1 ------------------------------------------------------------------------------
3 -- GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS --
5 -- SYSTEM.TASKING.PROTECTED_OBJECTS.SINGLE_ENTRY --
11 -- Copyright (C) 1991-2001 Florida State University --
13 -- GNARL is free software; you can redistribute it and/or modify it under --
14 -- terms of the GNU General Public License as published by the Free Soft- --
15 -- ware Foundation; either version 2, or (at your option) any later ver- --
16 -- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
17 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
18 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
19 -- for more details. You should have received a copy of the GNU General --
20 -- Public License distributed with GNARL; see file COPYING. If not, write --
21 -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
22 -- MA 02111-1307, USA. --
24 -- As a special exception, if other files instantiate generics from this --
25 -- unit, or you link this unit with other files to produce an executable, --
26 -- this unit does not by itself cause the resulting executable to be --
27 -- covered by the GNU General Public License. This exception does not --
28 -- however invalidate any other reasons why the executable file might be --
29 -- covered by the GNU Public License. --
31 -- GNARL was developed by the GNARL team at Florida State University. It is --
32 -- now maintained by Ada Core Technologies Inc. in cooperation with Florida --
33 -- State University (http://www.gnat.com). --
35 ------------------------------------------------------------------------------
37 -- This package provides an optimized version of Protected_Objects.Operations
38 -- and Protected_Objects.Entries making the following assumptions:
40 -- PO have only one entry
41 -- There is only one caller at a time (No_Entry_Queue)
42 -- There is no dynamic priority support (No_Dynamic_Priorities)
43 -- No Abort Statements
44 -- (No_Abort_Statements, Max_Asynchronous_Select_Nesting => 0)
45 -- PO are at library level
46 -- None of the tasks will terminate (no need for finalization)
48 -- This interface is intended to be used in the ravenscar profile, the
49 -- compiler is responsible for ensuring that the conditions mentioned above
50 -- are respected, except for the No_Entry_Queue restriction that is checked
51 -- dynamically in this package, since the check cannot be performed at compile
52 -- time, and is relatively cheap (see body).
54 -- This package is part of the high level tasking interface used by the
55 -- compiler to expand Ada 95 tasking constructs into simpler run time calls
56 -- (aka GNARLI, GNU Ada Run-time Library Interface)
58 -- Note: the compiler generates direct calls to this interface, via Rtsfind.
59 -- Any changes to this interface may require corresponding compiler changes
60 -- in exp_ch9.adb and possibly exp_ch7.adb
62 package System.Tasking.Protected_Objects.Single_Entry is
63 pragma Elaborate_Body;
65 ---------------------------------
66 -- Compiler Interface (GNARLI) --
67 ---------------------------------
69 -- The compiler will expand in the GNAT tree the following construct:
75 -- Open : Boolean := False;
78 -- protected body PO is
79 -- entry E when Open is
80 -- ...variable declarations...
86 -- ...variable declarations...
94 -- protected type poT is
98 -- open : boolean := false;
100 -- type poTV is limited record
101 -- open : boolean := false;
102 -- _object : aliased protection_entry;
104 -- procedure poPT__E1s (O : address; P : address; E :
105 -- protected_entry_index);
106 -- function poPT__B2s (O : address; E : protected_entry_index) return
108 -- procedure poPT__pN (_object : in out poTV);
109 -- procedure poPT__pP (_object : in out poTV);
110 -- poTA : aliased entry_body := (
111 -- barrier => poPT__B2s'unrestricted_access,
112 -- action => poPT__E1s'unrestricted_access);
114 -- procedure _init_proc (_init : in out poTV) is
116 -- _init.open := false;
117 -- _init_proc (_init._object);
118 -- initialize_protection_entry (_init._object'unchecked_access,
119 -- unspecified_priority, _init'address, poTA'
120 -- unrestricted_access);
125 -- _init_proc (poTV!(po));
127 -- function poPT__B2s (O : address; E : protected_entry_index) return
129 -- type poTVP is access poTV;
130 -- _object : poTVP := poTVP!(O);
131 -- poR : protection_entry renames _object._object;
132 -- openP : boolean renames _object.open;
137 -- procedure poPT__E1s (O : address; P : address; E :
138 -- protected_entry_index) is
139 -- type poTVP is access poTV;
140 -- _object : poTVP := poTVP!(O);
143 -- poR : protection_entry renames _object._object;
144 -- openP : boolean renames _object.open;
145 -- ...variable declarations...
149 -- complete_single_entry_body (_object._object'unchecked_access);
152 -- when all others =>
153 -- exceptional_complete_single_entry_body (_object._object'
154 -- unchecked_access, get_gnat_exception);
158 -- procedure poPT__pN (_object : in out poTV) is
159 -- poR : protection_entry renames _object._object;
160 -- openP : boolean renames _object.open;
161 -- ...variable declarations...
