1------------------------------------------------------------------------------
2--                                                                          --
3--                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --
4--                                                                          --
5--                        S Y S T E M . T A S K I N G                       --
6--                                                                          --
7--                                  B o d y                                 --
8--                                                                          --
9--          Copyright (C) 1992-2019, 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-- 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.               --
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
32pragma Polling (Off);
33--  Turn off polling, we do not want ATC polling to take place during tasking
34--  operations. It causes infinite loops and other problems.
35
36with System.Task_Primitives.Operations;
37with System.Storage_Elements;
38
39package body System.Tasking is
40
41   package STPO renames System.Task_Primitives.Operations;
42
43   ---------------------
44   -- Detect_Blocking --
45   ---------------------
46
47   function Detect_Blocking return Boolean is
48      GL_Detect_Blocking : Integer;
49      pragma Import (C, GL_Detect_Blocking, "__gl_detect_blocking");
50      --  Global variable exported by the binder generated file. A value equal
51      --  to 1 indicates that pragma Detect_Blocking is active, while 0 is used
52      --  for the pragma not being present.
53
54   begin
55      return GL_Detect_Blocking = 1;
56   end Detect_Blocking;
57
58   -----------------------
59   -- Number_Of_Entries --
60   -----------------------
61
62   function Number_Of_Entries (Self_Id : Task_Id) return Entry_Index is
63   begin
64      return Entry_Index (Self_Id.Entry_Num);
65   end Number_Of_Entries;
66
67   ----------
68   -- Self --
69   ----------
70
71   function Self return Task_Id renames STPO.Self;
72
73   ------------------
74   -- Storage_Size --
75   ------------------
76
77   function Storage_Size (T : Task_Id) return System.Parameters.Size_Type is
78   begin
79      return
80         System.Parameters.Size_Type
81           (T.Common.Compiler_Data.Pri_Stack_Info.Size);
82   end Storage_Size;
83
84   ---------------------
85   -- Initialize_ATCB --
86   ---------------------
87
88   procedure Initialize_ATCB
89     (Self_ID              : Task_Id;
90      Task_Entry_Point     : Task_Procedure_Access;
91      Task_Arg             : System.Address;
92      Parent               : Task_Id;
93      Elaborated           : Access_Boolean;
94      Base_Priority        : System.Any_Priority;
95      Base_CPU             : System.Multiprocessors.CPU_Range;
96      Domain               : Dispatching_Domain_Access;
97      Task_Info            : System.Task_Info.Task_Info_Type;
98      Stack_Size           : System.Parameters.Size_Type;
99      T                    : Task_Id;
100      Success              : out Boolean)
101   is
102   begin
103      T.Common.State := Unactivated;
104
105      --  Initialize T.Common.LL
106
107      STPO.Initialize_TCB (T, Success);
108
109      if not Success then
110         return;
111      end if;
112
113      --  Note that use of an aggregate here for this assignment
114      --  would be illegal, because Common_ATCB is limited because
115      --  Task_Primitives.Private_Data is limited.
116
117      T.Common.Parent                   := Parent;
118      T.Common.Base_Priority            := Base_Priority;
119      T.Common.Base_CPU                 := Base_CPU;
120
121      --  The Domain defaults to that of the activator. But that can be null in
122      --  the case of foreign threads (see Register_Foreign_Thread), in which
123      --  case we default to the System_Domain.
124
125      if Domain /= null then
126         T.Common.Domain := Domain;
127      elsif Self_ID.Common.Domain /= null then
128         T.Common.Domain := Self_ID.Common.Domain;
129      else
130         T.Common.Domain := System_Domain;
131      end if;
132      pragma Assert (T.Common.Domain /= null);
133
134      T.Common.Current_Priority         := 0;
135      T.Common.Protected_Action_Nesting := 0;
136      T.Common.Call                     := null;
137      T.Common.Task_Arg                 := Task_Arg;
138      T.Common.Task_Entry_Point         := Task_Entry_Point;
139      T.Common.Activator                := Self_ID;
140      T.Common.Wait_Count               := 0;
141      T.Common.Elaborated               := Elaborated;
142      T.Common.Activation_Failed        := False;
143      T.Common.Task_Info                := Task_Info;
144      T.Common.Global_Task_Lock_Nesting := 0;
145      T.Common.Fall_Back_Handler        := null;
146      T.Common.Specific_Handler         := null;
147      T.Common.Debug_Events             := (others => False);
148      T.Common.Task_Image_Len           := 0;
149
150      if T.Common.Parent = null then
151
152         --  For the environment task, the adjusted stack size is meaningless.
