1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
5 -- S Y S T E M . T A S K I N G --
9 -- Copyright (C) 1992-2011, 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 provides necessary type definitions for compiler interface
34 -- Note: the compiler generates direct calls to this interface, via Rtsfind.
35 -- Any changes to this interface may require corresponding compiler changes.
38 with Ada
.Unchecked_Conversion
;
40 with System
.Parameters
;
41 with System
.Task_Info
;
42 with System
.Soft_Links
;
43 with System
.Task_Primitives
;
44 with System
.Stack_Usage
;
45 with System
.Multiprocessors
;
47 package System
.Tasking
is
54 -- The following rules must be followed at all times, to prevent
55 -- deadlock and generally ensure correct operation of locking.
57 -- Never lock a lock unless abort is deferred
59 -- Never undefer abort while holding a lock
61 -- Overlapping critical sections must be properly nested, and locks must
62 -- be released in LIFO order. E.g., the following is not allowed:
72 -- Locks with lower (smaller) level number cannot be locked
73 -- while holding a lock with a higher level number. (The level
75 -- 1. System.Tasking.PO_Simple.Protection.L (any PO lock)
76 -- 2. System.Tasking.Initialization.Global_Task_Lock (in body)
77 -- 3. System.Task_Primitives.Operations.Single_RTS_Lock
78 -- 4. System.Tasking.Ada_Task_Control_Block.LL.L (any TCB lock)
80 -- Clearly, there can be no circular chain of hold-and-wait
81 -- relationships involving locks in different ordering levels.
83 -- We used to have Global_Task_Lock before Protection.L but this was
84 -- clearly wrong since there can be calls to "new" inside protected
85 -- operations. The new ordering prevents these failures.
87 -- Sometimes we need to hold two ATCB locks at the same time. To allow us
88 -- to order the locking, each ATCB is given a unique serial number. If one
89 -- needs to hold locks on several ATCBs at once, the locks with lower
90 -- serial numbers must be locked first.
92 -- We don't always need to check the serial numbers, since the serial
93 -- numbers are assigned sequentially, and so:
95 -- . The parent of a task always has a lower serial number.
96 -- . The activator of a task always has a lower serial number.
97 -- . The environment task has a lower serial number than any other task.
98 -- . If the activator of a task is different from the task's parent,
99 -- the parent always has a lower serial number than the activator.
101 ---------------------------------
102 -- Task_Id related definitions --
103 ---------------------------------
105 type Ada_Task_Control_Block
;
107 type Task_Id
is access all Ada_Task_Control_Block
;
108 for Task_Id
'Size use System
.Task_Primitives
.Task_Address_Size
;
110 Null_Task
: constant Task_Id
;
112 type Task_List
is array (Positive range <>) of Task_Id
;
114 function Self
return Task_Id
;
115 pragma Inline
(Self
);
116 -- This is the compiler interface version of this function. Do not call
117 -- from the run-time system.
119 function To_Task_Id
is
120 new Ada
.Unchecked_Conversion
121 (System
.Task_Primitives
.Task_Address
, Task_Id
);
122 function To_Address
is
123 new Ada
.Unchecked_Conversion
124 (Task_Id
, System
.Task_Primitives
.Task_Address
);
126 -----------------------
127 -- Enumeration types --
128 -----------------------
132 -- TCB initialized but not task has not been created.
133 -- It cannot be executing.
136 -- -- ??? Temporarily at end of list for GDB compatibility
137 -- -- Task has been created and is being made Runnable.
140 -- For all states from here down, the task has been activated.
141 -- For all states from here down, except for Terminated, the task
143 -- Activator = null iff it has not yet completed activating.
146 -- Task is not blocked for any reason known to Ada.
147 -- (It may be waiting for a mutex, though.)
148 -- It is conceptually "executing" in normal mode.
151 -- The task is terminated, in the sense of ARM 9.3 (5).
152 -- Any dependents that were waiting on terminate
153 -- alternatives have been awakened and have terminated themselves.
156 -- Task is waiting for created tasks to complete activation
159 -- Task is waiting on an accept or select with terminate
161 -- Acceptor_Delay_Sleep,
162 -- -- ??? Temporarily at end of list for GDB compatibility
163 -- -- Task is waiting on an selective wait statement
166 -- Task is waiting on an entry call
169 -- Task is waiting to start the abortable part of an
170 -- asynchronous select statement.
173 -- Task is waiting on a select statement with only a delay
176 Master_Completion_Sleep
,
177 -- Master completion has two phases.
178 -- In Phase 1 the task is sleeping in Complete_Master
179 -- having completed a master within itself,
180 -- and is waiting for the tasks dependent on that master to become
181 -- terminated or waiting on a terminate Phase.
183 Master_Phase_2_Sleep
,
184 -- In Phase 2 the task is sleeping in Complete_Master
185 -- waiting for tasks on terminate alternatives to finish
188 -- The following are special uses of sleep, for server tasks
189 -- within the run-time system.
191 Interrupt_Server_Idle_Sleep
,
192 Interrupt_Server_Blocked_Interrupt_Sleep
,
197 -- The task has been held by Asynchronous_Task_Control.Hold_Task
199 Interrupt_Server_Blocked_On_Event_Flag
,
200 -- The task has been blocked on a system call waiting for a
201 -- completion event/signal to occur.
