1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
5 -- SYSTEM.TASKING.PROTECTED_OBJECTS.OPERATIONS --
9 -- Copyright (C) 1998-2009, 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 -- This package contains all extended primitives related to Protected_Objects
35 -- The handling of protected objects with no entries is done in
36 -- System.Tasking.Protected_Objects, the simple routines for protected
37 -- objects with entries in System.Tasking.Protected_Objects.Entries.
39 -- The split between Entries and Operations is needed to break circular
40 -- dependencies inside the run time.
42 -- This package contains all primitives related to Protected_Objects.
43 -- Note: the compiler generates direct calls to this interface, via Rtsfind.
45 with System.Task_Primitives.Operations;
46 with System.Tasking.Entry_Calls;
47 with System.Tasking.Queuing;
48 with System.Tasking.Rendezvous;
49 with System.Tasking.Utilities;
50 with System.Tasking.Debug;
51 with System.Parameters;
52 with System.Traces.Tasking;
53 with System.Restrictions;
55 with System.Tasking.Initialization;
56 pragma Elaborate_All (System.Tasking.Initialization);
57 -- Insures that tasking is initialized if any protected objects are created
59 package body System.Tasking.Protected_Objects.Operations is
61 package STPO renames System.Task_Primitives.Operations;
68 use System.Restrictions;
69 use System.Restrictions.Rident;
71 use System.Traces.Tasking;
73 -----------------------
74 -- Local Subprograms --
75 -----------------------
77 procedure Update_For_Queue_To_PO
78 (Entry_Call : Entry_Call_Link;
79 With_Abort : Boolean);
80 pragma Inline (Update_For_Queue_To_PO);
81 -- Update the state of an existing entry call to reflect the fact that it
82 -- is being enqueued, based on whether the current queuing action is with
83 -- or without abort. Call this only while holding the PO's lock. It returns
84 -- with the PO's lock still held.
86 procedure Requeue_Call
88 Object : Protection_Entries_Access;
89 Entry_Call : Entry_Call_Link);
90 -- Handle requeue of Entry_Call.
91 -- In particular, queue the call if needed, or service it immediately
94 ---------------------------------
95 -- Cancel_Protected_Entry_Call --
96 ---------------------------------
98 -- Compiler interface only (do not call from within the RTS)
100 -- This should have analogous effect to Cancel_Task_Entry_Call, setting
101 -- the value of Block.Cancelled instead of returning the parameter value
104 -- The effect should be idempotent, since the call may already have been
118 -- X : protected_entry_index := 1;
119 -- B80b : communication_block;
120 -- communication_blockIP (B80b);
126 -- procedure _clean is
128 -- if enqueued (B80b) then
129 -- cancel_protected_entry_call (B80b);
135 -- protected_entry_call (rTV!(r)._object'unchecked_access, X,
136 -- null_address, asynchronous_call, B80b, objectF => 0);
137 -- if enqueued (B80b) then
145 -- when _abort_signal =>
146 -- abort_undefer.all;
150 -- if not cancelled (B80b) then
155 -- If the entry call completes after we get into the abortable part,
156 -- Abort_Signal should be raised and ATC will take us to the at-end
157 -- handler, which will call _clean.
159 -- If the entry call returns with the call already completed, we can skip
160 -- this, and use the "if enqueued()" to go past the at-end handler, but we
161 -- will still call _clean.
163 -- If the abortable part completes before the entry call is Done, it will
166 -- If the entry call or the abortable part raises an exception,
167 -- we will still call _clean, but the value of Cancelled should not matter.
169 -- Whoever calls _clean first gets to decide whether the call
170 -- has been "cancelled".
172 -- Enqueued should be true if there is any chance that the call is still on
173 -- a queue. It seems to be safe to make it True if the call was Onqueue at
174 -- some point before return from Protected_Entry_Call.
176 -- Cancelled should be true iff the abortable part completed
177 -- and succeeded in cancelling the entry call before it completed.
