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------------------------------------------------------------------------------ -- -- -- GNAT 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 -- -- -- -- Copyright (C) 1992-2009, 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 3, or (at your option) any later ver- -- -- sion. GNAT 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. -- -- -- -- As a special exception under Section 7 of GPL version 3, you are granted -- -- additional permissions described in the GCC Runtime Library Exception, -- -- version 3.1, as published by the Free Software Foundation. -- -- -- -- You should have received a copy of the GNU General Public License and -- -- a copy of the GCC Runtime Library Exception along with this program; -- -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- -- <http://www.gnu.org/licenses/>. -- -- -- -- GNARL was developed by the GNARL team at Florida State University. -- -- Extensive contributions were provided by Ada Core Technologies, Inc. -- -- -- ------------------------------------------------------------------------------ -- 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; with System.Parameters; with Ada.Real_Time; 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; -- activation_chainIP (_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 tVIP (_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, ada__real_time__time_span_zero, 0, -- _master, task_procedure_access!(tB'address), -- _init'address, tE'unchecked_access, _chain, _task_id, _init. -- _task_id); -- return; -- end tVIP; -- ] -- 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; -- t1S : task_image_type := new string'"t1"; -- task_image_typeIP (t1, _master, _chain, t1S, 1); -- activate_tasks (_chain'unchecked_access); procedure Abort_Tasks (Tasks : Task_List); -- Compiler interface only. Do not call from within the RTS. Initiate -- abort, however, the actual abort 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. -- ??? Actually, the body of this package DOES reverse the chain, so I -- don't understand the above comment. 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; Relative_Deadline : Ada.Real_Time.Time_Span; 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 : String; Created_Task : out Task_Id; Build_Entry_Names : Boolean); -- 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. -- Relative_Deadline is the relative deadline associated with the created -- task by means of a pragma Relative_Deadline, or 0.0 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 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. -- Build_Entry_Names is a flag which controls the allocation of the data -- structure which stores all entry names. -- -- 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. procedure Move_Activation_Chain (From, To : Activation_Chain_Access; New_Master : Master_ID); -- Compiler interface only. Do not call from within the RTS. -- Move all tasks on From list to To list, and change their Master_of_Task -- to be New_Master. This is used to implement build-in-place function -- returns. Tasks that are part of the return object are initially placed -- on an activation chain local to the return statement, and their master -- is the return statement, in case the return statement is left -- prematurely (due to raising an exception, being aborted, or a goto or -- exit statement). Once the return statement has completed successfully, -- Move_Activation_Chain is called to move them to the caller's activation -- chain, and change their master to the one passed in by the caller. If -- that doesn't happen, they will never be activated, and will become -- terminated on leaving the return statement. procedure Set_Entry_Name (T : Task_Id; Pos : Task_Entry_Index; Val : String_Access); -- This is called by the compiler to map a string which denotes an entry -- name to a task entry index. 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) procedure Terminate_Task (Self_ID : Task_Id); -- Terminate the calling task. -- This should only be called by the Task_Wrapper procedure, and to -- deallocate storage associate with foreign tasks. end System.Tasking.Stages;
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