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   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 -- 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
  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;