1------------------------------------------------------------------------------ 2-- -- 3-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS -- 4-- -- 5-- S Y S T E M . T A S K I N G . S T A G E S -- 6-- -- 7-- S p e c -- 8-- -- 9-- Copyright (C) 1992-2019, Free Software Foundation, Inc. -- 10-- -- 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. -- 17-- -- 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. -- 21-- -- 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/>. -- 26-- -- 27-- GNARL was developed by the GNARL team at Florida State University. -- 28-- Extensive contributions were provided by Ada Core Technologies, Inc. -- 29-- -- 30------------------------------------------------------------------------------ 31 32-- This package represents the high level tasking interface used by the 33-- compiler to expand Ada 95 tasking constructs into simpler run time calls 34-- (aka GNARLI, GNU Ada Run-time Library Interface) 35 36-- Note: Only the compiler is allowed to use this interface, by generating 37-- direct calls to it, via Rtsfind. 38 39-- Any changes to this interface may require corresponding compiler changes 40-- in exp_ch9.adb and possibly exp_ch7.adb 41 42with System.Task_Info; 43with System.Parameters; 44 45with Ada.Real_Time; 46 47package System.Tasking.Stages is 48 pragma Elaborate_Body; 49 50 -- The compiler will expand in the GNAT tree the following construct: 51 52 -- task type T (Discr : Integer); 53 54 -- task body T is 55 -- ...declarations, possibly some controlled... 56 -- begin 57 -- ...B...; 58 -- end T; 59 60 -- T1 : T (1); 61 62 -- as follows: 63 64 -- enter_master.all; 65 66 -- _chain : aliased activation_chain; 67 -- activation_chainIP (_chain); 68 69 -- task type t (discr : integer); 70 -- tE : aliased boolean := false; 71 -- tZ : size_type := unspecified_size; 72 -- type tV (discr : integer) is limited record 73 -- _task_id : task_id; 74 -- end record; 75 -- procedure tB (_task : access tV); 76 -- freeze tV [ 77 -- procedure tVIP (_init : in out tV; _master : master_id; 78 -- _chain : in out activation_chain; _task_id : in task_image_type; 79 -- discr : integer) is 80 -- begin 81 -- _init.discr := discr; 82 -- _init._task_id := null; 83 -- create_task (unspecified_priority, tZ, 84 -- unspecified_task_info, unspecified_cpu, 85 -- ada__real_time__time_span_zero, 0, _master, 86 -- task_procedure_access!(tB'address), _init'address, 87 -- tE'unchecked_access, _chain, _task_id, _init._task_id); 88 -- return; 89 -- end tVIP; 90 -- ] 91 92 -- procedure tB (_task : access tV) is 93 -- discr : integer renames _task.discr; 94 95 -- procedure _clean is 96 -- begin 97 -- abort_defer.all; 98 -- complete_task; 99 -- finalize_list (F14b); 100 -- abort_undefer.all; 101 -- return; 102 -- end _clean; 103 -- begin 104 -- abort_undefer.all; 105 -- ...declarations... 106 -- complete_activation; 107 -- ...B...; 108 -- return; 109 -- at end 110 -- _clean; 111 -- end tB; 112 113 -- tE := true; 114 -- t1 : t (1); 115 -- _master : constant master_id := current_master.all; 116 -- t1S : task_image_type := new string'"t1"; 117 -- task_image_typeIP (t1, _master, _chain, t1S, 1); 118 119 -- activate_tasks (_chain'unchecked_access); 120 121 procedure Abort_Tasks (Tasks : Task_List); 122 -- Compiler interface only. Do not call from within the RTS. Initiate 123 -- abort, however, the actual abort is done by abortee by means of 124 -- Abort_Handler and Abort_Undefer 125 -- 126 -- source code: 127 -- Abort T1, T2; 128 -- code expansion: 129 -- abort_tasks (task_list'(t1._task_id, t2._task_id)); 130 131 procedure Activate_Tasks (Chain_Access : Activation_Chain_Access); 132 -- Compiler interface only. Do not call from within the RTS. 133 -- This must be called by the creator of a chain of one or more new tasks, 134 -- to activate them. The chain is a linked list that up to this point is 135 -- only known to the task that created them, though the individual tasks 136 -- are already in the All_Tasks_List. 137 -- 138 -- The compiler builds the chain in LIFO order (as a stack). Another 139 -- version of this procedure had code to reverse the chain, so as to 140 -- activate the tasks in the order of declaration. This might be nice, but 141 -- it is not needed if priority-based scheduling is supported, since all 142 -- the activated tasks synchronize on the activators lock before they 143 -- start activating and so they should start activating in priority order. 