1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
5 -- S Y S T E M . T A S K I N G . R E S T R I C T E D . S T A G E S --
9 -- Copyright (C) 1999-2006, Free Software Foundation, Inc. --
11 -- GNARL is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 2, or (at your option) any later ver- --
14 -- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNARL; see file COPYING. If not, write --
19 -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, USA. --
22 -- As a special exception, if other files instantiate generics from this --
23 -- unit, or you link this unit with other files to produce an executable, --
24 -- this unit does not by itself cause the resulting executable to be --
25 -- covered by the GNU General Public License. This exception does not --
26 -- however invalidate any other reasons why the executable file might be --
27 -- covered by the GNU Public License. --
29 -- GNARL was developed by the GNARL team at Florida State University. --
30 -- Extensive contributions were provided by Ada Core Technologies, Inc. --
32 ------------------------------------------------------------------------------
34 pragma Style_Checks (All_Checks);
35 -- Turn off subprogram alpha order check, since we group soft link
36 -- bodies and also separate off subprograms for restricted GNARLI.
38 -- This is a simplified version of the System.Tasking.Stages package,
39 -- intended to be used in a restricted run time.
41 -- This package represents the high level tasking interface used by the
42 -- compiler to expand Ada 95 tasking constructs into simpler run time calls.
45 -- Turn off polling, we do not want ATC polling to take place during
46 -- tasking operations. It causes infinite loops and other problems.
49 -- used for Exception_Occurrence
51 with System.Task_Primitives.Operations;
52 -- used for Enter_Task
58 with System.Soft_Links;
59 -- used for the non-tasking routines (*_NT) that refer to global data.
60 -- They are needed here before the tasking run time has been elaborated.
61 -- used for Create_TSD
62 -- This package also provides initialization routines for task specific data.
63 -- The GNARL must call these to be sure that all non-tasking
64 -- Ada constructs will work.
66 with System.Soft_Links.Tasking;
67 -- Used for Init_Tasking_Soft_Links
69 with System.Secondary_Stack;
72 with System.Storage_Elements;
73 -- used for Storage_Array;
75 package body System.Tasking.Restricted.Stages is
77 package STPO renames System.Task_Primitives.Operations;
78 package SSL renames System.Soft_Links;
79 package SSE renames System.Storage_Elements;
80 package SST renames System.Secondary_Stack;
85 use Task_Primitives.Operations;
88 Global_Task_Lock : aliased System.Task_Primitives.RTS_Lock;
89 -- This is a global lock; it is used to execute in mutual exclusion
90 -- from all other tasks. It is only used by Task_Lock and Task_Unlock.
92 -----------------------------------------------------------------
93 -- Tasking versions of services needed by non-tasking programs --
94 -----------------------------------------------------------------
97 -- Locks out other tasks. Preceding a section of code by Task_Lock and
98 -- following it by Task_Unlock creates a critical region. This is used
99 -- for ensuring that a region of non-tasking code (such as code used to
100 -- allocate memory) is tasking safe. Note that it is valid for calls to
101 -- Task_Lock/Task_Unlock to be nested, and this must work properly, i.e.
102 -- only the corresponding outer level Task_Unlock will actually unlock.
104 procedure Task_Unlock;
105 -- Releases lock previously set by call to Task_Lock. In the nested case,
106 -- all nested locks must be released before other tasks competing for the
107 -- tasking lock are released.
109 -----------------------
110 -- Local Subprograms --
111 -----------------------
113 procedure Task_Wrapper (Self_ID : Task_Id);
114 -- This is the procedure that is called by the GNULL from the
115 -- new context when a task is created. It waits for activation
116 -- and then calls the task body procedure. When the task body
117 -- procedure completes, it terminates the task.
119 procedure Terminate_Task (Self_ID : Task_Id);
120 -- Terminate the calling task.
121 -- This should only be called by the Task_Wrapper procedure.
124 -- This procedure performs the initialization of the GNARL.
125 -- It consists of initializing the environment task, global locks, and
126 -- installing tasking versions of certain operations used by the compiler.
127 -- Init_RTS is called during elaboration.
