1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
5 -- SYSTEM.TASKING.PROTECTED_OBJECTS.ENTRIES --
9 -- Copyright (C) 1998-2010, Free Software Foundation, Inc. --
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. --
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. --
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/>. --
27 -- GNARL was developed by the GNARL team at Florida State University. --
28 -- Extensive contributions were provided by Ada Core Technologies, Inc. --
30 ------------------------------------------------------------------------------
32 -- This package contains all the simple primitives related to protected
33 -- objects with entries (i.e init, lock, unlock).
35 -- The handling of protected objects with no entries is done in
36 -- System.Tasking.Protected_Objects, the complex routines for protected
37 -- objects with entries in System.Tasking.Protected_Objects.Operations.
39 -- The split between Entries and Operations is needed to break circular
40 -- dependencies inside the run time.
42 -- Note: the compiler generates direct calls to this interface, via Rtsfind
44 with Ada.Unchecked_Deallocation;
46 with System.Task_Primitives.Operations;
47 with System.Restrictions;
48 with System.Parameters;
50 with System.Tasking.Initialization;
51 pragma Elaborate_All (System.Tasking.Initialization);
52 -- To insure that tasking is initialized if any protected objects are created
54 package body System.Tasking.Protected_Objects.Entries is
56 package STPO renames System.Task_Primitives.Operations;
59 use Task_Primitives.Operations;
61 -----------------------
62 -- Local Subprograms --
63 -----------------------
65 procedure Free_Entry_Names (Object : Protection_Entries);
66 -- Deallocate all string names associated with protected entries
72 Locking_Policy : Character;
73 pragma Import (C, Locking_Policy, "__gl_locking_policy");
79 overriding procedure Finalize (Object : in out Protection_Entries) is
80 Entry_Call : Entry_Call_Link;
82 Ceiling_Violation : Boolean;
83 Self_ID : constant Task_Id := STPO.Self;
84 Old_Base_Priority : System.Any_Priority;
87 if Object.Finalized then
91 STPO.Write_Lock (Object.L'Unrestricted_Access, Ceiling_Violation);
97 if Ceiling_Violation then
99 -- Dip our own priority down to ceiling of lock. See similar code in
100 -- Tasking.Entry_Calls.Lock_Server.
102 STPO.Write_Lock (Self_ID);
103 Old_Base_Priority := Self_ID.Common.Base_Priority;
104 Self_ID.New_Base_Priority := Object.Ceiling;
105 Initialization.Change_Base_Priority (Self_ID);
106 STPO.Unlock (Self_ID);
112 STPO.Write_Lock (Object.L'Unrestricted_Access, Ceiling_Violation);
114 if Ceiling_Violation then
115 raise Program_Error with "Ceiling Violation";
122 Object.Old_Base_Priority := Old_Base_Priority;
123 Object.Pending_Action := True;
126 -- Send program_error to all tasks still queued on this object
128 for E in Object.Entry_Queues'Range loop
129 Entry_Call := Object.Entry_Queues (E).Head;
131 while Entry_Call /= null loop
132 Caller := Entry_Call.Self;
133 Entry_Call.Exception_To_Raise := Program_Error'Identity;
135 STPO.Write_Lock (Caller);
136 Initialization.Wakeup_Entry_Caller (Self_ID, Entry_Call, Done);
137 STPO.Unlock (Caller);
139 exit when Entry_Call = Object.Entry_Queues (E).Tail;
140 Entry_Call := Entry_Call.Next;
144 Free_Entry_Names (Object);
146 Object.Finalized := True;
152 STPO.Unlock (Object.L'Unrestricted_Access);
154 STPO.Finalize_Lock (Object.L'Unrestricted_Access);
157 ----------------------
158 -- Free_Entry_Names --
159 ----------------------
161 procedure Free_Entry_Names (Object : Protection_Entries) is
162 Names : Entry_Names_Array_Access := Object.Entry_Names;
164 procedure Free_Entry_Names_Array_Access is new
165 Ada.Unchecked_Deallocation
166 (Entry_Names_Array, Entry_Names_Array_Access);
