| ------------------------------------------------------------------------------ |
| -- -- |
| -- GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS -- |
| -- -- |
| -- S Y S T E M . T A S K I N G . S T A G E S -- |
| -- -- |
| -- S p e c -- |
| -- -- |
| -- $Revision: 1.1 $ |
| -- -- |
| -- Copyright (C) 1992-1999, Free Software Foundation, Inc. -- |
| -- -- |
| -- GNARL is free software; you can redistribute it and/or modify it under -- |
| -- terms of the GNU General Public License as published by the Free Soft- -- |
| -- ware Foundation; either version 2, or (at your option) any later ver- -- |
| -- sion. GNARL is distributed in the hope that it will be useful, but WITH- -- |
| -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- |
| -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- |
| -- for more details. You should have received a copy of the GNU General -- |
| -- Public License distributed with GNARL; see file COPYING. If not, write -- |
| -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, -- |
| -- MA 02111-1307, USA. -- |
| -- -- |
| -- As a special exception, if other files instantiate generics from this -- |
| -- unit, or you link this unit with other files to produce an executable, -- |
| -- this unit does not by itself cause the resulting executable to be -- |
| -- covered by the GNU General Public License. This exception does not -- |
| -- however invalidate any other reasons why the executable file might be -- |
| -- covered by the GNU Public License. -- |
| -- -- |
| -- GNARL was developed by the GNARL team at Florida State University. It is -- |
| -- now maintained by Ada Core Technologies Inc. in cooperation with Florida -- |
| -- State University (http://www.gnat.com). -- |
| -- -- |
| ------------------------------------------------------------------------------ |
| |
| -- This package represents the high level tasking interface used by the |
| -- compiler to expand Ada 95 tasking constructs into simpler run time calls |
| -- (aka GNARLI, GNU Ada Run-time Library Interface) |
| |
| -- Note: Only the compiler is allowed to use this interface, by generating |
| -- direct calls to it, via Rtsfind. |
| -- Any changes to this interface may require corresponding compiler changes |
| -- in exp_ch9.adb and possibly exp_ch7.adb |
| |
| with System.Task_Info; |
| -- used for Task_Info_Type |
| |
| with System.Parameters; |
| -- used for Size_Type |
| |
| package System.Tasking.Stages is |
| pragma Elaborate_Body; |
| |
| -- The compiler will expand in the GNAT tree the following construct: |
| -- |
| -- task type T (Discr : Integer); |
| -- |
| -- task body T is |
| -- ...declarations, possibly some controlled... |
| -- begin |
| -- ...B...; |
| -- end T; |
| -- |
| -- T1 : T (1); |
| -- |
| -- as follows: |
| -- |
| -- enter_master.all; |
| -- |
| -- _chain : aliased activation_chain; |
| -- _init_proc (_chain); |
| -- |
| -- task type t (discr : integer); |
| -- tE : aliased boolean := false; |
| -- tZ : size_type := unspecified_size; |
| -- type tV (discr : integer) is limited record |
| -- _task_id : task_id; |
| -- end record; |
| -- procedure tB (_task : access tV); |
| -- freeze tV [ |
| -- procedure _init_proc (_init : in out tV; _master : master_id; |
| -- _chain : in out activation_chain; _task_id : in task_image_type; |
| -- discr : integer) is |
| -- begin |
| -- _init.discr := discr; |
| -- _init._task_id := null; |
| -- create_task (unspecified_priority, tZ, |
| -- unspecified_task_info, 0, _master, |
| -- task_procedure_access!(tB'address), |
| -- _init'address, tE'unchecked_access, _chain, _task_id, _init. |
| -- _task_id); |
| -- return; |
| -- end _init_proc; |
| -- ] |
| -- |
| -- procedure tB (_task : access tV) is |
| -- discr : integer renames _task.discr; |
| -- |
| -- procedure _clean is |
| -- begin |
| -- abort_defer.all; |
| -- complete_task; |
| -- finalize_list (F14b); |
| -- abort_undefer.all; |
| -- return; |
| -- end _clean; |
| -- begin |
| -- abort_undefer.all; |
| -- ...declarations... |
| -- complete_activation; |
| -- ...B...; |
| -- return; |
| -- at end |
| -- _clean; |
| -- end tB; |
| -- |
| -- tE := true; |
| -- t1 : t (1); |
| -- master : constant master_id := current_master.all; |
| -- t1I : task_image_type := new string'"t1"; |
| -- _init_proc (t1, _master, _chain, t1I, 1); |
| -- |
| -- activate_tasks (_chain'unchecked_access); |
| |
| procedure Abort_Tasks (Tasks : Task_List); |
| -- Compiler interface only. Do not call from within the RTS. |
| -- Initiate abortion, however, the actual abortion is done by abortee by |
| -- means of Abort_Handler and Abort_Undefer |
| -- |
| -- source code: |
| -- Abort T1, T2; |
| -- code expansion: |
| -- abort_tasks (task_list'(t1._task_id, t2._task_id)); |
| |
| procedure Activate_Tasks (Chain_Access : Activation_Chain_Access); |
| -- Compiler interface only. Do not call from within the RTS. |
| -- This must be called by the creator of a chain of one or more new tasks, |
| -- to activate them. The chain is a linked list that up to this point is |
| -- only known to the task that created them, though the individual tasks |
| -- are already in the All_Tasks_List. |
| -- |
| -- The compiler builds the chain in LIFO order (as a stack). Another |
| -- version of this procedure had code to reverse the chain, so as to |
| -- activate the tasks in the order of declaration. This might be nice, but |
| -- it is not needed if priority-based scheduling is supported, since all |
| -- the activated tasks synchronize on the activators lock before they |
| -- start activating and so they should start activating in priority order. |
| |
| procedure Complete_Activation; |
| -- Compiler interface only. Do not call from within the RTS. |
| -- This should be called from the task body at the end of |
| -- the elaboration code for its declarative part. |