204 -- Task has been created and is being made Runnable
207 -- Task is waiting on an selective wait statement
211 (Simple_Call
, Conditional_Call
, Asynchronous_Call
, Timed_Call
);
213 type Select_Modes
is (Simple_Mode
, Else_Mode
, Terminate_Mode
, Delay_Mode
);
215 subtype Delay_Modes
is Integer;
217 -------------------------------
218 -- Entry related definitions --
219 -------------------------------
221 Null_Entry
: constant := 0;
223 Max_Entry
: constant := Integer'Last;
225 Interrupt_Entry
: constant := -2;
227 Cancelled_Entry
: constant := -1;
229 type Entry_Index
is range Interrupt_Entry
.. Max_Entry
;
231 Null_Task_Entry
: constant := Null_Entry
;
233 Max_Task_Entry
: constant := Max_Entry
;
235 type Task_Entry_Index
is new Entry_Index
236 range Null_Task_Entry
.. Max_Task_Entry
;
238 type Entry_Call_Record
;
240 type Entry_Call_Link
is access all Entry_Call_Record
;
242 type Entry_Queue
is record
243 Head
: Entry_Call_Link
;
244 Tail
: Entry_Call_Link
;
247 type Task_Entry_Queue_Array
is
248 array (Task_Entry_Index
range <>) of Entry_Queue
;
250 -- A data structure which contains the string names of entries and entry
253 type String_Access
is access all String;
255 type Entry_Names_Array
is
256 array (Entry_Index
range <>) of String_Access
;
258 type Entry_Names_Array_Access
is access all Entry_Names_Array
;
260 procedure Free_Entry_Names_Array
(Obj
: in out Entry_Names_Array
);
261 -- Deallocate all string names contained in an entry names array
263 ----------------------------------
264 -- Entry_Call_Record definition --
265 ----------------------------------
267 type Entry_Call_State
is
269 -- the call is not abortable, and never can be
272 -- the call is not abortable, but may become so
275 -- the call is not abortable, but once was
278 -- the call is abortable
281 -- the call has been completed
284 -- the call was asynchronous, and was cancelled
286 pragma Ordered
(Entry_Call_State
);
288 -- Never_Abortable is used for calls that are made in a abort deferred
289 -- region (see ARM 9.8(5-11), 9.8 (20)). Such a call is never abortable.
291 -- The Was_ vs. Not_Yet_ distinction is needed to decide whether it is OK
292 -- to advance into the abortable part of an async. select stmt. That is
293 -- allowed iff the mode is Now_ or Was_.
295 -- Done indicates the call has been completed, without cancellation, or no
296 -- call has been made yet at this ATC nesting level, and so aborting the
297 -- call is no longer an issue. Completion of the call does not necessarily
298 -- indicate "success"; the call may be returning an exception if
299 -- Exception_To_Raise is non-null.
301 -- Cancelled indicates the call was cancelled, and so aborting the call is
302 -- no longer an issue.
304 -- The call is on an entry queue unless State >= Done, in which case it may
305 -- or may not be still Onqueue.
307 -- Please do not modify the order of the values, without checking all uses
308 -- of this type. We rely on partial "monotonicity" of
309 -- Entry_Call_Record.State to avoid locking when we access this value for
310 -- certain tests. In particular:
312 -- 1) Once State >= Done, we can rely that the call has been
313 -- completed. If State >= Done, it will not
314 -- change until the task does another entry call at this level.
316 -- 2) Once State >= Was_Abortable, we can rely that the call has
317 -- been queued abortably at least once, and so the check for
318 -- whether it is OK to advance to the abortable part of an
319 -- async. select statement does not need to lock anything.
321 type Restricted_Entry_Call_Record
is record
327 State
: Entry_Call_State
;
328 pragma Atomic
(State
);
329 -- Indicates part of the state of the call.
331 -- Protection: If the call is not on a queue, it should only be
332 -- accessed by Self, and Self does not need any lock to modify this
335 -- Once the call is on a queue, the value should be something other
336 -- than Done unless it is cancelled, and access is controller by the
337 -- "server" of the queue -- i.e., the lock of Checked_To_Protection
338 -- (Call_Target) if the call record is on the queue of a PO, or the
339 -- lock of Called_Target if the call is on the queue of a task. See
340 -- comments on type declaration for more details.
342 Uninterpreted_Data
: System
.Address
;
343 -- Data passed by the compiler
345 Exception_To_Raise
: Ada
.Exceptions
.Exception_Id
;
346 -- The exception to raise once this call has been completed without
349 pragma Suppress_Initialization
(Restricted_Entry_Call_Record
);
351 -------------------------------------------
352 -- Task termination procedure definition --
353 -------------------------------------------
355 -- We need to redefine here these types (already defined in
356 -- Ada.Task_Termination) for avoiding circular dependencies.
358 type Cause_Of_Termination
is (Normal
, Abnormal
, Unhandled_Exception
);
359 -- Possible causes for task termination:
361 -- Normal means that the task terminates due to completing the
362 -- last sentence of its body, or as a result of waiting on a
363 -- terminate alternative.
365 -- Abnormal means that the task terminates because it is being aborted
367 -- handled_Exception means that the task terminates because of exception
368 -- raised by the execution of its task_body.