180 -- The need for Enqueued is less obvious. The "if enqueued ()" tests are
181 -- not necessary, since Cancel_Protected_Entry_Call/Protected_Entry_Call
182 -- must do the same test internally, with locking. The one that makes
183 -- cancellation conditional may be a useful heuristic since at least 1/2
184 -- the time the call should be off-queue by that point. The other one seems
185 -- totally useless, since Protected_Entry_Call must do the same check and
186 -- then possibly wait for the call to be abortable, internally.
188 -- We can check Call.State here without locking the caller's mutex,
189 -- since the call must be over after returning from Wait_For_Completion.
190 -- No other task can access the call record at this point.
192 procedure Cancel_Protected_Entry_Call
193 (Block : in out Communication_Block) is
195 Entry_Calls.Try_To_Cancel_Entry_Call (Block.Cancelled);
196 end Cancel_Protected_Entry_Call;
202 function Cancelled (Block : Communication_Block) return Boolean is
204 return Block.Cancelled;
207 -------------------------
208 -- Complete_Entry_Body --
209 -------------------------
211 procedure Complete_Entry_Body (Object : Protection_Entries_Access) is
213 Exceptional_Complete_Entry_Body (Object, Ada.Exceptions.Null_Id);
214 end Complete_Entry_Body;
220 function Enqueued (Block : Communication_Block) return Boolean is
222 return Block.Enqueued;
225 -------------------------------------
226 -- Exceptional_Complete_Entry_Body --
227 -------------------------------------
229 procedure Exceptional_Complete_Entry_Body
230 (Object : Protection_Entries_Access;
231 Ex : Ada.Exceptions.Exception_Id)
233 procedure Transfer_Occurrence
234 (Target : Ada.Exceptions.Exception_Occurrence_Access;
235 Source : Ada.Exceptions.Exception_Occurrence);
236 pragma Import (C, Transfer_Occurrence, "__gnat_transfer_occurrence");
238 Entry_Call : constant Entry_Call_Link := Object.Call_In_Progress;
243 (Debug.Trace (STPO.Self, "Exceptional_Complete_Entry_Body", 'P'));
245 -- We must have abort deferred, since we are inside a protected
248 if Entry_Call /= null then
250 -- The call was not requeued
252 Entry_Call.Exception_To_Raise := Ex;
254 if Ex /= Ada.Exceptions.Null_Id then
256 -- An exception was raised and abort was deferred, so adjust
257 -- before propagating, otherwise the task will stay with deferral
258 -- enabled for its remaining life.
260 Self_Id := STPO.Self;
261 Initialization.Undefer_Abort_Nestable (Self_Id);
263 (Entry_Call.Self.Common.Compiler_Data.Current_Excep'Access,
264 Self_Id.Common.Compiler_Data.Current_Excep);
267 -- Wakeup_Entry_Caller will be called from PO_Do_Or_Queue or
268 -- PO_Service_Entries on return.
272 if Runtime_Traces then
273 Send_Trace_Info (PO_Done, Entry_Call.Self);
275 end Exceptional_Complete_Entry_Body;
281 procedure PO_Do_Or_Queue
283 Object : Protection_Entries_Access;
284 Entry_Call : Entry_Call_Link)
286 E : constant Protected_Entry_Index :=
287 Protected_Entry_Index (Entry_Call.E);
288 Barrier_Value : Boolean;
291 -- When the Action procedure for an entry body returns, it is either
292 -- completed (having called [Exceptional_]Complete_Entry_Body) or it
293 -- is queued, having executed a requeue statement.
296 Object.Entry_Bodies (
297 Object.Find_Body_Index (Object.Compiler_Info, E)).
298 Barrier (Object.Compiler_Info, E);
300 if Barrier_Value then
302 -- Not abortable while service is in progress
304 if Entry_Call.State = Now_Abortable then
305 Entry_Call.State := Was_Abortable;
308 Object.Call_In_Progress := Entry_Call;
311 (Debug.Trace (Self_ID, "PODOQ: start entry body", 'P'));
312 Object.Entry_Bodies (
313 Object.Find_Body_Index (Object.Compiler_Info, E)).Action (
314 Object.Compiler_Info, Entry_Call.Uninterpreted_Data, E);
316 if Object.Call_In_Progress /= null then
318 -- Body of current entry served call to completion
320 Object.Call_In_Progress := null;
326 STPO.Write_Lock (Entry_Call.Self);
327 Initialization.Wakeup_Entry_Caller (Self_ID, Entry_Call, Done);
328 STPO.Unlock (Entry_Call.Self);
335 Requeue_Call (Self_ID, Object, Entry_Call);
338 elsif Entry_Call.Mode /= Conditional_Call
339 or else not Entry_Call.With_Abort
342 if Run_Time_Restrictions.Set (Max_Entry_Queue_Length)
344 Run_Time_Restrictions.Value (Max_Entry_Queue_Length) <=
345 Queuing.Count_Waiting (Object.Entry_Queues (E))
347 -- This violates the Max_Entry_Queue_Length restriction,
348 -- raise Program_Error.
