1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
5 -- SYSTEM.TASKING.PROTECTED_OBJECTS.SINGLE_ENTRY --
9 -- Copyright (C) 1992-2016, Free Software Foundation, Inc. --
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. --
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 provides an optimized version of Protected_Objects.Operations
33 -- and Protected_Objects.Entries making the following assumptions:
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)
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).
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)
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
57 package System
.Tasking
.Protected_Objects
.Single_Entry
is
58 pragma Elaborate_Body
;
60 ---------------------------------
61 -- Compiler Interface (GNARLI) --
62 ---------------------------------
64 -- The compiler will expand in the GNAT tree the following construct:
70 -- Open : Boolean := False;
73 -- protected body PO is
74 -- entry E when Open is
75 -- ...variable declarations...
81 -- ...variable declarations...
89 -- protected type poT is
93 -- open : boolean := false;
95 -- type poTV is limited record
96 -- open : boolean := false;
97 -- _object : aliased protection_entry;
99 -- procedure poPT__E1s (O : address; P : address; E :
100 -- protected_entry_index);
101 -- function poPT__B2s (O : address; E : protected_entry_index) return
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);
109 -- procedure poTVIP (_init : in out poTV) is
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);
120 -- poTVIP (poTV!(po));
122 -- function poPT__B2s (O : address; E : protected_entry_index) return
124 -- type poTVP is access poTV;
125 -- _object : poTVP := poTVP!(O);
126 -- poR : protection_entry renames _object._object;
127 -- openP : boolean renames _object.open;
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);
138 -- poR : protection_entry renames _object._object;
139 -- openP : boolean renames _object.open;
140 -- ...variable declarations...
144 -- complete_single_entry_body (_object._object'unchecked_access);
147 -- when all others =>
148 -- exceptional_complete_single_entry_body (_object._object'
149 -- unchecked_access, get_gnat_exception);
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...
162 -- procedure poPT__pP (_object : in out poTV) is
163 -- procedure _clean is
165 -- service_entry (_object._object'unchecked_access);
169 -- lock_entry (_object._object'unchecked_access);
171 -- poPT__pN (_object);
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.
183 type Protection_Entry_Access
is access all Protection_Entry
;
185 type Entry_Body_Access
is access constant Entry_Body
;
186 -- Access to barrier and action function of an entry
188 procedure Initialize_Protection_Entry
189 (Object
: Protection_Entry_Access
;
190 Ceiling_Priority
: Integer;
191 Compiler_Info
: System
.Address
;
192 Entry_Body
: Entry_Body_Access
);
193 -- Initialize the Object parameter so that it can be used by the run time
194 -- to keep track of the runtime state of a protected object.
196 procedure Lock_Entry
(Object
: Protection_Entry_Access
);
197 -- Lock a protected object for write access. Upon return, the caller owns
198 -- the lock to this object, and no other call to Lock or Lock_Read_Only
199 -- with the same argument will return until the corresponding call to
200 -- Unlock has been made by the caller.
202 procedure Lock_Read_Only_Entry
203 (Object
: Protection_Entry_Access
);
204 -- Lock a protected object for read access. Upon return, the caller owns
205 -- the lock for read access, and no other calls to Lock with the same
206 -- argument will return until the corresponding call to Unlock has been
207 -- made by the caller. Other calls to Lock_Read_Only may (but need not)
208 -- return before the call to Unlock, and the corresponding callers will
209 -- also own the lock for read access.
211 procedure Unlock_Entry
(Object
: Protection_Entry_Access
);
212 -- Relinquish ownership of the lock for the object represented by the
213 -- Object parameter. If this ownership was for write access, or if it was
214 -- for read access where there are no other read access locks outstanding,
215 -- one (or more, in the case of Lock_Read_Only) of the tasks waiting on
216 -- this lock (if any) will be given the lock and allowed to return from
217 -- the Lock or Lock_Read_Only call.
219 procedure Service_Entry
(Object
: Protection_Entry_Access
);
220 -- Service the entry queue of the specified object, executing the
221 -- corresponding body of any queued entry call that is waiting on True
222 -- barrier. This is used when the state of a protected object may have
223 -- changed, in particular after the execution of the statement sequence
224 -- of a protected procedure.
226 -- This must be called with abort deferred and with the corresponding
227 -- object locked. Object is unlocked on return.
229 procedure Protected_Single_Entry_Call
230 (Object
: Protection_Entry_Access
;
231 Uninterpreted_Data
: System
.Address
);
232 -- Make a protected entry call to the specified object
234 -- Pends a protected entry call on the protected object represented by
235 -- Object. A pended call is not queued; it may be executed immediately
236 -- or queued, depending on the state of the entry barrier.
238 -- Uninterpreted_Data
239 -- This will be returned by Next_Entry_Call when this call is serviced.
240 -- It can be used by the compiler to pass information between the
241 -- caller and the server, in particular entry parameters.
243 procedure Exceptional_Complete_Single_Entry_Body
244 (Object
: Protection_Entry_Access
;
245 Ex
: Ada
.Exceptions
.Exception_Id
);
246 -- Perform all of the functions of Complete_Entry_Body. In addition, report
247 -- in Ex the exception whose propagation terminated the entry body to the
250 function Protected_Count_Entry
(Object
: Protection_Entry
) return Natural;
251 -- Return the number of entry calls on Object (0 or 1)
253 function Protected_Single_Entry_Caller
254 (Object
: Protection_Entry
) return Task_Id
;
255 -- Return value of E'Caller, where E is the protected entry currently being
256 -- handled. This will only work if called from within an entry body, as
257 -- required by the LRM (C.7.1(14)).
260 type Protection_Entry
is record
261 Common
: aliased Protection
;
262 -- State of the protected object. This part is common to any protected
263 -- object, including those without entries.
265 Compiler_Info
: System
.Address
;
266 -- Pointer to compiler-generated record representing protected object
268 Call_In_Progress
: Entry_Call_Link
;
269 -- Pointer to the entry call being executed (if any)
271 Entry_Body
: Entry_Body_Access
;
272 -- Pointer to executable code for the entry body of the protected type
274 Entry_Queue
: Entry_Call_Link
;
275 -- Place to store the waiting entry call (if any)
278 end System
.Tasking
.Protected_Objects
.Single_Entry
;