370 type Termination_Handler
is access protected procedure
371 (Cause
: Cause_Of_Termination
;
373 X
: Ada
.Exceptions
.Exception_Occurrence
);
374 -- Used to represent protected procedures to be executed when task
377 ------------------------------------
378 -- Dispatching domain definitions --
379 ------------------------------------
381 -- We need to redefine here these types (already defined in
382 -- System.Multiprocessor.Dispatching_Domains) for avoiding circular
385 type Dispatching_Domain
is
386 array (System
.Multiprocessors
.CPU
range <>) of Boolean;
387 -- A dispatching domain needs to contain the set of processors belonging
388 -- to it. This is a processor mask where a True indicates that the
389 -- processor belongs to the dispatching domain.
390 -- Do not use the full range of CPU_Range because it would create a very
391 -- long array. This way we can use the exact range of processors available
394 type Dispatching_Domain_Access
is access Dispatching_Domain
;
396 System_Domain
: Dispatching_Domain_Access
;
397 -- All processors belong to default system dispatching domain at start up.
398 -- We use a pointer which creates the actual variable for the reasons
399 -- explained bellow in Dispatching_Domain_Tasks.
401 Dispatching_Domains_Frozen
: Boolean := False;
402 -- True when the main procedure has been called. Hence, no new dispatching
403 -- domains can be created when this flag is True.
405 type Array_Allocated_Tasks
is
406 array (System
.Multiprocessors
.CPU
range <>) of Natural;
407 -- At start-up time, we need to store the number of tasks attached to
408 -- concrete processors within the system domain (we can only create
409 -- dispatching domains with processors belonging to the system domain and
410 -- without tasks allocated).
412 type Array_Allocated_Tasks_Access
is access Array_Allocated_Tasks
;
414 Dispatching_Domain_Tasks
: Array_Allocated_Tasks_Access
;
415 -- We need to store whether there are tasks allocated to concrete
416 -- processors in the default system dispatching domain because we need to
417 -- check it before creating a new dispatching domain. Two comments about
418 -- why we use a pointer here and not in package Dispatching_Domains:
420 -- 1) We use an array created dynamically in procedure Initialize which
421 -- is called at the beginning of the initialization of the run-time
422 -- library. Declaring a static array here in the spec would not work
423 -- across different installations because it would get the value of
424 -- Number_Of_CPUs from the machine where the run-time library is built,
425 -- and not from the machine where the application is executed. That is
426 -- the reason why we create the array (CPU'First .. Number_Of_CPUs) at
427 -- execution time in the procedure body, ensuring that the function
428 -- Number_Of_CPUs is executed at execution time (the same trick as we
429 -- use for System_Domain).
431 -- 2) We have moved this declaration from package Dispatching_Domains
432 -- because when we use a pragma CPU, the affinity is passed through the
433 -- call to Create_Task. Hence, at this point, we may need to update the
434 -- number of tasks associated to the processor, but we do not want to
435 -- force a dependency from this package on Dispatching_Domains.
437 ------------------------------------
438 -- Task related other definitions --
439 ------------------------------------
441 type Activation_Chain
is limited private;
442 -- Linked list of to-be-activated tasks, linked through
443 -- Activation_Link. The order of tasks on the list is irrelevant, because
444 -- the priority rules will ensure that they actually start activating in
447 type Activation_Chain_Access
is access all Activation_Chain
;
449 type Task_Procedure_Access
is access procedure (Arg
: System
.Address
);
451 type Access_Boolean
is access all Boolean;
453 function Detect_Blocking
return Boolean;
454 pragma Inline
(Detect_Blocking
);
455 -- Return whether the Detect_Blocking pragma is enabled
457 function Storage_Size
(T
: Task_Id
) return System
.Parameters
.Size_Type
;
458 -- Retrieve from the TCB of the task the allocated size of its stack,
459 -- either the system default or the size specified by a pragma. This is in
460 -- general a non-static value that can depend on discriminants of the task.
462 type Bit_Array
is array (Integer range <>) of Boolean;
463 pragma Pack
(Bit_Array
);
465 subtype Debug_Event_Array
is Bit_Array
(1 .. 16);
467 Global_Task_Debug_Event_Set
: Boolean := False;
468 -- Set True when running under debugger control and a task debug event
469 -- signal has been requested.
471 ----------------------------------------------
472 -- Ada_Task_Control_Block (ATCB) definition --
473 ----------------------------------------------
475 -- Notes on protection (synchronization) of TRTS data structures
477 -- Any field of the TCB can be written by the activator of a task when the
478 -- task is created, since no other task can access the new task's
479 -- state until creation is complete.
481 -- The protection for each field is described in a comment starting with
484 -- When a lock is used to protect an ATCB field, this lock is simply named
486 -- Some protection is described in terms of tasks related to the
487 -- ATCB being protected. These are:
489 -- Self: The task which is controlled by this ATCB
490 -- Acceptor: A task accepting a call from Self
491 -- Caller: A task calling an entry of Self
492 -- Parent: The task executing the master on which Self depends
493 -- Dependent: A task dependent on Self
494 -- Activator: The task that created Self and initiated its activation
495 -- Created: A task created and activated by Self
497 -- Note: The order of the fields is important to implement efficiently
498 -- tasking support under gdb.