350 Entry_Call.Exception_To_Raise := Program_Error'Identity;
356 STPO.Write_Lock (Entry_Call.Self);
357 Initialization.Wakeup_Entry_Caller (Self_ID, Entry_Call, Done);
358 STPO.Unlock (Entry_Call.Self);
364 Queuing.Enqueue (Object.Entry_Queues (E), Entry_Call);
365 Update_For_Queue_To_PO (Entry_Call, Entry_Call.With_Abort);
368 -- Conditional_Call and With_Abort
374 STPO.Write_Lock (Entry_Call.Self);
375 pragma Assert (Entry_Call.State >= Was_Abortable);
376 Initialization.Wakeup_Entry_Caller (Self_ID, Entry_Call, Cancelled);
377 STPO.Unlock (Entry_Call.Self);
386 Queuing.Broadcast_Program_Error (Self_ID, Object, Entry_Call);
389 ------------------------
390 -- PO_Service_Entries --
391 ------------------------
393 procedure PO_Service_Entries
395 Object : Entries.Protection_Entries_Access;
396 Unlock_Object : Boolean := True)
398 E : Protected_Entry_Index;
400 Entry_Call : Entry_Call_Link;
404 Queuing.Select_Protected_Entry_Call (Self_ID, Object, Entry_Call);
406 exit when Entry_Call = null;
408 E := Protected_Entry_Index (Entry_Call.E);
410 -- Not abortable while service is in progress
412 if Entry_Call.State = Now_Abortable then
413 Entry_Call.State := Was_Abortable;
416 Object.Call_In_Progress := Entry_Call;
419 if Runtime_Traces then
420 Send_Trace_Info (PO_Run, Self_ID,
421 Entry_Call.Self, Entry_Index (E));
425 (Debug.Trace (Self_ID, "POSE: start entry body", 'P'));
428 (Object.Find_Body_Index (Object.Compiler_Info, E)).Action
429 (Object.Compiler_Info, Entry_Call.Uninterpreted_Data, E);
433 Queuing.Broadcast_Program_Error
434 (Self_ID, Object, Entry_Call);
437 if Object.Call_In_Progress = null then
438 Requeue_Call (Self_ID, Object, Entry_Call);
439 exit when Entry_Call.State = Cancelled;
442 Object.Call_In_Progress := null;
443 Caller := Entry_Call.Self;
449 STPO.Write_Lock (Caller);
450 Initialization.Wakeup_Entry_Caller (Self_ID, Entry_Call, Done);
451 STPO.Unlock (Caller);
459 if Unlock_Object then
460 Unlock_Entries (Object);
462 end PO_Service_Entries;
464 ---------------------
465 -- Protected_Count --
466 ---------------------
468 function Protected_Count
469 (Object : Protection_Entries'Class;
470 E : Protected_Entry_Index) return Natural
473 return Queuing.Count_Waiting (Object.Entry_Queues (E));
476 --------------------------
477 -- Protected_Entry_Call --
478 --------------------------
480 -- Compiler interface only (do not call from within the RTS)
489 -- X : protected_entry_index := 1;
490 -- B85b : communication_block;
491 -- communication_blockIP (B85b);
494 -- protected_entry_call (rTV!(r)._object'unchecked_access, X,
495 -- null_address, conditional_call, B85b, objectF => 0);
497 -- if cancelled (B85b) then
504 -- See also Cancel_Protected_Entry_Call for code expansion of asynchronous
507 -- The initial part of this procedure does not need to lock the calling
508 -- task's ATCB, up to the point where the call record first may be queued
509 -- (PO_Do_Or_Queue), since before that no other task will have access to
512 -- If this is a call made inside of an abort deferred region, the call
513 -- should be never abortable.