144 -- ??? Actually, the body of this package DOES reverse the chain, so I 145 -- don't understand the above comment. 146 147 procedure Complete_Activation; 148 -- Compiler interface only. Do not call from within the RTS. 149 -- This should be called from the task body at the end of 150 -- the elaboration code for its declarative part. 151 -- Decrement the count of tasks to be activated by the activator and 152 -- wake it up so it can check to see if all tasks have been activated. 153 -- Except for the environment task, which should never call this procedure, 154 -- T.Activator should only be null iff T has completed activation. 155 156 procedure Complete_Master; 157 -- Compiler interface only. Do not call from within the RTS. This must 158 -- be called on exit from any master where Enter_Master was called. 159 -- Assume abort is deferred at this point. 160 161 procedure Complete_Task; 162 -- Compiler interface only. Do not call from within the RTS. 163 -- This should be called from an implicit at-end handler 164 -- associated with the task body, when it completes. 165 -- From this point, the current task will become not callable. 166 -- If the current task have not completed activation, this should be done 167 -- now in order to wake up the activator (the environment task). 168 169 procedure Create_Task 170 (Priority : Integer; 171 Stack_Size : System.Parameters.Size_Type; 172 Secondary_Stack_Size : System.Parameters.Size_Type; 173 Task_Info : System.Task_Info.Task_Info_Type; 174 CPU : Integer; 175 Relative_Deadline : Ada.Real_Time.Time_Span; 176 Domain : Dispatching_Domain_Access; 177 Num_Entries : Task_Entry_Index; 178 Master : Master_Level; 179 State : Task_Procedure_Access; 180 Discriminants : System.Address; 181 Elaborated : Access_Boolean; 182 Chain : in out Activation_Chain; 183 Task_Image : String; 184 Created_Task : out Task_Id); 185 -- Compiler interface only. Do not call from within the RTS. 186 -- This must be called to create a new task. 187 -- 188 -- Priority is the task's priority (assumed to be in range of type 189 -- System.Any_Priority) 190 -- 191 -- Stack_Size is the stack size of the task to create 192 -- 193 -- Secondary_Stack_Size is the size of the secondary stack to be used by 194 -- the task. 195 -- 196 -- Task_Info is the task info associated with the created task, or 197 -- Unspecified_Task_Info if none. 198 -- 199 -- CPU is the task affinity. Passed as an Integer because the undefined 200 -- value is not in the range of CPU_Range. Static range checks are 201 -- performed when analyzing the pragma, and dynamic ones are performed 202 -- before setting the affinity at run time. 203 -- 204 -- Relative_Deadline is the relative deadline associated with the created 205 -- task by means of a pragma Relative_Deadline, or 0.0 if none. 206 -- 207 -- Domain is the dispatching domain associated with the created task by 208 -- means of a Dispatching_Domain pragma or aspect, or null if none. 209 -- 210 -- State is the compiler generated task's procedure body 211 -- 212 -- Discriminants is a pointer to a limited record whose discriminants 213 -- are those of the task to create. This parameter should be passed as 214 -- the single argument to State. 215 -- 216 -- Elaborated is a pointer to a Boolean that must be set to true on exit 217 -- if the task could be successfully elaborated. 218 -- 219 -- Chain is a linked list of task that needs to be created. On exit, 220 -- Created_Task.Activation_Link will be Chain.T_ID, and Chain.T_ID 221 -- will be Created_Task (e.g the created task will be linked at the front 222 -- of Chain). 223 -- 224 -- Task_Image is a string created by the compiler that the 225 -- run time can store to ease the debugging and the 226 -- Ada.Task_Identification facility. 227 -- 228 -- Created_Task is the resulting task. 229 -- 230 -- This procedure can raise Storage_Error if the task creation failed. 231 232 function Current_Master return Master_Level; 233 -- Compiler interface only. 234 -- This is called to obtain the current master nesting level. 