133 procedure Task_Lock is
134 Self_ID : constant Task_Id := STPO.Self;
137 Self_ID.Common.Global_Task_Lock_Nesting :=
138 Self_ID.Common.Global_Task_Lock_Nesting + 1;
140 if Self_ID.Common.Global_Task_Lock_Nesting = 1 then
141 STPO.Write_Lock (Global_Task_Lock'Access, Global_Lock => True);
149 procedure Task_Unlock is
150 Self_ID : constant Task_Id := STPO.Self;
153 pragma Assert (Self_ID.Common.Global_Task_Lock_Nesting > 0);
154 Self_ID.Common.Global_Task_Lock_Nesting :=
155 Self_ID.Common.Global_Task_Lock_Nesting - 1;
157 if Self_ID.Common.Global_Task_Lock_Nesting = 0 then
158 STPO.Unlock (Global_Task_Lock'Access, Global_Lock => True);
166 -- The task wrapper is a procedure that is called first for each task
167 -- task body, and which in turn calls the compiler-generated task body
168 -- procedure. The wrapper's main job is to do initialization for the task.
170 -- The variable ID in the task wrapper is used to implement the Self
171 -- function on targets where there is a fast way to find the stack base
172 -- of the current thread, since it should be at a fixed offset from the
175 procedure Task_Wrapper (Self_ID : Task_Id) is
176 ID : Task_Id := Self_ID;
177 pragma Volatile (ID);
178 pragma Warnings (Off, ID);
179 -- Variable used on some targets to implement a fast self. We turn off
180 -- warnings because a stand alone volatile constant has to be imported,
181 -- so we don't want warnings about ID not being referenced, and volatile
184 -- DO NOT delete ID. As noted, it is needed on some targets.
186 use type System.Parameters.Size_Type;
187 use type SSE.Storage_Offset;
189 Secondary_Stack : aliased SSE.Storage_Array
190 (1 .. Self_ID.Common.Compiler_Data.Pri_Stack_Info.Size *
191 SSE.Storage_Offset (Parameters.Sec_Stack_Ratio) / 100);
193 pragma Warnings (Off);
194 Secondary_Stack_Address : System.Address := Secondary_Stack'Address;
195 pragma Warnings (On);
196 -- Address of secondary stack. In the fixed secondary stack case, this
197 -- value is not modified, causing a warning, hence the bracketing with
198 -- Warnings (Off/On).
200 Cause : Cause_Of_Termination := Normal;
201 -- Indicates the reason why this task terminates. Normal corresponds to
202 -- a task terminating due to completing the last statement of its body.
203 -- If the task terminates because of an exception raised by the
204 -- execution of its task body, then Cause is set to Unhandled_Exception.
205 -- Aborts are not allowed in the restriced profile to which this file
208 EO : Exception_Occurrence;
209 -- If the task terminates because of an exception raised by the
210 -- execution of its task body, then EO will contain the associated
211 -- exception occurrence. Otherwise, it will contain Null_Occurrence.
214 if not Parameters.Sec_Stack_Dynamic then
215 Self_ID.Common.Compiler_Data.Sec_Stack_Addr :=
216 Secondary_Stack'Address;
217 SST.SS_Init (Secondary_Stack_Address, Integer (Secondary_Stack'Last));
220 -- Initialize low-level TCB components, that
221 -- cannot be initialized by the creator.
223 Enter_Task (Self_ID);
225 -- Call the task body procedure
228 -- We are separating the following portion of the code in order to
229 -- place the exception handlers in a different block. In this way we
230 -- do not call Set_Jmpbuf_Address (which needs Self) before we set
231 -- Self in Enter_Task.
233 -- Note that in the case of Ravenscar HI-E where there are no
234 -- exception handlers, the exception handler is suppressed.
236 -- Call the task body procedure
238 Self_ID.Common.Task_Entry_Point (Self_ID.Common.Task_Arg);
240 -- Normal task termination
243 Save_Occurrence (EO, Ada.Exceptions.Null_Occurrence);
248 -- Task terminating because of an unhandled exception
250 Cause := Unhandled_Exception;
251 Save_Occurrence (EO, E);
254 -- Look for a fall-back handler. It can be either in the task itself
255 -- or in the environment task. Note that this code is always executed
256 -- by a task whose master is the environment task. The task termination
257 -- code for the environment task is executed by
258 -- SSL.Task_Termination_Handler.
260 -- This package is part of the restricted run time which supports
261 -- neither task hierarchies (No_Task_Hierarchy) nor specific task
262 -- termination handlers (No_Specific_Termination_Handlers).