515 -- If the call was not queued abortably, we need to wait until it is before
516 -- proceeding with the abortable part.
518 -- There are some heuristics here, just to save time for frequently
519 -- occurring cases. For example, we check Initially_Abortable to try to
520 -- avoid calling the procedure Wait_Until_Abortable, since the normal case
521 -- for async. entry calls is to be queued abortably.
523 -- Another heuristic uses the Block.Enqueued to try to avoid calling
524 -- Cancel_Protected_Entry_Call if the call can be served immediately.
526 procedure Protected_Entry_Call
527 (Object : Protection_Entries_Access;
528 E : Protected_Entry_Index;
529 Uninterpreted_Data : System.Address;
531 Block : out Communication_Block)
533 Self_ID : constant Task_Id := STPO.Self;
534 Entry_Call : Entry_Call_Link;
535 Initially_Abortable : Boolean;
536 Ceiling_Violation : Boolean;
540 (Debug.Trace (Self_ID, "Protected_Entry_Call", 'P'));
542 if Runtime_Traces then
543 Send_Trace_Info (PO_Call, Entry_Index (E));
546 if Self_ID.ATC_Nesting_Level = ATC_Level'Last then
547 raise Storage_Error with "not enough ATC nesting levels";
550 -- If pragma Detect_Blocking is active then Program_Error must be
551 -- raised if this potentially blocking operation is called from a
555 and then Self_ID.Common.Protected_Action_Nesting > 0
557 raise Program_Error with "potentially blocking operation";
560 -- Self_ID.Deferral_Level should be 0, except when called from Finalize,
561 -- where abort is already deferred.
563 Initialization.Defer_Abort_Nestable (Self_ID);
564 Lock_Entries (Object, Ceiling_Violation);
566 if Ceiling_Violation then
568 -- Failed ceiling check
570 Initialization.Undefer_Abort_Nestable (Self_ID);
574 Block.Self := Self_ID;
575 Self_ID.ATC_Nesting_Level := Self_ID.ATC_Nesting_Level + 1;
577 (Debug.Trace (Self_ID, "PEC: entered ATC level: " &
578 ATC_Level'Image (Self_ID.ATC_Nesting_Level), 'A'));
580 Self_ID.Entry_Calls (Self_ID.ATC_Nesting_Level)'Access;
581 Entry_Call.Next := null;
582 Entry_Call.Mode := Mode;
583 Entry_Call.Cancellation_Attempted := False;
586 (if Self_ID.Deferral_Level > 1
587 then Never_Abortable else Now_Abortable);
589 Entry_Call.E := Entry_Index (E);
590 Entry_Call.Prio := STPO.Get_Priority (Self_ID);
591 Entry_Call.Uninterpreted_Data := Uninterpreted_Data;
592 Entry_Call.Called_PO := To_Address (Object);
593 Entry_Call.Called_Task := null;
594 Entry_Call.Exception_To_Raise := Ada.Exceptions.Null_Id;
595 Entry_Call.With_Abort := True;
597 PO_Do_Or_Queue (Self_ID, Object, Entry_Call);
598 Initially_Abortable := Entry_Call.State = Now_Abortable;
599 PO_Service_Entries (Self_ID, Object);
601 -- Try to prevent waiting later (in Try_To_Cancel_Protected_Entry_Call)
602 -- for completed or cancelled calls. (This is a heuristic, only.)