173 Free_Entry_Names_Array (Names.all);
174 Free_Entry_Names_Array_Access (Names);
175 end Free_Entry_Names;
182 (Object : Protection_Entries_Access) return System.Any_Priority is
184 return Object.New_Ceiling;
187 -------------------------------------
188 -- Has_Interrupt_Or_Attach_Handler --
189 -------------------------------------
191 function Has_Interrupt_Or_Attach_Handler
192 (Object : Protection_Entries_Access)
195 pragma Warnings (Off, Object);
198 end Has_Interrupt_Or_Attach_Handler;
200 -----------------------------------
201 -- Initialize_Protection_Entries --
202 -----------------------------------
204 procedure Initialize_Protection_Entries
205 (Object : Protection_Entries_Access;
206 Ceiling_Priority : Integer;
207 Compiler_Info : System.Address;
208 Entry_Bodies : Protected_Entry_Body_Access;
209 Find_Body_Index : Find_Body_Index_Access;
210 Build_Entry_Names : Boolean)
212 Init_Priority : Integer := Ceiling_Priority;
213 Self_ID : constant Task_Id := STPO.Self;
216 if Init_Priority = Unspecified_Priority then
217 Init_Priority := System.Priority'Last;
220 if Locking_Policy = 'C'
221 and then Has_Interrupt_Or_Attach_Handler (Object)
222 and then Init_Priority not in System.Interrupt_Priority
224 -- Required by C.3.1(11)
229 -- pragma Assert (Self_Id.Deferral_Level = 0);
230 -- If a PO is created from a controlled operation, abort is already
231 -- deferred at this point, so we need to use Defer_Abort_Nestable
232 -- In some cases, the above assertion can be useful to spot
233 -- inconsistencies, outside the above scenario involving controlled
236 Initialization.Defer_Abort_Nestable (Self_ID);
237 Initialize_Lock (Init_Priority, Object.L'Access);
238 Initialization.Undefer_Abort_Nestable (Self_ID);
240 Object.Ceiling := System.Any_Priority (Init_Priority);
241 Object.New_Ceiling := System.Any_Priority (Init_Priority);
242 Object.Owner := Null_Task;
243 Object.Compiler_Info := Compiler_Info;
244 Object.Pending_Action := False;
245 Object.Call_In_Progress := null;
246 Object.Entry_Bodies := Entry_Bodies;
247 Object.Find_Body_Index := Find_Body_Index;
249 for E in Object.Entry_Queues'Range loop
250 Object.Entry_Queues (E).Head := null;
251 Object.Entry_Queues (E).Tail := null;
254 if Build_Entry_Names then
255 Object.Entry_Names :=
256 new Entry_Names_Array (1 .. Entry_Index (Object.Num_Entries));
258 end Initialize_Protection_Entries;
264 procedure Lock_Entries
265 (Object : Protection_Entries_Access;
266 Ceiling_Violation : out Boolean)
269 if Object.Finalized then
270 raise Program_Error with "Protected Object is finalized";
273 -- If pragma Detect_Blocking is active then, as described in the ARM
274 -- 9.5.1, par. 15, we must check whether this is an external call on a
275 -- protected subprogram with the same target object as that of the
276 -- protected action that is currently in progress (i.e., if the caller
277 -- is already the protected object's owner). If this is the case hence
278 -- Program_Error must be raised.
280 if Detect_Blocking and then Object.Owner = Self then
284 -- The lock is made without deferring abort
286 -- Therefore the abort has to be deferred before calling this routine.
287 -- This means that the compiler has to generate a Defer_Abort call
288 -- before the call to Lock.
290 -- The caller is responsible for undeferring abort, and compiler
291 -- generated calls must be protected with cleanup handlers to ensure
292 -- that abort is undeferred in all cases.
295 (STPO.Self.Deferral_Level > 0
296 or else not Restrictions.Abort_Allowed);
298 Write_Lock (Object.L'Access, Ceiling_Violation);
300 -- We are entering in a protected action, so that we increase the
301 -- protected object nesting level (if pragma Detect_Blocking is
302 -- active), and update the protected object's owner.