499 -- Currently gdb relies on the order of the State, Parent, Base_Priority,
500 -- Task_Image, Task_Image_Len, Call and LL fields.
502 -------------------------
503 -- Common ATCB section --
504 -------------------------
506 -- Section used by all GNARL implementations (regular and restricted)
508 type Common_ATCB
is record
510 pragma Atomic
(State
);
511 -- Encodes some basic information about the state of a task,
512 -- including whether it has been activated, whether it is sleeping,
513 -- and whether it is terminated.
515 -- Protection: Self.L
518 -- The task on which this task depends.
519 -- See also Master_Level and Master_Within.
521 Base_Priority
: System
.Any_Priority
;
522 -- Base priority, not changed during entry calls, only changed
523 -- via dynamic priorities package.
525 -- Protection: Only written by Self, accessed by anyone
527 Base_CPU
: System
.Multiprocessors
.CPU_Range
;
528 -- Base CPU, only changed via dispatching domains package.
530 -- Protection: Self.L
532 Current_Priority
: System
.Any_Priority
;
533 -- Active priority, except that the effects of protected object
534 -- priority ceilings are not reflected. This only reflects explicit
535 -- priority changes and priority inherited through task activation
538 -- Ada 95 notes: In Ada 95, this field will be transferred to the
539 -- Priority field of an Entry_Calls component when an entry call is
540 -- initiated. The Priority of the Entry_Calls component will not change
541 -- for the duration of the call. The accepting task can use it to boost
542 -- its own priority without fear of its changing in the meantime.
544 -- This can safely be used in the priority ordering of entry queues.
545 -- Once a call is queued, its priority does not change.
547 -- Since an entry call cannot be made while executing a protected
548 -- action, the priority of a task will never reflect a priority ceiling
549 -- change at the point of an entry call.
551 -- Protection: Only written by Self, and only accessed when Acceptor
552 -- accepts an entry or when Created activates, at which points Self is
555 Protected_Action_Nesting
: Natural;
556 pragma Atomic
(Protected_Action_Nesting
);
557 -- The dynamic level of protected action nesting for this task. This
558 -- field is needed for checking whether potentially blocking operations
559 -- are invoked from protected actions. pragma Atomic is used because it
560 -- can be read/written from protected interrupt handlers.
562 Task_Image
: String (1 .. System
.Parameters
.Max_Task_Image_Length
);
563 -- Hold a string that provides a readable id for task, built from the
564 -- variable of which it is a value or component.
566 Task_Image_Len
: Natural;
567 -- Actual length of Task_Image
569 Call
: Entry_Call_Link
;
570 -- The entry call that has been accepted by this task.
572 -- Protection: Self.L. Self will modify this field when Self.Accepting
573 -- is False, and will not need the mutex to do so. Once a task sets
574 -- Pending_ATC_Level = 0, no other task can access this field.
576 LL
: aliased Task_Primitives
.Private_Data
;
577 -- Control block used by the underlying low-level tasking service
580 -- Protection: This is used only by the GNULLI implementation, which
581 -- takes care of all of its synchronization.
583 Task_Arg
: System
.Address
;
584 -- The argument to task procedure. Provide a handle for discriminant
587 -- Protection: Part of the synchronization between Self and Activator.
588 -- Activator writes it, once, before Self starts executing. Thereafter,
589 -- Self only reads it.
591 Task_Alternate_Stack
: System
.Address
;
592 -- The address of the alternate signal stack for this task, if any
594 -- Protection: Only accessed by Self
596 Task_Entry_Point
: Task_Procedure_Access
;
597 -- Information needed to call the procedure containing the code for
598 -- the body of this task.
600 -- Protection: Part of the synchronization between Self and Activator.
601 -- Activator writes it, once, before Self starts executing. Self reads
602 -- it, once, as part of its execution.
604 Compiler_Data
: System
.Soft_Links
.TSD
;
605 -- Task-specific data needed by the compiler to store per-task
608 -- Protection: Only accessed by Self
610 All_Tasks_Link
: Task_Id
;
611 -- Used to link this task to the list of all tasks in the system
613 -- Protection: RTS_Lock
615 Activation_Link
: Task_Id
;
616 -- Used to link this task to a list of tasks to be activated
618 -- Protection: Only used by Activator
621 -- The task that created this task, either by declaring it as a task
622 -- object or by executing a task allocator. The value is null iff Self
623 -- has completed activation.
625 -- Protection: Set by Activator before Self is activated, and only read
626 -- and modified by Self after that.
628 Wait_Count
: Natural;
629 -- This count is used by a task that is waiting for other tasks. At all
630 -- other times, the value should be zero. It is used differently in
631 -- several different states. Since a task cannot be in more than one of
632 -- these states at the same time, a single counter suffices.
634 -- Protection: Self.L
638 -- This is the number of tasks that this task is activating, i.e. the
639 -- children that have started activation but have not completed it.
641 -- Protection: Self.L and Created.L. Both mutexes must be locked, since
642 -- Self.Activation_Count and Created.State must be synchronized.
644 -- Master_Completion_Sleep (phase 1)
646 -- This is the number dependent tasks of a master being completed by
647 -- Self that are activated, but have not yet terminated, and are not
648 -- waiting on a terminate alternative.
650 -- Master_Completion_2_Sleep (phase 2)
652 -- This is the count of tasks dependent on a master being completed by
653 -- Self which are waiting on a terminate alternative.