604 if Entry_Call.State >= Done then
606 -- Once State >= Done it will not change any more
612 STPO.Write_Lock (Self_ID);
613 Utilities.Exit_One_ATC_Level (Self_ID);
614 STPO.Unlock (Self_ID);
620 Block.Enqueued := False;
621 Block.Cancelled := Entry_Call.State = Cancelled;
622 Initialization.Undefer_Abort_Nestable (Self_ID);
623 Entry_Calls.Check_Exception (Self_ID, Entry_Call);
627 -- In this case we cannot conclude anything, since State can change
633 -- Now for the general case
635 if Mode = Asynchronous_Call then
637 -- Try to avoid an expensive call
639 if not Initially_Abortable then
642 Entry_Calls.Wait_Until_Abortable (Self_ID, Entry_Call);
645 Entry_Calls.Wait_Until_Abortable (Self_ID, Entry_Call);
649 elsif Mode < Asynchronous_Call then
651 -- Simple_Call or Conditional_Call
655 Entry_Calls.Wait_For_Completion (Entry_Call);
659 STPO.Write_Lock (Self_ID);
660 Entry_Calls.Wait_For_Completion (Entry_Call);
661 STPO.Unlock (Self_ID);
664 Block.Cancelled := Entry_Call.State = Cancelled;
667 pragma Assert (False);
671 Initialization.Undefer_Abort_Nestable (Self_ID);
672 Entry_Calls.Check_Exception (Self_ID, Entry_Call);
673 end Protected_Entry_Call;
679 procedure Requeue_Call
681 Object : Protection_Entries_Access;
682 Entry_Call : Entry_Call_Link)
684 New_Object : Protection_Entries_Access;
685 Ceiling_Violation : Boolean;
687 E : Protected_Entry_Index;
690 New_Object := To_Protection (Entry_Call.Called_PO);
692 if New_Object = null then
694 -- Call is to be requeued to a task entry
700 Result := Rendezvous.Task_Do_Or_Queue (Self_Id, Entry_Call);
703 Queuing.Broadcast_Program_Error
704 (Self_Id, Object, Entry_Call, RTS_Locked => True);
712 -- Call should be requeued to a PO
714 if Object /= New_Object then
716 -- Requeue is to different PO
718 Lock_Entries (New_Object, Ceiling_Violation);
720 if Ceiling_Violation then
721 Object.Call_In_Progress := null;
722 Queuing.Broadcast_Program_Error (Self_Id, Object, Entry_Call);
725 PO_Do_Or_Queue (Self_Id, New_Object, Entry_Call);
726 PO_Service_Entries (Self_Id, New_Object);
730 -- Requeue is to same protected object
732 -- ??? Try to compensate apparent failure of the scheduler on some
733 -- OS (e.g VxWorks) to give higher priority tasks a chance to run
738 if Entry_Call.With_Abort
739 and then Entry_Call.Cancellation_Attempted
741 -- If this is a requeue with abort and someone tried to cancel
742 -- this call, cancel it at this point.
744 Entry_Call.State := Cancelled;
748 if not Entry_Call.With_Abort
749 or else Entry_Call.Mode /= Conditional_Call
751 E := Protected_Entry_Index (Entry_Call.E);
753 if Run_Time_Restrictions.Set (Max_Entry_Queue_Length)
755 Run_Time_Restrictions.Value (Max_Entry_Queue_Length) <=
756 Queuing.Count_Waiting (Object.Entry_Queues (E))
758 -- This violates the Max_Entry_Queue_Length restriction,
759 -- raise Program_Error.
