File : s-tposen.ads
1 ------------------------------------------------------------------------------
2 -- --
3 -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
4 -- --
5 -- SYSTEM.TASKING.PROTECTED_OBJECTS.SINGLE_ENTRY --
6 -- --
7 -- S p e c --
8 -- --
9 -- Copyright (C) 1992-2013, Free Software Foundation, Inc. --
10 -- --
11 -- GNAT 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 -- --
19 -- --
20 -- --
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 provides an optimized version of Protected_Objects.Operations
33 -- and Protected_Objects.Entries making the following assumptions:
34
35 -- PO have only one entry
36 -- There is only one caller at a time (No_Entry_Queue)
37 -- There is no dynamic priority support (No_Dynamic_Priorities)
38 -- No Abort Statements
39 -- (No_Abort_Statements, Max_Asynchronous_Select_Nesting => 0)
40 -- PO are at library level
41 -- None of the tasks will terminate (no need for finalization)
42
43 -- This interface is intended to be used in the Ravenscar profile, the
44 -- compiler is responsible for ensuring that the conditions mentioned above
45 -- are respected, except for the No_Entry_Queue restriction that is checked
46 -- dynamically in this package, since the check cannot be performed at compile
47 -- time, and is relatively cheap (see body).
48
49 -- This package is part of the high level tasking interface used by the
50 -- compiler to expand Ada 95 tasking constructs into simpler run time calls
51 -- (aka GNARLI, GNU Ada Run-time Library Interface)
52
53 -- Note: the compiler generates direct calls to this interface, via Rtsfind.
54 -- Any changes to this interface may require corresponding compiler changes
55 -- in exp_ch9.adb and possibly exp_ch7.adb
56
57 package System.Tasking.Protected_Objects.Single_Entry is
58 pragma Elaborate_Body;
59
60 ---------------------------------
61 -- Compiler Interface (GNARLI) --
62 ---------------------------------
63
64 -- The compiler will expand in the GNAT tree the following construct:
65
66 -- protected PO is
67 -- entry E;
68 -- procedure P;
69 -- private
70 -- Open : Boolean := False;
71 -- end PO;
72
73 -- protected body PO is
74 -- entry E when Open is
75 -- ...variable declarations...
76 -- begin
77 -- ...B...
78 -- end E;
79
80 -- procedure P is
81 -- ...variable declarations...
82 -- begin
83 -- ...C...
84 -- end P;
85 -- end PO;
86
87 -- as follows:
88
89 -- protected type poT is
90 -- entry e;
91 -- procedure p;
92 -- private
93 -- open : boolean := false;
94 -- end poT;
95 -- type poTV is limited record
96 -- open : boolean := false;
97 -- _object : aliased protection_entry;
98 -- end record;
99 -- procedure poPT__E1s (O : address; P : address; E :
100 -- protected_entry_index);
101 -- function poPT__B2s (O : address; E : protected_entry_index) return
102 -- boolean;
103 -- procedure poPT__pN (_object : in out poTV);
104 -- procedure poPT__pP (_object : in out poTV);
105 -- poTA : aliased entry_body := (
106 -- barrier => poPT__B2s'unrestricted_access,
107 -- action => poPT__E1s'unrestricted_access);
108 -- freeze poTV [
109 -- procedure poTVIP (_init : in out poTV) is
110 -- begin
111 -- _init.open := false;
112 -- object-init-proc (_init._object);
113 -- initialize_protection_entry (_init._object'unchecked_access,
114 -- unspecified_priority, _init'address, poTA'
115 -- unrestricted_access);
116 -- return;
117 -- end poTVIP;
118 -- ]
119 -- po : poT;
120 -- poTVIP (poTV!(po));
121
122 -- function poPT__B2s (O : address; E : protected_entry_index) return
123 -- boolean is
124 -- type poTVP is access poTV;
125 -- _object : poTVP := poTVP!(O);
126 -- poR : protection_entry renames _object._object;
127 -- openP : boolean renames _object.open;
128 -- begin
129 -- return open;
130 -- end poPT__B2s;
131
132 -- procedure poPT__E1s (O : address; P : address; E :
133 -- protected_entry_index) is
134 -- type poTVP is access poTV;
135 -- _object : poTVP := poTVP!(O);
136 -- begin
137 -- B1b : declare
138 -- poR : protection_entry renames _object._object;
139 -- openP : boolean renames _object.open;
140 -- ...variable declarations...
141 -- begin
142 -- ...B...
143 -- end B1b;
144 -- complete_single_entry_body (_object._object'unchecked_access);
145 -- return;
146 -- exception
147 -- when all others =>
148 -- exceptional_complete_single_entry_body (_object._object'
149 -- unchecked_access, get_gnat_exception);
150 -- return;
151 -- end poPT__E1s;
152
153 -- procedure poPT__pN (_object : in out poTV) is
154 -- poR : protection_entry renames _object._object;
155 -- openP : boolean renames _object.open;
156 -- ...variable declarations...
