nestable (Self_ID);
1086 Result := T.Common.State = Terminated;
1093 Initialization.Undefer_Abort_Nestable (Self_ID);
1097 ------------------------------------
1098 -- Vulnerable_Complete_Activation --
1099 ------------------------------------
1101 -- As in several other places, the locks of the activator and activated
1102 -- task are both locked here. This follows our deadlock prevention lock
1103 -- ordering policy, since the activated task must be created after the
1106 procedure Vulnerable_Complete_Activation (Self_ID : Task_ID) is
1107 Activator : constant Task_ID := Self_ID.Common.Activator;
1110 pragma Debug (Debug.Trace (Self_ID, "V_Complete_Activation", 'C'));
1112 Write_Lock (Activator);
1113 Write_Lock (Self_ID);
1115 pragma Assert (Self_ID.Common.Activator /= null);
1117 -- Remove dangling reference to Activator,
1118 -- since a task may outlive its activator.
1120 Self_ID.Common.Activator := null;
1122 -- Wake up the activator, if it is waiting for a chain
1123 -- of tasks to activate, and we are the last in the chain
1124 -- to complete activation
1126 if Activator.Common.State = Activator_Sleep then
1127 Activator.Common.Wait_Count := Activator.Common.Wait_Count - 1;
1129 if Activator.Common.Wait_Count = 0 then
1130 Wakeup (Activator, Activator_Sleep);
1134 -- The activator raises a Tasking_Error if any task
1135 -- it is activating is completed before the activation is
1136 -- done. However, if the reason for the task completion is
1137 -- an abortion, we do not raise an exception. ARM 9.2(5).
1139 if not Self_ID.Callable and then Self_ID.Pending_ATC_Level /= 0 then
1140 Activator.Common.Activation_Failed := True;
1146 -- After the activation, active priority should be the same
1147 -- as base priority. We must unlock the Activator first,
1148 -- though, since it should not wait if we have lower priority.
1150 if Get_Priority (Self_ID) /= Self_ID.Common.Base_Priority then
1151 Write_Lock (Self_ID);
1152 Set_Priority (Self_ID, Self_ID.Common.Base_Priority);
1155 end Vulnerable_Complete_Activation;
1157 --------------------------------
1158 -- Vulnerable_Complete_Master --
1159 --------------------------------
1161 procedure Vulnerable_Complete_Master (Self_ID : Task_ID) is
1164 CM : Master_Level := Self_ID.Master_Within;
1165 T : aliased Task_ID;
1167 To_Be_Freed : Task_ID;
1168 -- This is a list of ATCBs to be freed, after we have released
1169 -- all RTS locks. This is necessary because of the locking order
1170 -- rules, since the storage manager uses Global_Task_Lock.
1172 pragma Warnings (Off);
1173 function Check_Unactivated_Tasks return Boolean;
1174 pragma Warnings (On);
1175 -- Temporary error-checking code below. This is part of the checks
1176 -- added in the new run time. Call it only inside a pragma Assert.
1178 -----------------------------
1179 -- Check_Unactivated_Tasks --
1180 -----------------------------
1182 function Check_Unactivated_Tasks return Boolean is
1184 if not Single_Lock then
1188 Write_Lock (Self_ID);
1189 C := All_Tasks_List;
1191 while C /= null loop
1192 if C.Common.Activator = Self_ID then
1196 if C.Common.Parent = Self_ID and then C.Master_of_Task = CM then
1199 if C.Common.State = Unactivated then
1206 C := C.Common.All_Tasks_Link;
1211 if not Single_Lock then
1216 end Check_Unactivated_Tasks;
1218 -- Start of processing for Vulnerable_Complete_Master
1222 (Debug.Trace (Self_ID, "V_Complete_Master", 'C'));
1224 pragma Assert (Self_ID.Common.Wait_Count = 0);
1225 pragma Assert (Self_ID.Deferral_Level > 0);
1227 -- Count how many active dependent tasks this master currently
1228 -- has, and record this in Wait_Count.
1230 -- This count should start at zero, since it is initialized to
1231 -- zero for new tasks, and the task should not exit the
1232 -- sleep-loops that use this count until the count reaches zero.