761 Entry_Call.Exception_To_Raise := Program_Error'Identity;
767 STPO.Write_Lock (Entry_Call.Self);
768 Initialization.Wakeup_Entry_Caller
769 (Self_Id, Entry_Call, Done);
770 STPO.Unlock (Entry_Call.Self);
778 (New_Object.Entry_Queues (E), Entry_Call);
779 Update_For_Queue_To_PO (Entry_Call, Entry_Call.With_Abort);
783 PO_Do_Or_Queue (Self_Id, New_Object, Entry_Call);
789 ----------------------------
790 -- Protected_Entry_Caller --
791 ----------------------------
793 function Protected_Entry_Caller
794 (Object : Protection_Entries'Class) return Task_Id is
796 return Object.Call_In_Progress.Self;
797 end Protected_Entry_Caller;
799 -----------------------------
800 -- Requeue_Protected_Entry --
801 -----------------------------
803 -- Compiler interface only (do not call from within the RTS)
812 -- procedure rPT__E10b (O : address; P : address; E :
813 -- protected_entry_index) is
814 -- type rTVP is access rTV;
816 -- _object : rTVP := rTVP!(O);
819 -- rR : protection renames _object._object;
820 -- vP : integer renames _object.v;
821 -- bP : boolean renames _object.b;
825 -- requeue_protected_entry (rR'unchecked_access, rR'
826 -- unchecked_access, 2, false, objectF => 0, new_objectF =>
830 -- complete_entry_body (_object._object'unchecked_access, objectF =>
835 -- abort_undefer.all;
836 -- exceptional_complete_entry_body (_object._object'
837 -- unchecked_access, current_exception, objectF => 0);
841 procedure Requeue_Protected_Entry
842 (Object : Protection_Entries_Access;
843 New_Object : Protection_Entries_Access;
844 E : Protected_Entry_Index;
845 With_Abort : Boolean)
847 Entry_Call : constant Entry_Call_Link := Object.Call_In_Progress;
851 (Debug.Trace (STPO.Self, "Requeue_Protected_Entry", 'P'));
852 pragma Assert (STPO.Self.Deferral_Level > 0);
854 Entry_Call.E := Entry_Index (E);
855 Entry_Call.Called_PO := To_Address (New_Object);
856 Entry_Call.Called_Task := null;
857 Entry_Call.With_Abort := With_Abort;
858 Object.Call_In_Progress := null;
859 end Requeue_Protected_Entry;
861 -------------------------------------
862 -- Requeue_Task_To_Protected_Entry --
863 -------------------------------------
865 -- Compiler interface only (do not call from within the RTS)
876 -- accept_call (1, A79b);
878 -- requeue_task_to_protected_entry (rTV!(r)._object'
879 -- unchecked_access, 2, false, new_objectF => 0);
882 -- complete_rendezvous;
885 -- when all others =>
886 -- exceptional_complete_rendezvous (get_gnat_exception);
889 procedure Requeue_Task_To_Protected_Entry
890 (New_Object : Protection_Entries_Access;
891 E : Protected_Entry_Index;
892 With_Abort : Boolean)
894 Self_ID : constant Task_Id := STPO.Self;
895 Entry_Call : constant Entry_Call_Link := Self_ID.Common.Call;
898 Initialization.Defer_Abort (Self_ID);
900 -- We do not need to lock Self_ID here since the call is not abortable
901 -- at this point, and therefore, the caller cannot cancel the call.
903 Entry_Call.Needs_Requeue := True;
904 Entry_Call.With_Abort := With_Abort;
905 Entry_Call.Called_PO := To_Address (New_Object);
906 Entry_Call.Called_Task := null;
907 Entry_Call.E := Entry_Index (E);
908 Initialization.Undefer_Abort (Self_ID);
909 end Requeue_Task_To_Protected_Entry;
911 ---------------------
912 -- Service_Entries --
913 ---------------------
915 procedure Service_Entries (Object : Protection_Entries_Access) is
916 Self_ID : constant Task_Id := STPO.Self;
918 PO_Service_Entries (Self_ID, Object);
921 --------------------------------
922 -- Timed_Protected_Entry_Call --
923 --------------------------------
925 -- Compiler interface only (do not call from within the RTS)
927 procedure Timed_Protected_Entry_Call
928 (Object : Protection_Entries_Access;
929 E : Protected_Entry_Index;
930 Uninterpreted_Data : System.Address;
933 Entry_Call_Successful : out Boolean)
935 Self_Id : constant Task_Id := STPO.Self;