157 -- begin
158 -- ...C...
159 -- return;
160 -- end poPT__pN;
161
162 -- procedure poPT__pP (_object : in out poTV) is
163 -- procedure _clean is
164 -- begin
165 -- service_entry (_object._object'unchecked_access);
166 -- return;
167 -- end _clean;
168 -- begin
169 -- lock_entry (_object._object'unchecked_access);
170 -- B5b : begin
171 -- poPT__pN (_object);
172 -- at end
173 -- _clean;
174 -- end B5b;
175 -- return;
176 -- end poPT__pP;
177
178 type Protection_Entry is limited private;
179 -- This type contains the GNARL state of a protected object. The
180 -- application-defined portion of the state (i.e. private objects)
181 -- is maintained by the compiler-generated code.
182
183 type Protection_Entry_Access is access all Protection_Entry;
184
185 procedure Initialize_Protection_Entry
186 (Object : Protection_Entry_Access;
187 Ceiling_Priority : Integer;
188 Compiler_Info : System.Address;
189 Entry_Body : Entry_Body_Access);
190 -- Initialize the Object parameter so that it can be used by the run time
191 -- to keep track of the runtime state of a protected object.
192
193 procedure Lock_Entry (Object : Protection_Entry_Access);
194 -- Lock a protected object for write access. Upon return, the caller owns
195 -- the lock to this object, and no other call to Lock or Lock_Read_Only
196 -- with the same argument will return until the corresponding call to
197 -- Unlock has been made by the caller.
198
199 procedure Lock_Read_Only_Entry
200 (Object : Protection_Entry_Access);
201 -- Lock a protected object for read access. Upon return, the caller owns
202 -- the lock for read access, and no other calls to Lock with the same
203 -- argument will return until the corresponding call to Unlock has been
204 -- made by the caller. Other calls to Lock_Read_Only may (but need not)
205 -- return before the call to Unlock, and the corresponding callers will
206 -- also own the lock for read access.
207
208 procedure Unlock_Entry (Object : Protection_Entry_Access);
209 -- Relinquish ownership of the lock for the object represented by the
210 -- Object parameter. If this ownership was for write access, or if it was
211 -- for read access where there are no other read access locks outstanding,
212 -- one (or more, in the case of Lock_Read_Only) of the tasks waiting on
213 -- this lock (if any) will be given the lock and allowed to return from
214 -- the Lock or Lock_Read_Only call.
215
216 procedure Service_Entry (Object : Protection_Entry_Access);
217 -- Service the entry queue of the specified object, executing the
218 -- corresponding body of any queued entry call that is waiting on True
219 -- barrier. This is used when the state of a protected object may have
220 -- changed, in particular after the execution of the statement sequence
221 -- of a protected procedure.
222 --
223 -- This must be called with abort deferred and with the corresponding
224 -- object locked. Object is unlocked on return.
225
226 procedure Protected_Single_Entry_Call
227 (Object : Protection_Entry_Access;
228 Uninterpreted_Data : System.Address);
229 -- Make a protected entry call to the specified object
230 --
231 -- Pends a protected entry call on the protected object represented by
232 -- Object. A pended call is not queued; it may be executed immediately
233 -- or queued, depending on the state of the entry barrier.
234 --
235 -- Uninterpreted_Data
236 -- This will be returned by Next_Entry_Call when this call is serviced.
237 -- It can be used by the compiler to pass information between the
238 -- caller and the server, in particular entry parameters.
239
240 procedure Exceptional_Complete_Single_Entry_Body
241 (Object : Protection_Entry_Access;
242 Ex : Ada.Exceptions.Exception_Id);
243 -- Perform all of the functions of Complete_Entry_Body. In addition, report
244 -- in Ex the exception whose propagation terminated the entry body to the
245 -- runtime system.
246
247 function Protected_Count_Entry (Object : Protection_Entry) return Natural;
248 -- Return the number of entry calls on Object (0 or 1)
249
250 function Protected_Single_Entry_Caller
251 (Object : Protection_Entry) return Task_Id;
252 -- Return value of E'Caller, where E is the protected entry currently being
253 -- handled. This will only work if called from within an entry body, as
254 -- required by the LRM (C.7.1(14)).
255
256 private
257 type Protection_Entry is record
258 Common : aliased Protection;
259 -- State of the protected object. This part is common to any protected
260 -- object, including those without entries.
261
262 Compiler_Info : System.Address;
263 -- Pointer to compiler-generated record representing protected object
264
265 Call_In_Progress : Entry_Call_Link;
266 -- Pointer to the entry call being executed (if any)
267
268 Entry_Body : Entry_Body_Access;
269 -- Pointer to executable code for the entry body of the protected type
270
271 Entry_Queue : Entry_Call_Link;
272 -- Place to store the waiting entry call (if any)
273 end record;
274
275 end System.Tasking.Protected_Objects.Single_Entry;