1235 Write_Lock (Self_ID);
1236 C := All_Tasks_List;
1238 while C /= null loop
1239 if C.Common.Activator = Self_ID then
1240 pragma Assert (C.Common.State = Unactivated);
1243 C.Common.Activator := null;
1244 C.Common.State := Terminated;
1245 C.Callable := False;
1246 Utilities.Cancel_Queued_Entry_Calls (C);
1250 if C.Common.Parent = Self_ID and then C.Master_of_Task = CM then
1253 if C.Awake_Count /= 0 then
1254 Self_ID.Common.Wait_Count := Self_ID.Common.Wait_Count + 1;
1260 C := C.Common.All_Tasks_Link;
1263 Self_ID.Common.State := Master_Completion_Sleep;
1266 if not Single_Lock then
1270 -- Wait until dependent tasks are all terminated or ready to terminate.
1271 -- While waiting, the task may be awakened if the task's priority needs
1272 -- changing, or this master is aborted. In the latter case, we want
1273 -- to abort the dependents, and resume waiting until Wait_Count goes
1276 Write_Lock (Self_ID);
1279 Initialization.Poll_Base_Priority_Change (Self_ID);
1280 exit when Self_ID.Common.Wait_Count = 0;
1282 -- Here is a difference as compared to Complete_Master
1284 if Self_ID.Pending_ATC_Level < Self_ID.ATC_Nesting_Level
1285 and then not Self_ID.Dependents_Aborted
1288 Abort_Dependents (Self_ID);
1292 Abort_Dependents (Self_ID);
1294 Write_Lock (Self_ID);
1297 Sleep (Self_ID, Master_Completion_Sleep);
1301 Self_ID.Common.State := Runnable;
1304 -- Dependents are all terminated or on terminate alternatives.
1305 -- Now, force those on terminate alternatives to terminate, by
1308 pragma Assert (Check_Unactivated_Tasks);
1310 if Self_ID.Alive_Count > 1 then
1312 -- Consider finding a way to skip the following extra steps if there
1313 -- are no dependents with terminate alternatives. This could be done
1314 -- by adding another count to the ATCB, similar to Awake_Count, but
1315 -- keeping track of tasks that are on terminate alternatives.
1317 pragma Assert (Self_ID.Common.Wait_Count = 0);
1319 -- Force any remaining dependents to terminate, by aborting them.
1321 if not Single_Lock then
1325 Abort_Dependents (Self_ID);
1327 -- Above, when we "abort" the dependents we are simply using this
1328 -- operation for convenience. We are not required to support the full
1329 -- abort-statement semantics; in particular, we are not required to
1330 -- immediately cancel any queued or in-service entry calls. That is
1331 -- good, because if we tried to cancel a call we would need to lock
1332 -- the caller, in order to wake the caller up. Our anti-deadlock
1333 -- rules prevent us from doing that without releasing the locks on C
1334 -- and Self_ID. Releasing and retaking those locks would be wasteful
1335 -- at best, and should not be considered further without more
1336 -- detailed analysis of potential concurrent accesses to the
1337 -- ATCBs of C and Self_ID.
1339 -- Count how many "alive" dependent tasks this master currently
1340 -- has, and record this in Wait_Count. This count should start at
1341 -- zero, since it is initialized to zero for new tasks, and the
1342 -- task should not exit the sleep-loops that use this count until
1343 -- the count reaches zero.
1345 pragma Assert (Self_ID.Common.Wait_Count = 0);
1347 Write_Lock (Self_ID);
1348 C := All_Tasks_List;
1350 while C /= null loop
1351 if C.Common.Parent = Self_ID and then C.Master_of_Task = CM then
1354 pragma Assert (C.Awake_Count = 0);
1356 if C.Alive_Count > 0 then
1357 pragma Assert (C.Terminate_Alternative);
1358 Self_ID.Common.Wait_Count := Self_ID.Common.Wait_Count + 1;
1364 C := C.Common.All_Tasks_Link;
1367 Self_ID.Common.State := Master_Phase_2_Sleep;
1370 if not Single_Lock then
1374 -- Wait for all counted tasks to finish terminating themselves.
1376 Write_Lock (Self_ID);
1379 Initialization.Poll_Base_Priority_Change (Self_ID);
1380 exit when Self_ID.Common.Wait_Count = 0;
1381 Sleep (Self_ID, Master_Phase_2_Sleep);
1384 Self_ID.Common.State := Runnable;
1388 -- We don't wake up for abortion here. We are already terminating
1389 -- just as fast as we can, so there is no point.
