1------------------------------------------------------------------------------ 2-- -- 3-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS -- 4-- -- 5-- SYSTEM.TASKING.PROTECTED_OBJECTS.SINGLE_ENTRY -- 6-- -- 7-- B o d y -- 8-- -- 9-- Copyright (C) 1998-2021, 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 32pragma Style_Checks (All_Checks); 33-- Turn off subprogram ordering check, since restricted GNARLI subprograms are 34-- gathered together at end. 35 36-- This package provides an optimized version of Protected_Objects.Operations 37-- and Protected_Objects.Entries making the following assumptions: 38 39-- PO has only one entry 40-- There is only one caller at a time (No_Entry_Queue) 41-- There is no dynamic priority support (No_Dynamic_Priorities) 42-- No Abort Statements 43-- (No_Abort_Statements, Max_Asynchronous_Select_Nesting => 0) 44-- PO are at library level 45-- No Requeue 46-- None of the tasks will terminate (no need for finalization) 47 48-- This interface is intended to be used in the ravenscar and restricted 49-- profiles, the compiler is responsible for ensuring that the conditions 50-- mentioned above are respected, except for the No_Entry_Queue restriction 51-- that is checked dynamically in this package, since the check cannot be 52-- performed at compile time, and is relatively cheap (see PO_Do_Or_Queue, 53-- Service_Entry). 54 55pragma Suppress (All_Checks); 56-- Why is this required ??? 57 58with Ada.Exceptions; 59 60with System.Task_Primitives.Operations; 61 62package body System.Tasking.Protected_Objects.Single_Entry is 63 64 package STPO renames System.Task_Primitives.Operations; 65 66 ----------------------- 67 -- Local Subprograms -- 68 ----------------------- 69 70 procedure Send_Program_Error (Entry_Call : Entry_Call_Link); 71 pragma Inline (Send_Program_Error); 72 -- Raise Program_Error in the caller of the specified entry call 73 74 -------------------------- 75 -- Entry Calls Handling -- 76 -------------------------- 77 78 procedure Wakeup_Entry_Caller (Entry_Call : Entry_Call_Link); 79 pragma Inline (Wakeup_Entry_Caller); 80 -- This is called at the end of service of an entry call, to abort the 81 -- caller if he is in an abortable part, and to wake up the caller if he 82 -- is on Entry_Caller_Sleep. Call it holding the lock of Entry_Call.Self. 83 84 procedure Wait_For_Completion (Entry_Call : Entry_Call_Link); 85 pragma Inline (Wait_For_Completion); 86 -- This procedure suspends the calling task until the specified entry call 87 -- has either been completed or cancelled. On exit, the call will not be 88 -- queued. This waits for calls on protected entries. 89 -- Call this only when holding Self_ID locked. 90 91 procedure Check_Exception 92 (Self_ID : Task_Id; 93 Entry_Call : Entry_Call_Link); 94 pragma Inline (Check_Exception); 95 -- Raise any pending exception from the Entry_Call. This should be called 96 -- at the end of every compiler interface procedure that implements an 97 -- entry call. The caller should not be holding any locks, or there will 98 -- be deadlock. 99 100 procedure PO_Do_Or_Queue 101 (Object : Protection_Entry_Access; 102 Entry_Call : Entry_Call_Link); 103 -- This procedure executes or queues an entry call, depending on the status 104 -- of the corresponding barrier. The specified object is assumed locked. 105 106 --------------------- 107 -- Check_Exception -- 108 --------------------- 109 110 procedure Check_Exception 111 (Self_ID : Task_Id; 112 Entry_Call : Entry_Call_Link) 113 is 114 pragma Warnings (Off, Self_ID); 115 116 procedure Internal_Raise (X : Ada.Exceptions.Exception_Id); 117 pragma Import (C, Internal_Raise, "__gnat_raise_with_msg"); 118 119 use type Ada.Exceptions.Exception_Id; 120 121 E : constant Ada.Exceptions.Exception_Id := 122 Entry_Call.Exception_To_Raise; 123 124 begin 125 if E /= Ada.Exceptions.Null_Id then 126 Internal_Raise (E); 127 end if; 128 end Check_Exception; 129 130 ------------------------ 131 -- Send_Program_Error -- 132 ------------------------ 133 134 procedure Send_Program_Error (Entry_Call : Entry_Call_Link) is 