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Wrap

Text File | 2000-07-19 | 13KB | 275 lines

------------------------------------------------------------------------------ -- -- -- 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: 1.33 $ -- -- -- 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 sucessfully 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;