167 -- procedure poPT__pP (_object : in out poTV) is
168 -- procedure _clean is
170 -- service_entry (_object._object'unchecked_access);
171 -- unlock_entry (_object._object'unchecked_access);
175 -- lock_entry (_object._object'unchecked_access);
177 -- poPT__pN (_object);
184 type Protection_Entry is limited private;
185 -- This type contains the GNARL state of a protected object. The
186 -- application-defined portion of the state (i.e. private objects)
187 -- is maintained by the compiler-generated code.
189 type Protection_Entry_Access is access all Protection_Entry;
191 procedure Initialize_Protection_Entry
192 (Object : Protection_Entry_Access;
193 Ceiling_Priority : Integer;
194 Compiler_Info : System.Address;
195 Entry_Body : Entry_Body_Access);
196 -- Initialize the Object parameter so that it can be used by the run time
197 -- to keep track of the runtime state of a protected object.
199 procedure Lock_Entry (Object : Protection_Entry_Access);
200 -- Lock a protected object for write access. Upon return, the caller
201 -- owns the lock to this object, and no other call to Lock or
202 -- Lock_Read_Only with the same argument will return until the
203 -- corresponding call to Unlock has been made by the caller.
205 procedure Lock_Read_Only_Entry
206 (Object : Protection_Entry_Access);
207 -- Lock a protected object for read access. Upon return, the caller
208 -- owns the lock for read access, and no other calls to Lock
209 -- with the same argument will return until the corresponding call
210 -- to Unlock has been made by the caller. Other cals to Lock_Read_Only
211 -- may (but need not) return before the call to Unlock, and the
212 -- corresponding callers will also own the lock for read access.
214 procedure Unlock_Entry (Object : Protection_Entry_Access);
215 -- Relinquish ownership of the lock for the object represented by
216 -- the Object parameter. If this ownership was for write access, or
217 -- if it was for read access where there are no other read access
218 -- locks outstanding, one (or more, in the case of Lock_Read_Only)
219 -- of the tasks waiting on this lock (if any) will be given the
220 -- lock and allowed to return from the Lock or Lock_Read_Only call.
222 procedure Service_Entry (Object : Protection_Entry_Access);
223 -- Service the entry queue of the specified object, executing the
224 -- corresponding body of any queued entry call that is waiting on True
225 -- barrier. This is used when the state of a protected object may have
226 -- changed, in particular after the execution of the statement sequence of
227 -- a protected procedure.
228 -- This must be called with abortion deferred and with the corresponding
231 procedure Protected_Single_Entry_Call
232 (Object : Protection_Entry_Access;
233 Uninterpreted_Data : System.Address;
235 -- Make a protected entry call to the specified object.
236 -- Pend a protected entry call on the protected object represented
237 -- by Object. A pended call is not queued; it may be executed immediately
238 -- or queued, depending on the state of the entry barrier.
240 -- Uninterpreted_Data
241 -- This will be returned by Next_Entry_Call when this call is serviced.
242 -- It can be used by the compiler to pass information between the
243 -- caller and the server, in particular entry parameters.
246 -- The kind of call to be pended
248 procedure Timed_Protected_Single_Entry_Call
249 (Object : Protection_Entry_Access;
250 Uninterpreted_Data : System.Address;
253 Entry_Call_Successful : out Boolean);
254 -- Same as the Protected_Entry_Call but with time-out specified.
255 -- This routine is used to implement timed entry calls.
257 procedure Complete_Single_Entry_Body
258 (Object : Protection_Entry_Access);
259 pragma Inline (Complete_Single_Entry_Body);
260 -- Called from within an entry body procedure, indicates that the
261 -- corresponding entry call has been serviced.
263 procedure Exceptional_Complete_Single_Entry_Body
264 (Object : Protection_Entry_Access;
265 Ex : Ada.Exceptions.Exception_Id);
266 -- Perform all of the functions of Complete_Entry_Body. In addition,
267 -- report in Ex the exception whose propagation terminated the entry
268 -- body to the runtime system.
270 function Protected_Count_Entry (Object : Protection_Entry)
272 -- Return the number of entry calls on Object (0 or 1).
274 function Protected_Single_Entry_Caller (Object : Protection_Entry)
276 -- Return value of E'Caller, where E is the protected entry currently
277 -- being handled. This will only work if called from within an
278 -- entry body, as required by the LRM (C.7.1(14)).
281 type Protection_Entry is record
282 L : aliased Task_Primitives.Lock;
283 Compiler_Info : System.Address;
284 Call_In_Progress : Entry_Call_Link;
285 Ceiling : System.Any_Priority;
286 Entry_Body : Entry_Body_Access;
287 Entry_Queue : Entry_Call_Link;
289 pragma Volatile (Protection_Entry);
290 for Protection_Entry'Alignment use Standard'Maximum_Alignment;
291 -- Use maximum alignement so that one can convert a protection_entry_access
294 end System.Tasking.Protected_Objects.Single_Entry;