1391 -- Remove terminated tasks from the list of Self_ID's dependents, but
1392 -- don't free their ATCBs yet, because of lock order restrictions,
1393 -- which don't allow us to call "free" or "malloc" while holding any
1394 -- other locks. Instead, we put those ATCBs to be freed onto a
1395 -- temporary list, called To_Be_Freed.
1397 if not Single_Lock then
1401 C := All_Tasks_List;
1404 while C /= null loop
1405 if C.Common.Parent = Self_ID and then C.Master_of_Task >= CM then
1407 P.Common.All_Tasks_Link := C.Common.All_Tasks_Link;
1409 All_Tasks_List := C.Common.All_Tasks_Link;
1412 T := C.Common.All_Tasks_Link;
1413 C.Common.All_Tasks_Link := To_Be_Freed;
1419 C := C.Common.All_Tasks_Link;
1425 -- Free all the ATCBs on the list To_Be_Freed.
1427 -- The ATCBs in the list are no longer in All_Tasks_List, and after
1428 -- any interrupt entries are detached from them they should no longer
1431 -- Global_Task_Lock (Task_Lock/Unlock) is locked in the loop below to
1432 -- avoid a race between a terminating task and its parent. The parent
1433 -- might try to deallocate the ACTB out from underneath the exiting
1434 -- task. Note that Free will also lock Global_Task_Lock, but that is
1435 -- OK, since this is the *one* lock for which we have a mechanism to
1436 -- support nested locking. See Task_Wrapper and its finalizer for more
1440 -- The check "T.Common.Parent /= null ..." below is to prevent dangling
1441 -- references to terminated library-level tasks, which could
1442 -- otherwise occur during finalization of library-level objects.
1443 -- A better solution might be to hook task objects into the
1444 -- finalization chain and deallocate the ATCB when the task
1445 -- object is deallocated. However, this change is not likely
1446 -- to gain anything significant, since all this storage should
1447 -- be recovered en-masse when the process exits.
1449 while To_Be_Freed /= null loop
1451 To_Be_Freed := T.Common.All_Tasks_Link;
1453 -- ??? On SGI there is currently no Interrupt_Manager, that's
1454 -- why we need to check if the Interrupt_Manager_ID is null
1456 if T.Interrupt_Entry and Interrupt_Manager_ID /= null then
1458 Detach_Interrupt_Entries_Index : Task_Entry_Index := 1;
1459 -- Corresponds to the entry index of System.Interrupts.
1460 -- Interrupt_Manager.Detach_Interrupt_Entries.
1461 -- Be sure to update this value when changing
1462 -- Interrupt_Manager specs.
1464 type Param_Type is access all Task_ID;
1466 Param : aliased Param_Type := T'Access;
1469 System.Tasking.Rendezvous.Call_Simple
1470 (Interrupt_Manager_ID, Detach_Interrupt_Entries_Index,
1475 if (T.Common.Parent /= null
1476 and then T.Common.Parent.Common.Parent /= null)
1477 or else T.Master_of_Task > 3
1479 Initialization.Task_Lock (Self_ID);
1481 -- If Sec_Stack_Addr is not null, it means that Destroy_TSD
1482 -- has not been called yet (case of an unactivated task).
1484 if T.Common.Compiler_Data.Sec_Stack_Addr /= Null_Address then
1485 SSL.Destroy_TSD (T.Common.Compiler_Data);
1488 Vulnerable_Free_Task (T);
1489 Initialization.Task_Unlock (Self_ID);
1493 -- It might seem nice to let the terminated task deallocate its own
1494 -- ATCB. That would not cover the case of unactivated tasks. It also
1495 -- would force us to keep the underlying thread around past termination,
1496 -- since references to the ATCB are possible past termination.
1497 -- Currently, we get rid of the thread as soon as the task terminates,
1498 -- and let the parent recover the ATCB later.
1500 -- Some day, if we want to recover the ATCB earlier, at task
1501 -- termination, we could consider using "fat task IDs", that include the
1502 -- serial number with the ATCB pointer, to catch references to tasks
1503 -- that no longer have ATCBs. It is not clear how much this would gain,
1504 -- since the user-level task object would still be occupying storage.