| -- Decrement the count of tasks to be activated by the activator and |
| -- wake it up so it can check to see if all tasks have been activated. |
| -- Except for the environment task, which should never call this procedure, |
| -- T.Activator should only be null iff T has completed activation. |
| |
| procedure Complete_Master; |
| -- Compiler interface only. Do not call from within the RTS. This must |
| -- be called on exit from any master where Enter_Master was called. |
| -- Assume abort is deferred at this point. |
| |
| procedure Complete_Task; |
| -- Compiler interface only. Do not call from within the RTS. |
| -- This should be called from an implicit at-end handler |
| -- associated with the task body, when it completes. |
| -- From this point, the current task will become not callable. |
| -- If the current task have not completed activation, this should be done |
| -- now in order to wake up the activator (the environment task). |
| |
| procedure Create_Task |
| (Priority : Integer; |
| Size : System.Parameters.Size_Type; |
| Task_Info : System.Task_Info.Task_Info_Type; |
| Num_Entries : Task_Entry_Index; |
| Master : Master_Level; |
| State : Task_Procedure_Access; |
| Discriminants : System.Address; |
| Elaborated : Access_Boolean; |
| Chain : in out Activation_Chain; |
| Task_Image : System.Task_Info.Task_Image_Type; |
| Created_Task : out Task_ID); |
| -- Compiler interface only. Do not call from within the RTS. |
| -- This must be called to create a new task. |
| -- |
| -- Priority is the task's priority (assumed to be in the |
| -- System.Any_Priority'Range) |
| -- Size is the stack size of the task to create |
| -- Task_Info is the task info associated with the created task, or |
| -- Unspecified_Task_Info if none. |
| -- State is the compiler generated task's procedure body |
| -- Discriminants is a pointer to a limited record whose discriminants |
| -- are those of the task to create. This parameter should be passed as |
| -- the single argument to State. |
| -- Elaborated is a pointer to a Boolean that must be set to true on exit |
| -- if the task could be successfully elaborated. |
| -- Chain is a linked list of task that needs to be created. On exit, |
| -- Created_Task.Activation_Link will be Chain.T_ID, and Chain.T_ID |
| -- will be Created_Task (e.g the created task will be linked at the front |
| -- of Chain). |
| -- Task_Image is a pointer to a string created by the compiler that the |
| -- run time can store to ease the debugging and the |
| -- Ada.Task_Identification facility. |
| -- Created_Task is the resulting task. |
| -- |
| -- This procedure can raise Storage_Error if the task creation failed. |
| |
| function Current_Master return Master_Level; |
| -- Compiler interface only. |
| -- This is called to obtain the current master nesting level. |
| |
| procedure Enter_Master; |
| -- Compiler interface only. Do not call from within the RTS. |
| -- This must be called on entry to any "master" where a task, |
| -- or access type designating objects containing tasks, may be |
| -- declared. |
| |
| procedure Expunge_Unactivated_Tasks (Chain : in out Activation_Chain); |
| -- Compiler interface only. Do not call from within the RTS. |
| -- This must be called by the compiler-generated code for an allocator if |
| -- the allocated object contains tasks, if the allocator exits without |
| -- calling Activate_Tasks for a given activation chains, as can happen if |
| -- an exception occurs during initialization of the object. |
| -- |
| -- This should be called ONLY for tasks created via an allocator. Recovery |
| -- of storage for unactivated local task declarations is done by |
| -- Complete_Master and Complete_Task. |
| -- |
| -- We remove each task from Chain and All_Tasks_List before we free the |
| -- storage of its ATCB. |
| -- |
| -- In other places where we recover the storage of unactivated tasks, we |
| -- need to clean out the entry queues, but here that should not be |
| -- necessary, since these tasks should not have been visible to any other |
| -- tasks, and so no task should be able to queue a call on their entries. |
| -- |
| -- Just in case somebody misuses this subprogram, there is a check to |
| -- verify this condition. |
| |
| procedure Finalize_Global_Tasks; |
| -- This should be called to complete the execution of the environment task |
| -- and shut down the tasking runtime system. It is the equivalent of |
| -- Complete_Task, but for the environment task. |
| -- |
| -- The environment task must first call Complete_Master, to wait for user |
| -- tasks that depend on library-level packages to terminate. It then calls |
| -- Abort_Dependents to abort the "independent" library-level server tasks |
| -- that are created implicitly by the RTS packages (signal and timer server |
| -- tasks), and then waits for them to terminate. Then, it calls |
| -- Vulnerable_Complete_Task. |
| -- |
| -- It currently also executes the global finalization list, and then resets |
| -- the "soft links". |
| |
| procedure Free_Task (T : Task_ID); |
| -- Recover all runtime system storage associated with the task T, but only |
| -- if T has terminated. Do nothing in the other case. It is called from |
| -- Unchecked_Deallocation, for objects that are or contain tasks. |
| |
| function Terminated (T : Task_ID) return Boolean; |
| -- This is called by the compiler to implement the 'Terminated attribute. |
| -- Though is not required to be so by the ARM, we choose to synchronize |
| -- with the task's ATCB, so that this is more useful for polling the state |
| -- of a task, and so that it becomes an abort completion point for the |
| -- calling task (via Undefer_Abort). |
| -- |
| -- source code: |
| -- T1'Terminated |
| -- |
| -- code expansion: |
| -- terminated (t1._task_id) |
| |
| end System.Tasking.Stages; |