655 Elaborated
: Access_Boolean
;
656 -- Pointer to a flag indicating that this task's body has been
657 -- elaborated. The flag is created and managed by the
658 -- compiler-generated code.
660 -- Protection: The field itself is only accessed by Activator. The flag
661 -- that it points to is updated by Master and read by Activator; access
662 -- is assumed to be atomic.
664 Activation_Failed
: Boolean;
665 -- Set to True if activation of a chain of tasks fails,
666 -- so that the activator should raise Tasking_Error.
668 Task_Info
: System
.Task_Info
.Task_Info_Type
;
669 -- System-specific attributes of the task as specified by the
672 Analyzer
: System
.Stack_Usage
.Stack_Analyzer
;
673 -- For storing informations used to measure the stack usage
675 Global_Task_Lock_Nesting
: Natural;
676 -- This is the current nesting level of calls to
677 -- System.Tasking.Initialization.Lock_Task. This allows a task to call
678 -- Lock_Task multiple times without deadlocking. A task only locks
679 -- Global_Task_Lock when its Global_Task_Lock_Nesting goes from 0 to 1,
680 -- and only unlocked when it goes from 1 to 0.
682 -- Protection: Only accessed by Self
684 Fall_Back_Handler
: Termination_Handler
;
685 -- This is the fall-back handler that applies to the dependent tasks of
688 -- Protection: Self.L
690 Specific_Handler
: Termination_Handler
;
691 -- This is the specific handler that applies only to this task, and not
692 -- any of its dependent tasks.
694 -- Protection: Self.L
696 Debug_Events
: Debug_Event_Array
;
697 -- Word length array of per task debug events, of which 11 kinds are
698 -- currently defined in System.Tasking.Debugging package.
700 Domain
: Dispatching_Domain_Access
;
701 -- Domain is the dispatching domain to which the task belongs. It is
702 -- only changed via dispatching domains package. This field is made
703 -- part of the Common_ATCB, even when restricted run-times (namely
704 -- Ravenscar) do not use it, because this way the field is always
705 -- available to the underlying layers to set the affinity and we do not
706 -- need to do different things depending on the situation.
708 -- Protection: Self.L
711 ---------------------------------------
712 -- Restricted_Ada_Task_Control_Block --
713 ---------------------------------------
715 -- This type should only be used by the restricted GNARLI and by restricted
716 -- GNULL implementations to allocate an ATCB (see System.Task_Primitives.
717 -- Operations.New_ATCB) that will take significantly less memory.
719 -- Note that the restricted GNARLI should only access fields that are
720 -- present in the Restricted_Ada_Task_Control_Block structure.
722 type Restricted_Ada_Task_Control_Block
(Entry_Num
: Task_Entry_Index
) is
724 Common
: Common_ATCB
;
725 -- The common part between various tasking implementations
727 Entry_Call
: aliased Restricted_Entry_Call_Record
;
728 -- Protection: This field is used on entry call "queues" associated
729 -- with protected objects, and is protected by the protected object
732 pragma Suppress_Initialization
(Restricted_Ada_Task_Control_Block
);
734 Interrupt_Manager_ID
: Task_Id
;
735 -- This task ID is declared here to break circular dependencies.
736 -- Also declare Interrupt_Manager_ID after Task_Id is known, to avoid
737 -- generating unneeded finalization code.
739 -----------------------
740 -- List of all Tasks --
741 -----------------------
743 All_Tasks_List
: Task_Id
;
744 -- Global linked list of all tasks
746 ------------------------------------------
747 -- Regular (non restricted) definitions --
748 ------------------------------------------
750 --------------------------------
751 -- Master Related Definitions --
752 --------------------------------
754 subtype Master_Level
is Integer;
755 subtype Master_ID
is Master_Level
;
757 -- Normally, a task starts out with internal master nesting level one
758 -- larger than external master nesting level. It is incremented to one by
759 -- Enter_Master, which is called in the task body only if the compiler
760 -- thinks the task may have dependent tasks. It is set to 1 for the
761 -- environment task, the level 2 is reserved for server tasks of the
762 -- run-time system (the so called "independent tasks"), and the level 3 is
763 -- for the library level tasks. Foreign threads which are detected by
764 -- the run-time have a level of 0, allowing these tasks to be easily
765 -- distinguished if needed.
