1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
5 -- S Y S T E M . T A S K I N G . P R O T E C T E D _ O B J E C T S . --
10 -- Copyright (C) 1998-2007, Free Software Foundation, Inc. --
12 -- GNARL is free software; you can redistribute it and/or modify it under --
13 -- terms of the GNU General Public License as published by the Free Soft- --
14 -- ware Foundation; either version 2, or (at your option) any later ver- --
15 -- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
16 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
17 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
18 -- for more details. You should have received a copy of the GNU General --
19 -- Public License distributed with GNARL; see file COPYING. If not, write --
20 -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
21 -- Boston, MA 02110-1301, USA. --
23 -- As a special exception, if other files instantiate generics from this --
24 -- unit, or you link this unit with other files to produce an executable, --
25 -- this unit does not by itself cause the resulting executable to be --
26 -- covered by the GNU General Public License. This exception does not --
27 -- however invalidate any other reasons why the executable file might be --
28 -- covered by the GNU Public License. --
30 -- GNARL was developed by the GNARL team at Florida State University. --
31 -- Extensive contributions were provided by Ada Core Technologies, Inc. --
33 ------------------------------------------------------------------------------
35 -- This package contains all the simple primitives related to protected
36 -- objects with entries (i.e init, lock, unlock).
38 -- The handling of protected objects with no entries is done in
39 -- System.Tasking.Protected_Objects, the complex routines for protected
40 -- objects with entries in System.Tasking.Protected_Objects.Operations.
42 -- The split between Entries and Operations is needed to break circular
43 -- dependencies inside the run time.
45 -- Note: the compiler generates direct calls to this interface, via Rtsfind
48 -- Used for Exception_Occurrence_Access
51 with System.Task_Primitives.Operations;
52 -- Used for Initialize_Lock
59 with System.Tasking.Initialization;
60 -- Used for Defer_Abort,
62 -- Change_Base_Priority
64 pragma Elaborate_All (System.Tasking.Initialization);
65 -- This insures that tasking is initialized if any protected objects are
68 with System.Restrictions;
69 -- Used for Abort_Allowed
71 with System.Parameters;
72 -- Used for Single_Lock
74 package body System.Tasking.Protected_Objects.Entries is
76 package STPO renames System.Task_Primitives.Operations;
79 use Task_Primitives.Operations;
86 Locking_Policy : Character;
87 pragma Import (C, Locking_Policy, "__gl_locking_policy");
93 procedure Finalize (Object : in out Protection_Entries) is
94 Entry_Call : Entry_Call_Link;
96 Ceiling_Violation : Boolean;
97 Self_ID : constant Task_Id := STPO.Self;
98 Old_Base_Priority : System.Any_Priority;
101 if Object.Finalized then
105 STPO.Write_Lock (Object.L'Unrestricted_Access, Ceiling_Violation);
111 if Ceiling_Violation then
113 -- Dip our own priority down to ceiling of lock. See similar code in
114 -- Tasking.Entry_Calls.Lock_Server.
