File : s-tarest.ads
1 ------------------------------------------------------------------------------
2 -- --
3 -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
4 -- --
5 -- S Y S T E M . T A S K I N G . R E S T R I C T E D . S T A G E S --
6 -- --
7 -- S p e c --
8 -- --
9 -- Copyright (C) 1992-2014, Free Software Foundation, Inc. --
10 -- --
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. --
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 is a simplified version of the System.Tasking.Stages package,
33 -- intended to be used in a restricted run time.
34
35 -- This package represents the high level tasking interface used by the
36 -- compiler to expand Ada 95 tasking constructs into simpler run time calls
37 -- (aka GNARLI, GNU Ada Run-time Library Interface)
38
39 -- Note: the compiler generates direct calls to this interface, via Rtsfind.
40 -- Any changes to this interface may require corresponding compiler changes
41 -- in exp_ch9.adb and possibly exp_ch7.adb
42
43 -- The restricted GNARLI is also composed of System.Protected_Objects and
44 -- System.Protected_Objects.Single_Entry
45
46 with System.Task_Info;
47 with System.Parameters;
48
49 package System.Tasking.Restricted.Stages is
50 pragma Elaborate_Body;
51
52 ---------------------------------
53 -- Compiler Interface (GNARLI) --
54 ---------------------------------
55
56 -- The compiler will expand in the GNAT tree the following construct:
57
58 -- task type T (Discr : Integer);
59
60 -- task body T is
61 -- ...declarations, possibly some controlled...
62 -- begin
63 -- ...B...;
64 -- end T;
65
66 -- T1 : T (1);
67
68 -- as follows:
69
70 -- task type t (discr : integer);
71 -- tE : aliased boolean := false;
72 -- tZ : size_type := unspecified_size;
73
74 -- type tV (discr : integer) is limited record
75 -- _task_id : task_id;
76 -- _atcb : aliased system__tasking__ada_task_control_block (0);
77 -- end record;
78
79 -- procedure tB (_task : access tV);
80 -- freeze tV [
81 -- procedure tVIP (_init : in out tV; _master : master_id;
82 -- _chain : in out activation_chain; _task_name : in string;
83 -- discr : integer) is
84 -- begin
85 -- _init.discr := discr;
86 -- _init._task_id := null;
87 -- system__tasking__ada_task_control_blockIP (_init._atcb, 0);
88 -- _init._task_id := _init._atcb'unchecked_access;
89 -- create_restricted_task (unspecified_priority, tZ,
90 -- unspecified_task_info, unspecified_cpu,
91 -- task_procedure_access!(tB'address), _init'address,
92 -- tE'unchecked_access, _task_name, _init._task_id);
93 -- return;
94 -- end tVIP;
95
96 -- _chain : aliased activation_chain;
97 -- activation_chainIP (_chain);
98
99 -- procedure tB (_task : access tV) is
100 -- discr : integer renames _task.discr;
101
102 -- procedure _clean is
103 -- begin
104 -- complete_restricted_task;
105 -- finalize_list (F14b);
106 -- return;
107 -- end _clean;
108
109 -- begin
110 -- ...declarations...
111 -- complete_restricted_activation;
112 -- ...B...;
113 -- return;
114 -- at end
115 -- _clean;
116 -- end tB;
117
118 -- tE := true;
119 -- t1 : t (1);
120 -- t1S : constant String := "t1";
121 -- tIP (t1, 3, _chain, t1S, 1);
122
123 Partition_Elaboration_Policy : Character := 'C';
124 pragma Export (C, Partition_Elaboration_Policy,
125 "__gnat_partition_elaboration_policy");
126 -- Partition elaboration policy. Value can be either 'C' for concurrent,
127 -- which is the default or 'S' for sequential. This value can be modified
128 -- by the binder generated code, before calling elaboration code.
129
130 procedure Create_Restricted_Task
131 (Priority : Integer;
132 Stack_Address : System.Address;
133 Size : System.Parameters.Size_Type;
134 Task_Info : System.Task_Info.Task_Info_Type;
135 CPU : Integer;
136 State : Task_Procedure_Access;
137 Discriminants : System.Address;
138 Elaborated : Access_Boolean;
139 Chain : in out Activation_Chain;
140 Task_Image : String;
141 Created_Task : Task_Id);
142 -- Compiler interface only. Do not call from within the RTS.
143 -- This must be called to create a new task, when the partition
144 -- elaboration policy is not specified (or is concurrent).
145 --
146 -- Priority is the task's priority (assumed to be in the
147 -- System.Any_Priority'Range)
148 --
149 -- Stack_Address is the start address of the stack associated to the task,
150 -- in case it has been preallocated by the compiler; it is equal to
151 -- Null_Address when the stack needs to be allocated by the underlying
152 -- operating system.