264 -- There is no need for explicit protection against race conditions
265 -- for Self_ID.Common.Fall_Back_Handler because this procedure can
266 -- only be executed by Self, and the Fall_Back_Handler can only be
269 if Self_ID.Common.Fall_Back_Handler /= null then
270 Self_ID.Common.Fall_Back_Handler (Cause, Self_ID, EO);
273 TH : Termination_Handler := null;
280 Write_Lock (Self_ID.Common.Parent);
282 TH := Self_ID.Common.Parent.Common.Fall_Back_Handler;
284 Unlock (Self_ID.Common.Parent);
290 -- Execute the task termination handler if we found it
293 TH.all (Cause, Self_ID, EO);
298 Terminate_Task (Self_ID);
301 -----------------------
302 -- Restricted GNARLI --
303 -----------------------
305 -------------------------------
306 -- Activate_Restricted_Tasks --
307 -------------------------------
309 -- Note that locks of activator and activated task are both locked here.
310 -- This is necessary because C.State and Self.Wait_Count have to be
311 -- synchronized. This is safe from deadlock because the activator is always
312 -- created before the activated task. That satisfies our
313 -- in-order-of-creation ATCB locking policy.
315 procedure Activate_Restricted_Tasks
316 (Chain_Access : Activation_Chain_Access)
318 Self_ID : constant Task_Id := STPO.Self;
320 Activate_Prio : System.Any_Priority;
324 pragma Assert (Self_ID = Environment_Task);
325 pragma Assert (Self_ID.Common.Wait_Count = 0);
331 -- Lock self, to prevent activated tasks from racing ahead before we
332 -- finish activating the chain.
334 Write_Lock (Self_ID);
336 -- Activate all the tasks in the chain. Creation of the thread of
337 -- control was deferred until activation. So create it now.
339 C := Chain_Access.T_ID;
342 if C.Common.State /= Terminated then
343 pragma Assert (C.Common.State = Unactivated);
347 if C.Common.Base_Priority < Get_Priority (Self_ID) then
348 Activate_Prio := Get_Priority (Self_ID);
350 Activate_Prio := C.Common.Base_Priority;
354 (C, Task_Wrapper'Address,
356 (C.Common.Compiler_Data.Pri_Stack_Info.Size),
357 Activate_Prio, Success);
359 Self_ID.Common.Wait_Count := Self_ID.Common.Wait_Count + 1;
362 C.Common.State := Runnable;
370 C := C.Common.Activation_Link;
373 Self_ID.Common.State := Activator_Sleep;
375 -- Wait for the activated tasks to complete activation. It is unsafe to
376 -- abort any of these tasks until the count goes to zero.
379 exit when Self_ID.Common.Wait_Count = 0;
380 Sleep (Self_ID, Activator_Sleep);
383 Self_ID.Common.State := Runnable;
390 -- Remove the tasks from the chain
392 Chain_Access.T_ID := null;
393 end Activate_Restricted_Tasks;
395 ------------------------------------
396 -- Complete_Restricted_Activation --
397 ------------------------------------
399 -- As in several other places, the locks of the activator and activated
400 -- task are both locked here. This follows our deadlock prevention lock
401 -- ordering policy, since the activated task must be created after the
404 procedure Complete_Restricted_Activation is
405 Self_ID : constant Task_Id := STPO.Self;
406 Activator : constant Task_Id := Self_ID.Common.Activator;
413 Write_Lock (Activator);
414 Write_Lock (Self_ID);
416 -- Remove dangling reference to Activator, since a task may outlive its
419 Self_ID.Common.Activator := null;
421 -- Wake up the activator, if it is waiting for a chain of tasks to
422 -- activate, and we are the last in the chain to complete activation
424 if Activator.Common.State = Activator_Sleep then
425 Activator.Common.Wait_Count := Activator.Common.Wait_Count - 1;
427 if Activator.Common.Wait_Count = 0 then
428 Wakeup (Activator, Activator_Sleep);
439 -- After the activation, active priority should be the same as base
440 -- priority. We must unlock the Activator first, though, since it should
441 -- not wait if we have lower priority.