1506 -- Make next master level up active.
1507 -- We don't need to lock the ATCB, since the value is only updated by
1508 -- each task for itself.
1510 Self_ID.Master_Within := CM - 1;
1511 end Vulnerable_Complete_Master;
1513 ------------------------------
1514 -- Vulnerable_Complete_Task --
1515 ------------------------------
1517 -- Complete the calling task
1519 -- This procedure must be called with abort deferred. (That's why the
1520 -- name has "Vulnerable" in it.) It should only be called by Complete_Task
1521 -- and Finalize_Global_Tasks (for the environment task).
1523 -- The effect is similar to that of Complete_Master. Differences include
1524 -- the closing of entries here, and computation of the number of active
1525 -- dependent tasks in Complete_Master.
1527 -- We don't lock Self_ID before the call to Vulnerable_Complete_Activation,
1528 -- because that does its own locking, and because we do not need the lock
1529 -- to test Self_ID.Common.Activator. That value should only be read and
1530 -- modified by Self.
1532 procedure Vulnerable_Complete_Task (Self_ID : Task_ID) is
1534 pragma Assert (Self_ID.Deferral_Level > 0);
1535 pragma Assert (Self_ID = Self);
1536 pragma Assert (Self_ID.Master_Within = Self_ID.Master_of_Task + 1
1538 Self_ID.Master_Within = Self_ID.Master_of_Task + 2);
1539 pragma Assert (Self_ID.Common.Wait_Count = 0);
1540 pragma Assert (Self_ID.Open_Accepts = null);
1541 pragma Assert (Self_ID.ATC_Nesting_Level = 1);
1543 pragma Debug (Debug.Trace (Self_ID, "V_Complete_Task", 'C'));
1549 Write_Lock (Self_ID);
1550 Self_ID.Callable := False;
1552 -- In theory, Self should have no pending entry calls left on its
1553 -- call-stack. Each async. select statement should clean its own call,
1554 -- and blocking entry calls should defer abort until the calls are
1555 -- cancelled, then clean up.
1557 Utilities.Cancel_Queued_Entry_Calls (Self_ID);
1560 if Self_ID.Common.Activator /= null then
1561 Vulnerable_Complete_Activation (Self_ID);
1568 -- If Self_ID.Master_Within = Self_ID.Master_of_Task + 2
1569 -- we may have dependent tasks for which we need to wait.
1570 -- Otherwise, we can just exit.
1572 if Self_ID.Master_Within = Self_ID.Master_of_Task + 2 then
1573 Vulnerable_Complete_Master (Self_ID);
1575 end Vulnerable_Complete_Task;
1577 --------------------------
1578 -- Vulnerable_Free_Task --
1579 --------------------------
1581 -- Recover all runtime system storage associated with the task T.
1582 -- This should only be called after T has terminated and will no
1583 -- longer be referenced.
1585 -- For tasks created by an allocator that fails, due to an exception,
1586 -- it is called from Expunge_Unactivated_Tasks.
1588 -- For tasks created by elaboration of task object declarations it
1589 -- is called from the finalization code of the Task_Wrapper procedure.
1590 -- It is also called from Unchecked_Deallocation, for objects that
1591 -- are or contain tasks.
1593 procedure Vulnerable_Free_Task (T : Task_ID) is
1596 (Debug.Trace ("Vulnerable_Free_Task", T, 'C'));
1603 Initialization.Finalize_Attributes_Link.all (T);
1610 if T.Common.Task_Image /= null then
1611 Free_Task_Image (T.Common.Task_Image);
1614 System.Task_Primitives.Operations.Finalize_TCB (T);
1615 end Vulnerable_Free_Task;
1618 -- Establish the Adafinal softlink.
1619 -- This is not done inside the central RTS initialization routine
1620 -- to avoid with-ing this package from System.Tasking.Initialization.
1622 SSL.Adafinal := Finalize_Global_Tasks'Access;
1624 -- Establish soft links for subprograms that manipulate master_id's.
1625 -- This cannot be done when the RTS is initialized, because of various
1626 -- elaboration constraints.
1628 SSL.Current_Master := Stages.Current_Master'Access;
1629 SSL.Enter_Master := Stages.Enter_Master'Access;
1630 SSL.Complete_Master := Stages.Complete_Master'Access;
1631 end System.Tasking.Stages;