135 Caller : constant Task_Id := Entry_Call.Self; 136 137 begin 138 Entry_Call.Exception_To_Raise := Program_Error'Identity; 139 STPO.Write_Lock (Caller); 140 Wakeup_Entry_Caller (Entry_Call); 141 STPO.Unlock (Caller); 142 end Send_Program_Error; 143 144 ------------------------- 145 -- Wait_For_Completion -- 146 ------------------------- 147 148 procedure Wait_For_Completion (Entry_Call : Entry_Call_Link) is 149 Self_Id : constant Task_Id := Entry_Call.Self; 150 begin 151 Self_Id.Common.State := Entry_Caller_Sleep; 152 STPO.Sleep (Self_Id, Entry_Caller_Sleep); 153 Self_Id.Common.State := Runnable; 154 end Wait_For_Completion; 155 156 ------------------------- 157 -- Wakeup_Entry_Caller -- 158 ------------------------- 159 160 -- This is called at the end of service of an entry call, to abort the 161 -- caller if he is in an abortable part, and to wake up the caller if it 162 -- is on Entry_Caller_Sleep. It assumes that the call is already off-queue. 163 164 -- (This enforces the rule that a task must be off-queue if its state is 165 -- Done or Cancelled.) Call it holding the lock of Entry_Call.Self. 166 167 -- The caller is waiting on Entry_Caller_Sleep, in Wait_For_Completion. 168 169 procedure Wakeup_Entry_Caller 170 (Entry_Call : Entry_Call_Link) 171 is 172 Caller : constant Task_Id := Entry_Call.Self; 173 begin 174 pragma Assert 175 (Caller.Common.State /= Terminated and then 176 Caller.Common.State /= Unactivated); 177 Entry_Call.State := Done; 178 STPO.Wakeup (Caller, Entry_Caller_Sleep); 179 end Wakeup_Entry_Caller; 180 181 ----------------------- 182 -- Restricted GNARLI -- 183 ----------------------- 184 185 -------------------------------------------- 186 -- Exceptional_Complete_Single_Entry_Body -- 187 -------------------------------------------- 188 189 procedure Exceptional_Complete_Single_Entry_Body 190 (Object : Protection_Entry_Access; 191 Ex : Ada.Exceptions.Exception_Id) 192 is 193 begin 194 Object.Call_In_Progress.Exception_To_Raise := Ex; 195 end Exceptional_Complete_Single_Entry_Body; 196 197 --------------------------------- 198 -- Initialize_Protection_Entry -- 199 --------------------------------- 200 201 procedure Initialize_Protection_Entry 202 (Object : Protection_Entry_Access; 203 Ceiling_Priority : Integer; 204 Compiler_Info : System.Address; 205 Entry_Body : Entry_Body_Access) 206 is 207 begin 208 Initialize_Protection (Object.Common'Access, Ceiling_Priority); 209 210 Object.Compiler_Info := Compiler_Info; 211 Object.Call_In_Progress := null; 212 Object.Entry_Body := Entry_Body; 213 Object.Entry_Queue := null; 214 end Initialize_Protection_Entry; 215 216 ---------------- 217 -- Lock_Entry -- 218 ---------------- 219 220 -- Compiler interface only 221 222 -- Do not call this procedure from within the run-time system. 223 224 procedure Lock_Entry (Object : Protection_Entry_Access) is 225 begin 226 Lock (Object.Common'Access); 227 end Lock_Entry; 228 229 -------------------------- 230 -- Lock_Read_Only_Entry -- 231 -------------------------- 232 233 -- Compiler interface only 234 235 -- Do not call this procedure from within the runtime system 236 237 procedure Lock_Read_Only_Entry (Object : Protection_Entry_Access) is 238 begin 239 Lock_Read_Only (Object.Common'Access); 240 end Lock_Read_Only_Entry; 241 242 -------------------- 243 -- PO_Do_Or_Queue -- 244 -------------------- 245 246 procedure PO_Do_Or_Queue 247 (Object : Protection_Entry_Access; 248 Entry_Call : Entry_Call_Link) 249 is 250 Barrier_Value : Boolean; 251 252 begin 253 -- When the Action procedure for an entry body returns, it must be 254 -- completed (having called [Exceptional_]Complete_Entry_Body). 255 256 Barrier_Value := Object.Entry_Body.Barrier (Object.Compiler_Info, 1); 257 258 if Barrier_Value then 259 if Object.Call_In_Progress /= null then 260 261 -- This violates the No_Entry_Queue restriction, send 262 -- Program_Error to the caller. 