116 STPO.Write_Lock (Self_ID);
117 Old_Base_Priority := Self_ID.Common.Base_Priority;
118 Self_ID.New_Base_Priority := Object.Ceiling;
119 Initialization.Change_Base_Priority (Self_ID);
120 STPO.Unlock (Self_ID);
126 STPO.Write_Lock (Object.L'Unrestricted_Access, Ceiling_Violation);
128 if Ceiling_Violation then
129 Raise_Exception (Program_Error'Identity, "Ceiling Violation");
136 Object.Old_Base_Priority := Old_Base_Priority;
137 Object.Pending_Action := True;
140 -- Send program_error to all tasks still queued on this object
142 for E in Object.Entry_Queues'Range loop
143 Entry_Call := Object.Entry_Queues (E).Head;
145 while Entry_Call /= null loop
146 Caller := Entry_Call.Self;
147 Entry_Call.Exception_To_Raise := Program_Error'Identity;
149 STPO.Write_Lock (Caller);
150 Initialization.Wakeup_Entry_Caller (Self_ID, Entry_Call, Done);
151 STPO.Unlock (Caller);
153 exit when Entry_Call = Object.Entry_Queues (E).Tail;
154 Entry_Call := Entry_Call.Next;
158 Object.Finalized := True;
164 STPO.Unlock (Object.L'Unrestricted_Access);
166 STPO.Finalize_Lock (Object.L'Unrestricted_Access);
174 (Object : Protection_Entries_Access) return System.Any_Priority is
176 return Object.New_Ceiling;
179 -------------------------------------
180 -- Has_Interrupt_Or_Attach_Handler --
181 -------------------------------------
183 function Has_Interrupt_Or_Attach_Handler
184 (Object : Protection_Entries_Access)
187 pragma Warnings (Off, Object);
190 end Has_Interrupt_Or_Attach_Handler;
192 -----------------------------------
193 -- Initialize_Protection_Entries --
194 -----------------------------------
196 procedure Initialize_Protection_Entries
197 (Object : Protection_Entries_Access;
198 Ceiling_Priority : Integer;
199 Compiler_Info : System.Address;
200 Entry_Bodies : Protected_Entry_Body_Access;
201 Find_Body_Index : Find_Body_Index_Access)
203 Init_Priority : Integer := Ceiling_Priority;
204 Self_ID : constant Task_Id := STPO.Self;
207 if Init_Priority = Unspecified_Priority then
208 Init_Priority := System.Priority'Last;
211 if Locking_Policy = 'C'
212 and then Has_Interrupt_Or_Attach_Handler (Object)
213 and then Init_Priority not in System.Interrupt_Priority
215 -- Required by C.3.1(11)
220 Initialization.Defer_Abort (Self_ID);
221 Initialize_Lock (Init_Priority, Object.L'Access);
222 Initialization.Undefer_Abort (Self_ID);
224 Object.Ceiling := System.Any_Priority (Init_Priority);
225 Object.New_Ceiling := System.Any_Priority (Init_Priority);
226 Object.Owner := Null_Task;
227 Object.Compiler_Info := Compiler_Info;
228 Object.Pending_Action := False;
229 Object.Call_In_Progress := null;
230 Object.Entry_Bodies := Entry_Bodies;
231 Object.Find_Body_Index := Find_Body_Index;
233 for E in Object.Entry_Queues'Range loop
234 Object.Entry_Queues (E).Head := null;
235 Object.Entry_Queues (E).Tail := null;
237 end Initialize_Protection_Entries;
243 procedure Lock_Entries
244 (Object : Protection_Entries_Access;
245 Ceiling_Violation : out Boolean)
248 if Object.Finalized then
250 (Program_Error'Identity, "Protected Object is finalized");
253 -- If pragma Detect_Blocking is active then, as described in the ARM
254 -- 9.5.1, par. 15, we must check whether this is an external call on a
255 -- protected subprogram with the same target object as that of the
256 -- protected action that is currently in progress (i.e., if the caller
257 -- is already the protected object's owner). If this is the case hence
258 -- Program_Error must be raised.
260 if Detect_Blocking and then Object.Owner = Self then
264 -- The lock is made without defering abort
266 -- Therefore the abort has to be deferred before calling this routine.
267 -- This means that the compiler has to generate a Defer_Abort call
268 -- before the call to Lock.
270 -- The caller is responsible for undeferring abort, and compiler
271 -- generated calls must be protected with cleanup handlers to ensure
272 -- that abort is undeferred in all cases.
275 (STPO.Self.Deferral_Level > 0
276 or else not Restrictions.Abort_Allowed);
278 Write_Lock (Object.L'Access, Ceiling_Violation);
280 -- We are entering in a protected action, so that we increase the
281 -- protected object nesting level (if pragma Detect_Blocking is
282 -- active), and update the protected object's owner.