153         --  For example, an unspecified Stack_Size means that the stack size
154         --  is determined by the environment, or can grow dynamically. The
155         --  Stack_Checking algorithm therefore needs to use the requested
156         --  size, or 0 in case of an unknown size.
157
158         T.Common.Compiler_Data.Pri_Stack_Info.Size :=
159            Storage_Elements.Storage_Offset (Stack_Size);
160
161      else
162         T.Common.Compiler_Data.Pri_Stack_Info.Size :=
163           Storage_Elements.Storage_Offset
164             (Parameters.Adjust_Storage_Size (Stack_Size));
165      end if;
166
167      --  Link the task into the list of all tasks
168
169      T.Common.All_Tasks_Link := All_Tasks_List;
170      All_Tasks_List := T;
171   end Initialize_ATCB;
172
173   ----------------
174   -- Initialize --
175   ----------------
176
177   Main_Task_Image : constant String := "main_task";
178   --  Image of environment task
179
180   Main_Priority : Integer;
181   pragma Import (C, Main_Priority, "__gl_main_priority");
182   --  Priority for main task. Note that this is of type Integer, not Priority,
183   --  because we use the value -1 to indicate the default main priority, and
184   --  that is of course not in Priority'range.
185
186   Main_CPU : Integer;
187   pragma Import (C, Main_CPU, "__gl_main_cpu");
188   --  Affinity for main task. Note that this is of type Integer, not
189   --  CPU_Range, because we use the value -1 to indicate the unassigned
190   --  affinity, and that is of course not in CPU_Range'Range.
191
192   Initialized : Boolean := False;
193   --  Used to prevent multiple calls to Initialize
194
195   procedure Initialize is
196      T             : Task_Id;
197      Base_Priority : Any_Priority;
198      Base_CPU      : System.Multiprocessors.CPU_Range;
199      Success       : Boolean;
200
201      use type System.Multiprocessors.CPU_Range;
202
203   begin
204      if Initialized then
205         return;
206      end if;
207
208      Initialized := True;
209
210      --  Initialize Environment Task
211
212      Base_Priority :=
213        (if Main_Priority = Unspecified_Priority
214         then Default_Priority
215         else Priority (Main_Priority));
216
217      Base_CPU :=
218        (if Main_CPU = Unspecified_CPU
219         then System.Multiprocessors.Not_A_Specific_CPU
220         else System.Multiprocessors.CPU_Range (Main_CPU));
221
222      --  At program start-up the environment task is allocated to the default
223      --  system dispatching domain.
224      --  Make sure that the processors which are not available are not taken
225      --  into account. Use Number_Of_CPUs to know the exact number of
226      --  processors in the system at execution time.
227
228      System_Domain :=
229        new Dispatching_Domain'
230          (Multiprocessors.CPU'First .. Multiprocessors.Number_Of_CPUs =>
231             True);
232
233      T := STPO.New_ATCB (0);
234      Initialize_ATCB
235        (Self_ID              => null,
236         Task_Entry_Point     => null,
237         Task_Arg             => Null_Address,
238         Parent               => Null_Task,
239         Elaborated           => null,
240         Base_Priority        => Base_Priority,
241         Base_CPU             => Base_CPU,
242         Domain               => System_Domain,
243         Task_Info            => Task_Info.Unspecified_Task_Info,
244         Stack_Size           => 0,
245         T                    => T,
246         Success              => Success);
247      pragma Assert (Success);
248
249      STPO.Initialize (T);
250      STPO.Set_Priority (T, T.Common.Base_Priority);
251      T.Common.State := Runnable;
252      T.Common.Task_Image_Len := Main_Task_Image'Length;
253      T.Common.Task_Image (Main_Task_Image'Range) := Main_Task_Image;
254
255      Dispatching_Domain_Tasks :=
256        new Array_Allocated_Tasks'
257          (Multiprocessors.CPU'First .. Multiprocessors.Number_Of_CPUs => 0);
258
259      --  Signal that this task is being allocated to a processor
260
261      if Base_CPU /= System.Multiprocessors.Not_A_Specific_CPU then
262
263         --  Increase the number of tasks attached to the CPU to which this
264         --  task is allocated.
265
266         Dispatching_Domain_Tasks (Base_CPU) :=
267           Dispatching_Domain_Tasks (Base_CPU) + 1;
268      end if;
269
270      --  The full initialization of the environment task's Entry_Calls array
271      --  is deferred to Init_RTS because only the first element of the array
272      --  is used by the restricted Ravenscar runtime.
273
274      T.Entry_Calls (T.Entry_Calls'First).Self := T;
275      T.Entry_Calls (T.Entry_Calls'First).Level := T.Entry_Calls'First;
276
277   end Initialize;
278end System.Tasking;
279