263 264 Send_Program_Error (Entry_Call); 265 return; 266 end if; 267 268 Object.Call_In_Progress := Entry_Call; 269 Object.Entry_Body.Action 270 (Object.Compiler_Info, Entry_Call.Uninterpreted_Data, 1); 271 Object.Call_In_Progress := null; 272 273 STPO.Write_Lock (Entry_Call.Self); 274 Wakeup_Entry_Caller (Entry_Call); 275 STPO.Unlock (Entry_Call.Self); 276 277 else 278 pragma Assert (Entry_Call.Mode = Simple_Call); 279 280 if Object.Entry_Queue /= null then 281 282 -- This violates the No_Entry_Queue restriction, send 283 -- Program_Error to the caller. 284 285 Send_Program_Error (Entry_Call); 286 return; 287 else 288 Object.Entry_Queue := Entry_Call; 289 end if; 290 291 end if; 292 293 exception 294 when others => 295 Send_Program_Error (Entry_Call); 296 end PO_Do_Or_Queue; 297 298 --------------------------- 299 -- Protected_Count_Entry -- 300 --------------------------- 301 302 function Protected_Count_Entry (Object : Protection_Entry) return Natural is 303 begin 304 if Object.Entry_Queue /= null then 305 return 1; 306 else 307 return 0; 308 end if; 309 end Protected_Count_Entry; 310 311 --------------------------------- 312 -- Protected_Single_Entry_Call -- 313 --------------------------------- 314 315 procedure Protected_Single_Entry_Call 316 (Object : Protection_Entry_Access; 317 Uninterpreted_Data : System.Address) 318 is 319 Self_Id : constant Task_Id := STPO.Self; 320 Entry_Call : Entry_Call_Record renames 321 Self_Id.Entry_Calls (Self_Id.Entry_Calls'First); 322 begin 323 -- If pragma Detect_Blocking is active then Program_Error must be 324 -- raised if this potentially blocking operation is called from a 325 -- protected action. 326 327 if Detect_Blocking 328 and then Self_Id.Common.Protected_Action_Nesting > 0 329 then 330 raise Program_Error with "potentially blocking operation"; 331 end if; 332 333 Lock_Entry (Object); 334 335 Entry_Call.Mode := Simple_Call; 336 Entry_Call.State := Now_Abortable; 337 Entry_Call.Uninterpreted_Data := Uninterpreted_Data; 338 Entry_Call.Exception_To_Raise := Ada.Exceptions.Null_Id; 339 340 PO_Do_Or_Queue (Object, Entry_Call'Access); 341 Unlock_Entry (Object); 342 343 -- The call is either `Done' or not. It cannot be cancelled since there 344 -- is no ATC construct. 345 346 pragma Assert (Entry_Call.State /= Cancelled); 347 348 if Entry_Call.State /= Done then 349 STPO.Write_Lock (Self_Id); 350 Wait_For_Completion (Entry_Call'Access); 351 STPO.Unlock (Self_Id); 352 end if; 353 354 Check_Exception (Self_Id, Entry_Call'Access); 355 end Protected_Single_Entry_Call; 356 357 ----------------------------------- 358 -- Protected_Single_Entry_Caller -- 359 ----------------------------------- 360 361 function Protected_Single_Entry_Caller 362 (Object : Protection_Entry) return Task_Id 363 is 364 begin 365 return Object.Call_In_Progress.Self; 366 end Protected_Single_Entry_Caller; 367 368 ------------------- 369 -- Service_Entry -- 370 ------------------- 371 372 procedure Service_Entry (Object : Protection_Entry_Access) is 373 Entry_Call : constant Entry_Call_Link := Object.Entry_Queue; 374 Caller : Task_Id; 375 376 begin 377 if Entry_Call /= null 378 and then Object.Entry_Body.Barrier (Object.Compiler_Info, 1) 379 then 380 Object.Entry_Queue := null; 381 382 if Object.Call_In_Progress /= null then 383 384 -- Violation of No_Entry_Queue restriction, raise exception 385 386 Send_Program_Error (Entry_Call); 387 Unlock_Entry (Object); 388 return; 389 end if; 390 391 Object.Call_In_Progress := Entry_Call; 392 Object.Entry_Body.Action 393 (Object.Compiler_Info, Entry_Call.Uninterpreted_Data, 1); 394 Object.Call_In_Progress := null; 395 Caller := Entry_Call.Self; 396 Unlock_Entry (Object); 397 398 STPO.Write_Lock (Caller); 399 Wakeup_Entry_Caller (Entry_Call); 400 STPO.Unlock (Caller); 401 402 else 403 -- Just unlock the entry 404 405 Unlock_Entry (Object); 406 end if; 407 408 exception 409 when others => 410 Send_Program_Error (Entry_Call); 411 Unlock_Entry (Object); 412 end Service_Entry; 413 414 ------------------ 415 -- Unlock_Entry -- 416 ------------------ 417 418 procedure Unlock_Entry (Object : Protection_Entry_Access) is 419 begin 420 Unlock (Object.Common'Access); 421 end Unlock_Entry; 422 423end System.Tasking.Protected_Objects.Single_Entry; 424