284 if Detect_Blocking then
286 Self_Id : constant Task_Id := Self;
289 -- Update the protected object's owner
291 Object.Owner := Self_Id;
293 -- Increase protected object nesting level
295 Self_Id.Common.Protected_Action_Nesting :=
296 Self_Id.Common.Protected_Action_Nesting + 1;
302 procedure Lock_Entries (Object : Protection_Entries_Access) is
303 Ceiling_Violation : Boolean;
306 Lock_Entries (Object, Ceiling_Violation);
308 if Ceiling_Violation then
309 Raise_Exception (Program_Error'Identity, "Ceiling Violation");
313 ----------------------------
314 -- Lock_Read_Only_Entries --
315 ----------------------------
317 procedure Lock_Read_Only_Entries (Object : Protection_Entries_Access) is
318 Ceiling_Violation : Boolean;
321 if Object.Finalized then
323 (Program_Error'Identity, "Protected Object is finalized");
326 -- If pragma Detect_Blocking is active then, as described in the ARM
327 -- 9.5.1, par. 15, we must check whether this is an external call on a
328 -- protected subprogram with the same target object as that of the
329 -- protected action that is currently in progress (i.e., if the caller
330 -- is already the protected object's owner). If this is the case hence
331 -- Program_Error must be raised.
333 -- Note that in this case (getting read access), several tasks may
334 -- have read ownership of the protected object, so that this method of
335 -- storing the (single) protected object's owner does not work
336 -- reliably for read locks. However, this is the approach taken for two
337 -- major reasosn: first, this function is not currently being used (it
338 -- is provided for possible future use), and second, it largely
339 -- simplifies the implementation.
341 if Detect_Blocking and then Object.Owner = Self then
345 Read_Lock (Object.L'Access, Ceiling_Violation);
347 if Ceiling_Violation then
348 Raise_Exception (Program_Error'Identity, "Ceiling Violation");
351 -- We are entering in a protected action, so that we increase the
352 -- protected object nesting level (if pragma Detect_Blocking is
353 -- active), and update the protected object's owner.
355 if Detect_Blocking then
357 Self_Id : constant Task_Id := Self;
360 -- Update the protected object's owner
362 Object.Owner := Self_Id;
364 -- Increase protected object nesting level
366 Self_Id.Common.Protected_Action_Nesting :=
367 Self_Id.Common.Protected_Action_Nesting + 1;
370 end Lock_Read_Only_Entries;
376 procedure Set_Ceiling
377 (Object : Protection_Entries_Access;
378 Prio : System.Any_Priority) is
380 Object.New_Ceiling := Prio;
387 procedure Unlock_Entries (Object : Protection_Entries_Access) is
389 -- We are exiting from a protected action, so that we decrease the
390 -- protected object nesting level (if pragma Detect_Blocking is
391 -- active), and remove ownership of the protected object.
393 if Detect_Blocking then
395 Self_Id : constant Task_Id := Self;
398 -- Calls to this procedure can only take place when being within
399 -- a protected action and when the caller is the protected
402 pragma Assert (Self_Id.Common.Protected_Action_Nesting > 0
403 and then Object.Owner = Self_Id);
405 -- Remove ownership of the protected object
407 Object.Owner := Null_Task;
409 Self_Id.Common.Protected_Action_Nesting :=
410 Self_Id.Common.Protected_Action_Nesting - 1;
414 -- Before releasing the mutex we must actually update its ceiling
415 -- priority if it has been changed.
417 if Object.New_Ceiling /= Object.Ceiling then
418 if Locking_Policy = 'C' then
419 System.Task_Primitives.Operations.Set_Ceiling
420 (Object.L'Access, Object.New_Ceiling);
423 Object.Ceiling := Object.New_Ceiling;
426 Unlock (Object.L'Access);
429 end System.Tasking.Protected_Objects.Entries;