767 Foreign_Task_Level
: constant Master_Level
:= 0;
768 Environment_Task_Level
: constant Master_Level
:= 1;
769 Independent_Task_Level
: constant Master_Level
:= 2;
770 Library_Task_Level
: constant Master_Level
:= 3;
776 Unspecified_Priority
: constant Integer := System
.Priority
'First - 1;
778 Priority_Not_Boosted
: constant Integer := System
.Priority
'First - 1;
779 -- Definition of Priority actually has to come from the RTS configuration
781 subtype Rendezvous_Priority
is Integer
782 range Priority_Not_Boosted
.. System
.Any_Priority
'Last;
788 Unspecified_CPU
: constant := -1;
789 -- No affinity specified
791 ------------------------------------
792 -- Rendezvous related definitions --
793 ------------------------------------
795 No_Rendezvous
: constant := 0;
797 Max_Select
: constant Integer := Integer'Last;
800 subtype Select_Index
is Integer range No_Rendezvous
.. Max_Select
;
801 -- type Select_Index is range No_Rendezvous .. Max_Select;
803 subtype Positive_Select_Index
is
804 Select_Index
range 1 .. Select_Index
'Last;
806 type Accept_Alternative
is record
808 S
: Task_Entry_Index
;
812 array (Positive_Select_Index
range <>) of Accept_Alternative
;
814 type Accept_List_Access
is access constant Accept_List
;
816 -----------------------------------
817 -- ATC_Level related definitions --
818 -----------------------------------
820 Max_ATC_Nesting
: constant Natural := 20;
822 subtype ATC_Level_Base
is Integer range 0 .. Max_ATC_Nesting
;
824 ATC_Level_Infinity
: constant ATC_Level_Base
:= ATC_Level_Base
'Last;
826 subtype ATC_Level
is ATC_Level_Base
range 0 .. ATC_Level_Base
'Last - 1;
828 subtype ATC_Level_Index
is ATC_Level
range 1 .. ATC_Level
'Last;
830 ----------------------------------
831 -- Entry_Call_Record definition --
832 ----------------------------------
834 type Entry_Call_Record
is record
840 State
: Entry_Call_State
;
841 pragma Atomic
(State
);
842 -- Indicates part of the state of the call
844 -- Protection: If the call is not on a queue, it should only be
845 -- accessed by Self, and Self does not need any lock to modify this
846 -- field. Once the call is on a queue, the value should be something
847 -- other than Done unless it is cancelled, and access is controller by
848 -- the "server" of the queue -- i.e., the lock of Checked_To_Protection
849 -- (Call_Target) if the call record is on the queue of a PO, or the
850 -- lock of Called_Target if the call is on the queue of a task. See
851 -- comments on type declaration for more details.
853 Uninterpreted_Data
: System
.Address
;
854 -- Data passed by the compiler
856 Exception_To_Raise
: Ada
.Exceptions
.Exception_Id
;
857 -- The exception to raise once this call has been completed without
860 Prev
: Entry_Call_Link
;
862 Next
: Entry_Call_Link
;
865 -- One of Self and Level are redundant in this implementation, since
866 -- each Entry_Call_Record is at Self.Entry_Calls (Level). Since we must
867 -- have access to the entry call record to be reading this, we could
868 -- get Self from Level, or Level from Self. However, this requires
869 -- non-portable address arithmetic.
873 Prio
: System
.Any_Priority
;
875 -- The above fields are those that there may be some hope of packing.
876 -- They are gathered together to allow for compilers that lay records
877 -- out contiguously, to allow for such packing.
879 Called_Task
: Task_Id
;
880 pragma Atomic
(Called_Task
);
881 -- Use for task entry calls. The value is null if the call record is
882 -- not in use. Conversely, unless State is Done and Onqueue is false,
883 -- Called_Task points to an ATCB.
885 -- Protection: Called_Task.L
887 Called_PO
: System
.Address
;
888 pragma Atomic
(Called_PO
);
889 -- Similar to Called_Task but for protected objects
891 -- Note that the previous implementation tried to merge both
892 -- Called_Task and Called_PO but this ended up in many unexpected
893 -- complications (e.g having to add a magic number in the ATCB, which
894 -- caused gdb lots of confusion) with no real gain since the
895 -- Lock_Server implementation still need to loop around chasing for
896 -- pointer changes even with a single pointer.
898 Acceptor_Prev_Call
: Entry_Call_Link
;
899 -- For task entry calls only
901 Acceptor_Prev_Priority
: Rendezvous_Priority
:= Priority_Not_Boosted
;
902 -- For task entry calls only. The priority of the most recent prior
903 -- call being serviced. For protected entry calls, this function should
904 -- be performed by GNULLI ceiling locking.
906 Cancellation_Attempted
: Boolean := False;
907 pragma Atomic
(Cancellation_Attempted
);
908 -- Cancellation of the call has been attempted.
909 -- Consider merging this into State???
911 With_Abort
: Boolean := False;
912 -- Tell caller whether the call may be aborted
913 -- ??? consider merging this with Was_Abortable state
915 Needs_Requeue
: Boolean := False;
916 -- Temporary to tell acceptor of task entry call that
917 -- Exceptional_Complete_Rendezvous needs to do requeue.
920 ------------------------------------
921 -- Task related other definitions --
922 ------------------------------------
924 type Access_Address
is access all System
.Address
;
925 -- Anonymous pointer used to implement task attributes (see s-tataat.adb
928 pragma No_Strict_Aliasing
(Access_Address
);
929 -- This type is used in contexts where aliasing may be an issue (see
930 -- for example s-tataat.adb), so we avoid any incorrect aliasing
933 ----------------------------------------------
934 -- Ada_Task_Control_Block (ATCB) definition --
935 ----------------------------------------------
937 type Entry_Call_Array
is array (ATC_Level_Index
) of
938 aliased Entry_Call_Record
;
940 type Direct_Index
is range 0 .. Parameters
.Default_Attribute_Count
;
941 subtype Direct_Index_Range
is Direct_Index
range 1 .. Direct_Index
'Last;
942 -- Attributes with indexes in this range are stored directly in the task
943 -- control block. Such attributes must be Address-sized. Other attributes
944 -- will be held in dynamically allocated records chained off of the task
947 type Direct_Attribute_Element
is mod Memory_Size
;
948 pragma Atomic
(Direct_Attribute_Element
);
950 type Direct_Attribute_Array
is
951 array (Direct_Index_Range
) of aliased Direct_Attribute_Element
;
953 type Direct_Index_Vector
is mod 2 ** Parameters
.Default_Attribute_Count
;
954 -- This is a bit-vector type, used to store information about
955 -- the usage of the direct attribute fields.