235 236 procedure Enter_Master; 237 -- Compiler interface only. Do not call from within the RTS. 238 -- This must be called on entry to any "master" where a task, 239 -- or access type designating objects containing tasks, may be 240 -- declared. 241 242 procedure Expunge_Unactivated_Tasks (Chain : in out Activation_Chain); 243 -- Compiler interface only. Do not call from within the RTS. 244 -- This must be called by the compiler-generated code for an allocator if 245 -- the allocated object contains tasks, if the allocator exits without 246 -- calling Activate_Tasks for a given activation chains, as can happen if 247 -- an exception occurs during initialization of the object. 248 -- 249 -- This should be called ONLY for tasks created via an allocator. Recovery 250 -- of storage for unactivated local task declarations is done by 251 -- Complete_Master and Complete_Task. 252 -- 253 -- We remove each task from Chain and All_Tasks_List before we free the 254 -- storage of its ATCB. 255 -- 256 -- In other places where we recover the storage of unactivated tasks, we 257 -- need to clean out the entry queues, but here that should not be 258 -- necessary, since these tasks should not have been visible to any other 259 -- tasks, and so no task should be able to queue a call on their entries. 260 -- 261 -- Just in case somebody misuses this subprogram, there is a check to 262 -- verify this condition. 263 264 procedure Finalize_Global_Tasks; 265 -- This should be called to complete the execution of the environment task 266 -- and shut down the tasking runtime system. It is the equivalent of 267 -- Complete_Task, but for the environment task. 268 -- 269 -- The environment task must first call Complete_Master, to wait for user 270 -- tasks that depend on library-level packages to terminate. It then calls 271 -- Abort_Dependents to abort the "independent" library-level server tasks 272 -- that are created implicitly by the RTS packages (signal and timer server 273 -- tasks), and then waits for them to terminate. Then, it calls 274 -- Vulnerable_Complete_Task. 275 -- 276 -- It currently also executes the global finalization list, and then resets 277 -- the "soft links". 278 279 procedure Free_Task (T : Task_Id); 280 -- Recover all runtime system storage associated with the task T, but only 281 -- if T has terminated. Do nothing in the other case. It is called from 282 -- Unchecked_Deallocation, for objects that are or contain tasks. 283 284 procedure Move_Activation_Chain 285 (From, To : Activation_Chain_Access; 286 New_Master : Master_ID); 287 -- Compiler interface only. Do not call from within the RTS. 288 -- Move all tasks on From list to To list, and change their Master_Of_Task 289 -- to be New_Master. This is used to implement build-in-place function 290 -- returns. Tasks that are part of the return object are initially placed 291 -- on an activation chain local to the return statement, and their master 292 -- is the return statement, in case the return statement is left 293 -- prematurely (due to raising an exception, being aborted, or a goto or 294 -- exit statement). Once the return statement has completed successfully, 295 -- Move_Activation_Chain is called to move them to the caller's activation 296 -- chain, and change their master to the one passed in by the caller. If 297 -- that doesn't happen, they will never be activated, and will become 298 -- terminated on leaving the return statement. 299 300 function Terminated (T : Task_Id) return Boolean; 301 -- This is called by the compiler to implement the 'Terminated attribute. 302 -- Though is not required to be so by the ARM, we choose to synchronize 303 -- with the task's ATCB, so that this is more useful for polling the state 304 -- of a task, and so that it becomes an abort completion point for the 305 -- calling task (via Undefer_Abort). 306 -- 307 -- source code: 308 -- T1'Terminated 309 -- 310 -- code expansion: 311 -- terminated (t1._task_id) 312 313 procedure Terminate_Task (Self_ID : Task_Id); 314 -- Terminate the calling task. 315 -- This should only be called by the Task_Wrapper procedure, and to 316 -- deallocate storage associate with foreign tasks. 317 318end System.Tasking.Stages; 319