936 Entry_Call : Entry_Call_Link;
937 Ceiling_Violation : Boolean;
940 pragma Unreferenced (Yielded);
943 if Self_Id.ATC_Nesting_Level = ATC_Level'Last then
944 raise Storage_Error with "not enough ATC nesting levels";
947 -- If pragma Detect_Blocking is active then Program_Error must be
948 -- raised if this potentially blocking operation is called from a
952 and then Self_Id.Common.Protected_Action_Nesting > 0
954 raise Program_Error with "potentially blocking operation";
957 if Runtime_Traces then
958 Send_Trace_Info (POT_Call, Entry_Index (E), Timeout);
961 Initialization.Defer_Abort (Self_Id);
962 Lock_Entries (Object, Ceiling_Violation);
964 if Ceiling_Violation then
965 Initialization.Undefer_Abort (Self_Id);
969 Self_Id.ATC_Nesting_Level := Self_Id.ATC_Nesting_Level + 1;
971 (Debug.Trace (Self_Id, "TPEC: exited to ATC level: " &
972 ATC_Level'Image (Self_Id.ATC_Nesting_Level), 'A'));
973 Entry_Call := Self_Id.Entry_Calls (Self_Id.ATC_Nesting_Level)'Access;
974 Entry_Call.Next := null;
975 Entry_Call.Mode := Timed_Call;
976 Entry_Call.Cancellation_Attempted := False;
979 (if Self_Id.Deferral_Level > 1
983 Entry_Call.E := Entry_Index (E);
984 Entry_Call.Prio := STPO.Get_Priority (Self_Id);
985 Entry_Call.Uninterpreted_Data := Uninterpreted_Data;
986 Entry_Call.Called_PO := To_Address (Object);
987 Entry_Call.Called_Task := null;
988 Entry_Call.Exception_To_Raise := Ada.Exceptions.Null_Id;
989 Entry_Call.With_Abort := True;
991 PO_Do_Or_Queue (Self_Id, Object, Entry_Call);
992 PO_Service_Entries (Self_Id, Object);
997 STPO.Write_Lock (Self_Id);
1000 -- Try to avoid waiting for completed or cancelled calls
1002 if Entry_Call.State >= Done then
1003 Utilities.Exit_One_ATC_Level (Self_Id);
1008 STPO.Unlock (Self_Id);
1011 Entry_Call_Successful := Entry_Call.State = Done;
1012 Initialization.Undefer_Abort (Self_Id);
1013 Entry_Calls.Check_Exception (Self_Id, Entry_Call);
1017 Entry_Calls.Wait_For_Completion_With_Timeout
1018 (Entry_Call, Timeout, Mode, Yielded);
1023 STPO.Unlock (Self_Id);
1026 -- ??? Do we need to yield in case Yielded is False
1028 Initialization.Undefer_Abort (Self_Id);
1029 Entry_Call_Successful := Entry_Call.State = Done;
1030 Entry_Calls.Check_Exception (Self_Id, Entry_Call);
1031 end Timed_Protected_Entry_Call;
1033 ----------------------------
1034 -- Update_For_Queue_To_PO --
1035 ----------------------------
1037 -- Update the state of an existing entry call, based on
1038 -- whether the current queuing action is with or without abort.
1039 -- Call this only while holding the server's lock.
1040 -- It returns with the server's lock released.
1042 New_State : constant array (Boolean, Entry_Call_State)
1043 of Entry_Call_State :=
1045 (Never_Abortable => Never_Abortable,
1046 Not_Yet_Abortable => Now_Abortable,
1047 Was_Abortable => Now_Abortable,
1048 Now_Abortable => Now_Abortable,
1050 Cancelled => Cancelled),
1052 (Never_Abortable => Never_Abortable,
1053 Not_Yet_Abortable => Not_Yet_Abortable,
1054 Was_Abortable => Was_Abortable,
1055 Now_Abortable => Now_Abortable,
1057 Cancelled => Cancelled)
1060 procedure Update_For_Queue_To_PO
1061 (Entry_Call : Entry_Call_Link;
1062 With_Abort : Boolean)
1064 Old : constant Entry_Call_State := Entry_Call.State;
1067 pragma Assert (Old < Done);
1069 Entry_Call.State := New_State (With_Abort, Entry_Call.State);
1071 if Entry_Call.Mode = Asynchronous_Call then
1072 if Old < Was_Abortable and then
1073 Entry_Call.State = Now_Abortable
1079 STPO.Write_Lock (Entry_Call.Self);
1081 if Entry_Call.Self.Common.State = Async_Select_Sleep then
1082 STPO.Wakeup (Entry_Call.Self, Async_Select_Sleep);
1085 STPO.Unlock (Entry_Call.Self);
1093 elsif Entry_Call.Mode = Conditional_Call then
1094 pragma Assert (Entry_Call.State < Was_Abortable);
1097 end Update_For_Queue_To_PO;
1099 end System.Tasking.Protected_Objects.Operations;