957 type Task_Serial_Number
is mod 2 ** 64;
958 -- Used to give each task a unique serial number
960 type Ada_Task_Control_Block
(Entry_Num
: Task_Entry_Index
) is record
961 Common
: Common_ATCB
;
962 -- The common part between various tasking implementations
964 Entry_Calls
: Entry_Call_Array
;
965 -- An array of entry calls
967 -- Protection: The elements of this array are on entry call queues
968 -- associated with protected objects or task entries, and are protected
969 -- by the protected object lock or Acceptor.L, respectively.
971 Entry_Names
: Entry_Names_Array_Access
:= null;
972 -- An array of string names which denotes entry [family member] names.
973 -- The structure is indexed by task entry index and contains Entry_Num
976 New_Base_Priority
: System
.Any_Priority
;
977 -- New value for Base_Priority (for dynamic priorities package)
979 -- Protection: Self.L
981 Open_Accepts
: Accept_List_Access
;
982 -- This points to the Open_Accepts array of accept alternatives passed
983 -- to the RTS by the compiler-generated code to Selective_Wait. It is
984 -- non-null iff this task is ready to accept an entry call.
986 -- Protection: Self.L
988 Chosen_Index
: Select_Index
;
989 -- The index in Open_Accepts of the entry call accepted by a selective
990 -- wait executed by this task.
992 -- Protection: Written by both Self and Caller. Usually protected by
993 -- Self.L. However, once the selection is known to have been written it
994 -- can be accessed without protection. This happens after Self has
995 -- updated it itself using information from a suspended Caller, or
996 -- after Caller has updated it and awakened Self.
998 Master_of_Task
: Master_Level
;
999 -- The task executing the master of this task, and the ID of this task's
1000 -- master (unique only among masters currently active within Parent).
1002 -- Protection: Set by Activator before Self is activated, and read
1003 -- after Self is activated.
1005 Master_Within
: Master_Level
;
1006 -- The ID of the master currently executing within this task; that is,
1007 -- the most deeply nested currently active master.
1009 -- Protection: Only written by Self, and only read by Self or by
1010 -- dependents when Self is attempting to exit a master. Since Self will
1011 -- not write this field until the master is complete, the
1012 -- synchronization should be adequate to prevent races.
1014 Alive_Count
: Natural := 0;
1015 -- Number of tasks directly dependent on this task (including itself)
1016 -- that are still "alive", i.e. not terminated.
1018 -- Protection: Self.L
1020 Awake_Count
: Natural := 0;
1021 -- Number of tasks directly dependent on this task (including itself)
1022 -- still "awake", i.e., are not terminated and not waiting on a
1023 -- terminate alternative.
1025 -- Invariant: Awake_Count <= Alive_Count
1027 -- Protection: Self.L
1029 -- Beginning of flags
1031 Aborting
: Boolean := False;
1032 pragma Atomic
(Aborting
);
1033 -- Self is in the process of aborting. While set, prevents multiple
1034 -- abort signals from being sent by different aborter while abort
1035 -- is acted upon. This is essential since an aborter which calls
1036 -- Abort_To_Level could set the Pending_ATC_Level to yet a lower level
1037 -- (than the current level), may be preempted and would send the
1038 -- abort signal when resuming execution. At this point, the abortee
1039 -- may have completed abort to the proper level such that the
1040 -- signal (and resulting abort exception) are not handled any more.
1041 -- In other words, the flag prevents a race between multiple aborters
1043 -- Protection: protected by atomic access.
1045 ATC_Hack
: Boolean := False;
1046 pragma Atomic
(ATC_Hack
);
1048 -- Temporary fix, to allow Undefer_Abort to reset Aborting in the
1049 -- handler for Abort_Signal that encloses an async. entry call.
1050 -- For the longer term, this should be done via code in the
1053 Callable
: Boolean := True;
1054 -- It is OK to call entries of this task
1056 Dependents_Aborted
: Boolean := False;
1057 -- This is set to True by whichever task takes responsibility for
1058 -- aborting the dependents of this task.
1060 -- Protection: Self.L
1062 Interrupt_Entry
: Boolean := False;
1063 -- Indicates if one or more Interrupt Entries are attached to the task.
1064 -- This flag is needed for cleaning up the Interrupt Entry bindings.
1066 Pending_Action
: Boolean := False;
1067 -- Unified flag indicating some action needs to be take when abort
1068 -- next becomes undeferred. Currently set if:
1069 -- . Pending_Priority_Change is set
1070 -- . Pending_ATC_Level is changed
1071 -- . Requeue involving POs
1072 -- (Abortable field may have changed and the Wait_Until_Abortable
1073 -- has to recheck the abortable status of the call.)