443 if Get_Priority (Self_ID) /= Self_ID.Common.Base_Priority then
444 Set_Priority (Self_ID, Self_ID.Common.Base_Priority);
446 end Complete_Restricted_Activation;
448 ------------------------------
449 -- Complete_Restricted_Task --
450 ------------------------------
452 procedure Complete_Restricted_Task is
454 STPO.Self.Common.State := Terminated;
455 end Complete_Restricted_Task;
457 ----------------------------
458 -- Create_Restricted_Task --
459 ----------------------------
461 procedure Create_Restricted_Task
463 Stack_Address : System.Address;
464 Size : System.Parameters.Size_Type;
465 Task_Info : System.Task_Info.Task_Info_Type;
466 State : Task_Procedure_Access;
467 Discriminants : System.Address;
468 Elaborated : Access_Boolean;
469 Chain : in out Activation_Chain;
471 Created_Task : Task_Id)
473 Self_ID : constant Task_Id := STPO.Self;
474 Base_Priority : System.Any_Priority;
478 -- Stack is not preallocated on this target, so that Stack_Address must
481 pragma Assert (Stack_Address = Null_Address);
483 if Priority = Unspecified_Priority then
484 Base_Priority := Self_ID.Common.Base_Priority;
486 Base_Priority := System.Any_Priority (Priority);
493 Write_Lock (Self_ID);
495 -- With no task hierarchy, the parent of all non-Environment tasks that
496 -- are created must be the Environment task
499 (Self_ID, State, Discriminants, Self_ID, Elaborated, Base_Priority,
500 Task_Info, Size, Created_Task, Success);
502 -- If we do our job right then there should never be any failures, which
503 -- was probably said about the Titanic; so just to be safe, let's retain
516 Created_Task.Entry_Calls (1).Self := Created_Task;
518 Created_Task.Common.Task_Image_Len :=
519 Integer'Min (Created_Task.Common.Task_Image'Length, Task_Image'Length);
520 Created_Task.Common.Task_Image
521 (1 .. Created_Task.Common.Task_Image_Len) := Task_Image;
529 -- Create TSD as early as possible in the creation of a task, since it
530 -- may be used by the operation of Ada code within the task.
532 SSL.Create_TSD (Created_Task.Common.Compiler_Data);
533 Created_Task.Common.Activation_Link := Chain.T_ID;
534 Chain.T_ID := Created_Task;
535 end Create_Restricted_Task;
537 ---------------------------
538 -- Finalize_Global_Tasks --
539 ---------------------------
541 -- This is needed to support the compiler interface; it will only be called
542 -- by the Environment task. Instead, it will cause the Environment to block
543 -- forever, since none of the dependent tasks are expected to terminate
545 procedure Finalize_Global_Tasks is
546 Self_ID : constant Task_Id := STPO.Self;
549 pragma Assert (Self_ID = STPO.Environment_Task);
555 -- Handle normal task termination by the environment task, but only for
556 -- the normal task termination. In the case of Abnormal and
557 -- Unhandled_Exception they must have been handled before, and the task
558 -- termination soft link must have been changed so the task termination
559 -- routine is not executed twice.
561 -- Note that in the "normal" implementation in s-tassta.adb the task
562 -- termination procedure for the environment task should be executed
563 -- after termination of library-level tasks. However, this
564 -- implementation is to be used when the Ravenscar restrictions are in
565 -- effect, and AI-394 says that if there is a fall-back handler set for
566 -- the partition it should be called when the first task (including the
567 -- environment task) attempts to terminate.
569 SSL.Task_Termination_Handler.all (Ada.Exceptions.Null_Occurrence);
571 Write_Lock (Self_ID);
572 Sleep (Self_ID, Master_Completion_Sleep);
579 -- Should never return from Master Completion Sleep
582 end Finalize_Global_Tasks;
584 ---------------------------
585 -- Restricted_Terminated --
586 ---------------------------
588 function Restricted_Terminated (T : Task_Id) return Boolean is
590 return T.Common.State = Terminated;
591 end Restricted_Terminated;
597 procedure Terminate_Task (Self_ID : Task_Id) is
599 Self_ID.Common.State := Terminated;
606 procedure Init_RTS is
610 -- Initialize lock used to implement mutual exclusion between all tasks
612 STPO.Initialize_Lock (Global_Task_Lock'Access, STPO.Global_Task_Level);
614 -- Notify that the tasking run time has been elaborated so that
615 -- the tasking version of the soft links can be used.
617 SSL.Lock_Task := Task_Lock'Access;
618 SSL.Unlock_Task := Task_Unlock'Access;
619 SSL.Adafinal := Finalize_Global_Tasks'Access;
621 -- Initialize the tasking soft links (if not done yet) that are common
622 -- to the full and the restricted run times.
624 SSL.Tasking.Init_Tasking_Soft_Links;
629 end System.Tasking.Restricted.Stages;