153 --
154 -- Size is the stack size of the task to create
155 --
156 -- Task_Info is the task info associated with the created task, or
157 -- Unspecified_Task_Info if none.
158 --
159 -- CPU is the task affinity. We pass it as an Integer to avoid an explicit
160 -- dependency from System.Multiprocessors when not needed. Static range
161 -- checks are performed when analyzing the pragma, and dynamic ones are
162 -- performed before setting the affinity at run time.
163 --
164 -- State is the compiler generated task's procedure body
165 --
166 -- Discriminants is a pointer to a limited record whose discriminants are
167 -- those of the task to create. This parameter should be passed as the
168 -- single argument to State.
169 --
170 -- Elaborated is a pointer to a Boolean that must be set to true on exit
171 -- if the task could be successfully elaborated.
172 --
173 -- Chain is a linked list of task that needs to be created. On exit,
174 -- Created_Task.Activation_Link will be Chain.T_ID, and Chain.T_ID will be
175 -- Created_Task (the created task will be linked at the front of Chain).
176 --
177 -- Task_Image is a string created by the compiler that the run time can
178 -- store to ease the debugging and the Ada.Task_Identification facility.
179 --
180 -- Created_Task is the resulting task.
181 --
182 -- This procedure can raise Storage_Error if the task creation fails
183
184 procedure Create_Restricted_Task_Sequential
185 (Priority : Integer;
186 Stack_Address : System.Address;
187 Size : System.Parameters.Size_Type;
188 Task_Info : System.Task_Info.Task_Info_Type;
189 CPU : Integer;
190 State : Task_Procedure_Access;
191 Discriminants : System.Address;
192 Elaborated : Access_Boolean;
193 Task_Image : String;
194 Created_Task : Task_Id);
195 -- Compiler interface only. Do not call from within the RTS.
196 -- This must be called to create a new task, when the sequential partition
197 -- elaboration policy is used.
198 --
199 -- The parameters are the same as Create_Restricted_Task except there is
200 -- no Chain parameter (for the activation chain), as there is only one
201 -- global activation chain, which is declared in the body of this package.
202
203 procedure Activate_Restricted_Tasks
204 (Chain_Access : Activation_Chain_Access);
205 -- Compiler interface only. Do not call from within the RTS.
206 -- This must be called by the creator of a chain of one or more new tasks,
207 -- to activate them. The chain is a linked list that up to this point is
208 -- only known to the task that created them, though the individual tasks
209 -- are already in the All_Tasks_List.
210 --
211 -- The compiler builds the chain in LIFO order (as a stack). Another
212 -- version of this procedure had code to reverse the chain, so as to
213 -- activate the tasks in the order of declaration. This might be nice, but
214 -- it is not needed if priority-based scheduling is supported, since all
215 -- the activated tasks synchronize on the activators lock before they start
216 -- activating and so they should start activating in priority order.
217 --
218 -- When the partition elaboration policy is sequential, this procedure
219 -- does nothing, tasks will be activated at end of elaboration.
220
221 procedure Activate_All_Tasks_Sequential;
222 pragma Export (C, Activate_All_Tasks_Sequential,
223 "__gnat_activate_all_tasks");
224 -- Binder interface only. Do not call from within the RTS. This must be
225 -- called an the end of the elaboration to activate all tasks, in order
226 -- to implement the sequential elaboration policy.
227
228 procedure Complete_Restricted_Activation;
229 -- Compiler interface only. Do not call from within the RTS. This should be
230 -- called from the task body at the end of the elaboration code for its
231 -- declarative part. Decrement the count of tasks to be activated by the
232 -- activator and wake it up so it can check to see if all tasks have been
233 -- activated. Except for the environment task, which should never call this
234 -- procedure, T.Activator should only be null iff T has completed
235 -- activation.
236
237 procedure Complete_Restricted_Task;
238 -- Compiler interface only. Do not call from within the RTS. This should be
239 -- called from an implicit at-end handler associated with the task body,
240 -- when it completes. From this point, the current task will become not
241 -- callable. If the current task have not completed activation, this should
242 -- be done now in order to wake up the activator (the environment task).
243
244 function Restricted_Terminated (T : Task_Id) return Boolean;
245 -- Compiler interface only. Do not call from within the RTS. This is called
246 -- by the compiler to implement the 'Terminated attribute.
247 --
248 -- source code:
249 -- T1'Terminated
250 --
251 -- code expansion:
252 -- restricted_terminated (t1._task_id)
253
254 procedure Finalize_Global_Tasks;
255 -- This is needed to support the compiler interface. It will only be called
256 -- by the Environment task in the binder generated file (by adafinal).
257 -- Instead, it will cause the Environment to block forever, since none of
258 -- the dependent tasks are expected to terminate
259
260 end System.Tasking.Restricted.Stages;