1074 -- . Exception_To_Raise is non-null
1076 -- Protection: Self.L
1078 -- This should never be reset back to False outside of the procedure
1079 -- Do_Pending_Action, which is called by Undefer_Abort. It should only
1080 -- be set to True by Set_Priority and Abort_To_Level.
1082 Pending_Priority_Change
: Boolean := False;
1083 -- Flag to indicate pending priority change (for dynamic priorities
1084 -- package). The base priority is updated on the next abort
1085 -- completion point (aka. synchronization point).
1087 -- Protection: Self.L
1089 Terminate_Alternative
: Boolean := False;
1090 -- Task is accepting Select with Terminate Alternative
1092 -- Protection: Self.L
1096 -- Beginning of counts
1098 ATC_Nesting_Level
: ATC_Level
:= 1;
1099 -- The dynamic level of ATC nesting (currently executing nested
1100 -- asynchronous select statements) in this task.
1102 -- Protection: Self_ID.L. Only Self reads or updates this field.
1103 -- Decrementing it deallocates an Entry_Calls component, and care must
1104 -- be taken that all references to that component are eliminated before
1105 -- doing the decrement. This in turn will require locking a protected
1106 -- object (for a protected entry call) or the Acceptor's lock (for a
1107 -- task entry call). No other task should attempt to read or modify
1110 Deferral_Level
: Natural := 1;
1111 -- This is the number of times that Defer_Abort has been called by
1112 -- this task without a matching Undefer_Abort call. Abortion is only
1113 -- allowed when this zero. It is initially 1, to protect the task at
1116 -- Protection: Only updated by Self; access assumed to be atomic
1118 Pending_ATC_Level
: ATC_Level_Base
:= ATC_Level_Infinity
;
1119 -- The ATC level to which this task is currently being aborted. If the
1120 -- value is zero, the entire task has "completed". That may be via
1121 -- abort, exception propagation, or normal exit. If the value is
1122 -- ATC_Level_Infinity, the task is not being aborted to any level. If
1123 -- the value is positive, the task has not completed. This should ONLY
1124 -- be modified by Abort_To_Level and Exit_One_ATC_Level.
1126 -- Protection: Self.L
1128 Serial_Number
: Task_Serial_Number
;
1129 -- Monotonic counter to provide some way to check locking rules/ordering
1131 Known_Tasks_Index
: Integer := -1;
1132 -- Index in the System.Tasking.Debug.Known_Tasks array
1134 User_State
: Long_Integer := 0;
1135 -- User-writeable location, for use in debugging tasks; also provides a
1136 -- simple task specific data.
1138 Direct_Attributes
: Direct_Attribute_Array
;
1139 -- For task attributes that have same size as Address
1141 Is_Defined
: Direct_Index_Vector
:= 0;
1142 -- Bit I is 1 iff Direct_Attributes (I) is defined
1144 Indirect_Attributes
: Access_Address
;
1145 -- A pointer to chain of records for other attributes that are not
1146 -- address-sized, including all tagged types.
1148 Entry_Queues
: Task_Entry_Queue_Array
(1 .. Entry_Num
);
1149 -- An array of task entry queues
1151 -- Protection: Self.L. Once a task has set Self.Stage to Completing, it
1152 -- has exclusive access to this field.
1154 Free_On_Termination
: Boolean := False;
1155 -- Deallocate the ATCB when the task terminates. This flag is normally
1156 -- False, and is set True when Unchecked_Deallocation is called on a
1157 -- non-terminated task so that the associated storage is automatically
1158 -- reclaimed when the task terminates.
1161 --------------------
1162 -- Initialization --
1163 --------------------
1165 procedure Initialize
;
1166 -- This procedure constitutes the first part of the initialization of the
1167 -- GNARL. This includes creating data structures to make the initial thread
1168 -- into the environment task. The last part of the initialization is done
1169 -- in System.Tasking.Initialization or System.Tasking.Restricted.Stages.
1170 -- All the initializations used to be in Tasking.Initialization, but this
1171 -- is no longer possible with the run time simplification (including
1172 -- optimized PO and the restricted run time) since one cannot rely on
1173 -- System.Tasking.Initialization being present, as was done before.
1175 procedure Initialize_ATCB
1177 Task_Entry_Point
: Task_Procedure_Access
;
1178 Task_Arg
: System
.Address
;
1180 Elaborated
: Access_Boolean
;
1181 Base_Priority
: System
.Any_Priority
;
1182 Base_CPU
: System
.Multiprocessors
.CPU_Range
;
1183 Domain
: Dispatching_Domain_Access
;
1184 Task_Info
: System
.Task_Info
.Task_Info_Type
;
1185 Stack_Size
: System
.Parameters
.Size_Type
;
1187 Success
: out Boolean);
1188 -- Initialize fields of a TCB and link into global TCB structures Call
1189 -- this only with abort deferred and holding RTS_Lock. Need more
1190 -- documentation, mention T, and describe Success ???
1194 Null_Task
: constant Task_Id
:= null;
1196 type Activation_Chain
is limited record
1200 -- Activation_Chain is an in-out parameter of initialization procedures and
1201 -- it must be passed by reference because the init proc may terminate
1202 -- abnormally after creating task components, and these must be properly
1203 -- registered for removal (Expunge_Unactivated_Tasks). The "limited" forces
1204 -- Activation_Chain to be a by-reference type; see RM-6.2(4).