File : s-tasini.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 . I N I T I A L I Z A T I O N --
6 -- --
7 -- S p e c --
8 -- --
9 -- Copyright (C) 1992-2014, 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 package provides overall initialization of the tasking portion of the
33 -- RTS. This package must be elaborated before any tasking features are used.
34
35 package 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);
175 pragma Inline (Locked_Abort_To_Level);
176 -- Abort a task to a specified ATC level. Call this only with T locked
177
178 end System.Tasking.Initialization;