1------------------------------------------------------------------------------
2--                                                                          --
3--                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --
4--                                                                          --
5--         S Y S T E M . T A S K I N G . I N I T I A L I Z A T I O N        --
6--                                                                          --
7--                                  S p e c                                 --
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
32--  This package provides overall initialization of the tasking portion of the
33--  RTS. This package must be elaborated before any tasking features are used.
34
35package System.Tasking.Initialization is
36
37   procedure Remove_From_All_Tasks_List (T : Task_Id);
38   --  Remove T from All_Tasks_List. Call this function with RTS_Lock taken
39
40   procedure Finalize_Attributes (T : Task_Id);
41   --  Finalize all attributes from T. This is to be called just before the
42   --  ATCB is deallocated. It relies on the caller holding T.L write-lock
43   --  on entry.
44
45   ---------------------------------
46   -- Tasking-Specific Soft Links --
47   ---------------------------------
48
49   -------------------------
50   -- Abort Defer/Undefer --
51   -------------------------
52
53   --  Defer_Abort defers the effects of low-level abort and priority change
54   --  in the calling task until a matching Undefer_Abort call is executed.
55
56   --  Undefer_Abort DOES MORE than just undo the effects of one call to
57   --  Defer_Abort. It is the universal "polling point" for deferred
58   --  processing, including the following:
59
60   --  1) base priority changes
61
62   --  2) abort/ATC
63
64   --  Abort deferral MAY be nested (Self_ID.Deferral_Level is a count), but
65   --  to avoid waste and undetected errors, it generally SHOULD NOT be
66   --  nested. The symptom of over-deferring abort is that an exception may
67   --  fail to be raised, or an abort may fail to take place.
68
69   --  Therefore, there are two sets of the inlineable defer/undefer routines,
70   --  which are the ones to be used inside GNARL. One set allows nesting. The
71   --  other does not. People who maintain the GNARL should try to avoid using
72   --  the nested versions, or at least look very critically at the places
73   --  where they are used.
74
75   --  In general, any GNARL call that is potentially blocking, or whose
76   --  semantics require that it sometimes raise an exception, or that is
77   --  required to be an abort completion point, must be made with abort
78   --  Deferral_Level = 1.
79
80   --  In general, non-blocking GNARL calls, which may be made from inside a
81   --  protected action, are likely to need to allow nested abort deferral.
82
83   --  With some critical exceptions (which are supposed to be documented),
84   --  internal calls to the tasking runtime system assume abort is already
85   --  deferred, and do not modify the deferral level.
86
87   --  There is also a set of non-inlineable defer/undefer routines, for direct
88   --  call from the compiler. These are not inlineable because they may need
89   --  to be called via pointers ("soft links"). For the sake of efficiency,
90   --  the version with Self_ID as parameter should used wherever possible.
91   --  These are all nestable.
92
93   --  Non-nestable inline versions
94
95   procedure Defer_Abort (Self_ID : Task_Id);
96   pragma Inline (Defer_Abort);
97
98   procedure Undefer_Abort (Self_ID : Task_Id);
99   pragma Inline (Undefer_Abort);
100
101   --  Nestable inline versions
102
103   procedure Defer_Abort_Nestable (Self_ID : Task_Id);
104   pragma Inline (Defer_Abort_Nestable);
105
106   procedure Undefer_Abort_Nestable (Self_ID : Task_Id);
107   pragma Inline (Undefer_Abort_Nestable);
108
109   procedure Do_Pending_Action (Self_ID : Task_Id);
110   --  Only call with no locks, and when Self_ID.Pending_Action = True Perform
111   --  necessary pending actions (e.g. abort, priority change). This procedure
112   --  is usually called when needed as a result of calling Undefer_Abort,
113   --  although in the case of e.g. No_Abort restriction, it can be necessary
114   --  to force execution of pending actions.
115
116   function Check_Abort_Status return Integer;
117   --  Returns Boolean'Pos (True) iff abort signal should raise
118   --  Standard'Abort_Signal. Only used by IRIX currently.
119
120   --------------------------
121   -- Change Base Priority --
122   --------------------------
123
124   procedure Change_Base_Priority (T : Task_Id);
125   --  Change the base priority of T. Has to be called with the affected
126   --  task's ATCB write-locked. May temporarily release the lock.
127
128   ----------------------
129   -- Task Lock/Unlock --
130   ----------------------
131
132   procedure Task_Lock (Self_ID : Task_Id);
133   pragma Inline (Task_Lock);
134
135   procedure Task_Unlock (Self_ID : Task_Id);
136   pragma Inline (Task_Unlock);
137   --  These are versions of Lock_Task and Unlock_Task created for use
138   --  within the GNARL.
139
140   procedure Final_Task_Unlock (Self_ID : Task_Id);
141   --  This version is only for use in Terminate_Task, when the task is
142   --  relinquishing further rights to its own ATCB. There is a very
143   --  interesting potential race condition there, where the old task may run
144   --  concurrently with a new task that is allocated the old tasks (now
145   --  reused) ATCB. The critical thing here is to not make any reference to
146   --  the ATCB after the lock is released. See also comments on
147   --  Terminate_Task and Unlock.
148
149   procedure Wakeup_Entry_Caller
150     (Self_ID    : Task_Id;
151      Entry_Call : Entry_Call_Link;
152      New_State  : Entry_Call_State);
153   pragma Inline (Wakeup_Entry_Caller);
154   --  This is called at the end of service of an entry call, to abort the
155   --  caller if he is in an abortable part, and to wake up the caller if he
156   --  is on Entry_Caller_Sleep. Call it holding the lock of Entry_Call.Self.
157   --
158   --  Timed_Call or Simple_Call:
159   --    The caller is waiting on Entry_Caller_Sleep, in Wait_For_Completion,
160   --    or Wait_For_Completion_With_Timeout.
161   --
162   --  Conditional_Call:
163   --    The caller might be in Wait_For_Completion,
164   --    waiting for a rendezvous (possibly requeued without abort) to
165   --    complete.
166   --
167   --  Asynchronous_Call:
168   --    The caller may be executing in the abortable part an async. select,
169   --    or on a time delay, if Entry_Call.State >= Was_Abortable.
170
171   procedure Locked_Abort_To_Level
172     (Self_ID : Task_Id;
173      T       : Task_Id;
174      L       : ATC_Level_Base);
175   pragma Inline (Locked_Abort_To_Level);
176   --  Abort a task to a specified ATC level. Call this only with T locked
177
178end System.Tasking.Initialization;
179