304 if Detect_Blocking then
306 Self_Id : constant Task_Id := Self;
309 -- Update the protected object's owner
311 Object.Owner := Self_Id;
313 -- Increase protected object nesting level
315 Self_Id.Common.Protected_Action_Nesting :=
316 Self_Id.Common.Protected_Action_Nesting + 1;
322 procedure Lock_Entries (Object : Protection_Entries_Access) is
323 Ceiling_Violation : Boolean;
326 Lock_Entries (Object, Ceiling_Violation);
328 if Ceiling_Violation then
329 raise Program_Error with "Ceiling Violation";
333 ----------------------------
334 -- Lock_Read_Only_Entries --
335 ----------------------------
337 procedure Lock_Read_Only_Entries (Object : Protection_Entries_Access) is
338 Ceiling_Violation : Boolean;
341 if Object.Finalized then
342 raise Program_Error with "Protected Object is finalized";
345 -- If pragma Detect_Blocking is active then, as described in the ARM
346 -- 9.5.1, par. 15, we must check whether this is an external call on a
347 -- protected subprogram with the same target object as that of the
348 -- protected action that is currently in progress (i.e., if the caller
349 -- is already the protected object's owner). If this is the case hence
350 -- Program_Error must be raised.
352 -- Note that in this case (getting read access), several tasks may
353 -- have read ownership of the protected object, so that this method of
354 -- storing the (single) protected object's owner does not work
355 -- reliably for read locks. However, this is the approach taken for two
356 -- major reasons: first, this function is not currently being used (it
357 -- is provided for possible future use), and second, it largely
358 -- simplifies the implementation.
360 if Detect_Blocking and then Object.Owner = Self then
364 Read_Lock (Object.L'Access, Ceiling_Violation);
366 if Ceiling_Violation then
367 raise Program_Error with "Ceiling Violation";
370 -- We are entering in a protected action, so that we increase the
371 -- protected object nesting level (if pragma Detect_Blocking is
372 -- active), and update the protected object's owner.
374 if Detect_Blocking then
376 Self_Id : constant Task_Id := Self;
379 -- Update the protected object's owner
381 Object.Owner := Self_Id;
383 -- Increase protected object nesting level
385 Self_Id.Common.Protected_Action_Nesting :=
386 Self_Id.Common.Protected_Action_Nesting + 1;
389 end Lock_Read_Only_Entries;
395 procedure Set_Ceiling
396 (Object : Protection_Entries_Access;
397 Prio : System.Any_Priority) is
399 Object.New_Ceiling := Prio;
406 procedure Set_Entry_Name
407 (Object : Protection_Entries'Class;
408 Pos : Protected_Entry_Index;
412 pragma Assert (Object.Entry_Names /= null);
414 Object.Entry_Names (Entry_Index (Pos)) := Val;
421 procedure Unlock_Entries (Object : Protection_Entries_Access) is
423 -- We are exiting from a protected action, so that we decrease the
424 -- protected object nesting level (if pragma Detect_Blocking is
425 -- active), and remove ownership of the protected object.
427 if Detect_Blocking then
429 Self_Id : constant Task_Id := Self;
432 -- Calls to this procedure can only take place when being within
433 -- a protected action and when the caller is the protected
436 pragma Assert (Self_Id.Common.Protected_Action_Nesting > 0
437 and then Object.Owner = Self_Id);
439 -- Remove ownership of the protected object
441 Object.Owner := Null_Task;
443 Self_Id.Common.Protected_Action_Nesting :=
444 Self_Id.Common.Protected_Action_Nesting - 1;
448 -- Before releasing the mutex we must actually update its ceiling
449 -- priority if it has been changed.
451 if Object.New_Ceiling /= Object.Ceiling then
452 if Locking_Policy = 'C' then
453 System.Task_Primitives.Operations.Set_Ceiling
454 (Object.L'Access, Object.New_Ceiling);
457 Object.Ceiling := Object.New_Ceiling;
460 Unlock (Object.L'Access);
463 end System.Tasking.Protected_Objects.Entries;