gcc/ada/s-tasini.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                GNU ADA 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 --                                                                          --
  10 --          Copyright (C) 1992-2001, Free Software Foundation, Inc.         --
  11 --                                                                          --
  12 -- GNARL is free software; you can  redistribute it  and/or modify it under --
  13 -- terms of the  GNU General Public License as published  by the Free Soft- --
  14 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  15 -- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
  16 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  17 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  18 -- for  more details.  You should have  received  a copy of the GNU General --
  19 -- Public License  distributed with GNARL; see file COPYING.  If not, write --
  20 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  21 -- MA 02111-1307, USA.                                                      --
  22 --                                                                          --
  23 -- As a special exception,  if other files  instantiate  generics from this --
  24 -- unit, or you link  this unit with other files  to produce an executable, --
  25 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  26 -- covered  by the  GNU  General  Public  License.  This exception does not --
  27 -- however invalidate  any other reasons why  the executable file  might be --
  28 -- covered by the  GNU Public License.                                      --
  29 --                                                                          --
  30 -- GNARL was developed by the GNARL team at Florida State University. It is --
  31 -- now maintained by Ada Core Technologies, Inc. (http://www.gnat.com).     --
  32 --                                                                          --
  33 ------------------------------------------------------------------------------
  34
  35 --  This package provides overall initialization of the tasking portion of the
  36 --  RTS. This package must be elaborated before any tasking features are used.
  37
  38 package System.Tasking.Initialization is
  39
  40    procedure Remove_From_All_Tasks_List (T : Task_ID);
  41    --  Remove T from All_Tasks_List.
  42    --  Call this function with RTS_Lock taken.
  43
  44    ---------------------------------
  45    -- Tasking-Specific Soft Links --
  46    ---------------------------------
  47
  48    --  These permit us to leave out certain portions of the tasking
  49    --  run-time system if they are not used.  They are only used internally
  50    --  by the tasking run-time system.
  51    --  So far, the only example is support for Ada.Task_Attributes.
  52
  53    type Proc_T is access procedure (T : Task_ID);
  54
  55    procedure Finalize_Attributes (T : Task_ID);
  56    procedure Initialize_Attributes (T : Task_ID);
  57
  58    Finalize_Attributes_Link : Proc_T := Finalize_Attributes'Access;
  59    --  should be called with abortion deferred and T.L write-locked
  60
  61    Initialize_Attributes_Link : Proc_T := Initialize_Attributes'Access;
  62    --  should be called with abortion deferred, but holding no locks
  63
  64    -------------------------
  65    -- Abort Defer/Undefer --
  66    -------------------------
  67
  68    --  Defer_Abort defers the affects of low-level abort and priority change
  69    --  in the calling task until a matching Undefer_Abort call is executed.
  70
  71    --  Undefer_Abort DOES MORE than just undo the effects of one call to
  72    --  Defer_Abort.  It is the universal "polling point" for deferred
  73    --  processing, including the following:
  74
  75    --  1) base priority changes
  76
  77    --  2) abort/ATC
  78
  79    --  Abort deferral MAY be nested (Self_ID.Deferral_Level is a count),
  80    --  but to avoid waste and undetected errors, it generally SHOULD NOT
  81    --  be nested.  The symptom of over-deferring abort is that an exception
  82    --  may fail to be raised, or an abort may fail to take place.
  83
  84    --  Therefore, there are two sets of the inlinable defer/undefer
  85    --  routines, which are the ones to be used inside GNARL.
  86    --  One set allows nesting.  The other does not.  People who
  87    --  maintain the GNARL should try to avoid using the nested versions,
  88    --  or at least look very critically at the places where they are
  89    --  used.
  90
  91    --  In general, any GNARL call that is potentially blocking, or
  92    --  whose semantics require that it sometimes raise an exception,
  93    --  or that is required to be an abort completion point, must be
  94    --  made with abort Deferral_Level = 1.
  95
  96    --  In general, non-blocking GNARL calls, which may be made from inside
  97    --  a protected action, are likely to need to allow nested abort
  98    --  deferral.
  99
 100    --  With some critical exceptions (which are supposed to be documented),
 101    --  internal calls to the tasking runtime system assume abort is already
 102    --  deferred, and do not modify the deferral level.
 103
 104    --  There is also a set of non-linable defer/undefer routines,
 105    --  for direct call from the compiler. These are not in-lineable
 106    --  because they may need to be called via pointers ("soft links").
 107    --  For the sake of efficiency, the version with Self_ID as parameter
 108    --  should used wherever possible. These are all nestable.
 109
 110    --  Non-nestable inline versions  --
 111
 112    procedure Defer_Abort (Self_ID : Task_ID);
 113    pragma Inline (Defer_Abort);
 114
 115    procedure Undefer_Abort (Self_ID : Task_ID);
 116    pragma Inline (Undefer_Abort);
 117
 118    --  Nestable inline versions  --
 119
 120    procedure Defer_Abort_Nestable (Self_ID : Task_ID);
 121    pragma Inline (Defer_Abort_Nestable);
 122
 123    procedure Undefer_Abort_Nestable (Self_ID : Task_ID);
 124    pragma Inline (Undefer_Abort_Nestable);
 125
 126    --  NON-INLINE versions without Self_ID for code generated by the
 127    --  expander and for soft links
 128
 129    procedure Defer_Abortion;
 130    procedure Undefer_Abortion;
 131
 132    --  ?????
 133    --  Try to phase out all uses of the above versions.
 134
 135    function Check_Abort_Status return Integer;
 136    --  Returns Boolean'Pos (True) iff abort signal should raise
 137    --  Standard.Abort_Signal. Only used by IRIX currently.
 138
 139    ---------------------------
 140    --  Change Base Priority --
 141    ---------------------------
 142
 143    procedure Change_Base_Priority (T : Task_ID);
 144    --  Change the base priority of T.
 145    --  Has to be called with the affected task's ATCB write-locked.
 146    --  May temporariliy release the lock.
 147
 148    procedure Poll_Base_Priority_Change (Self_ID : Task_ID);
 149    --  Has to be called with Self_ID's ATCB write-locked.
 150    --  May temporariliy release the lock.
 151    pragma Inline (Poll_Base_Priority_Change);
 152
 153    ----------------------
 154    -- Task Lock/Unlock --
 155    ----------------------
 156
 157    procedure Task_Lock (Self_ID : Task_ID);
 158    pragma Inline (Task_Lock);
 159
 160    procedure Task_Unlock (Self_ID : Task_ID);
 161    pragma Inline (Task_Unlock);
 162    --  These are versions of Lock_Task and Unlock_Task created for use
 163    --  within the GNARL.
 164
 165    procedure Final_Task_Unlock (Self_ID : Task_ID);
 166    --  This version is only for use in Terminate_Task, when the task
 167    --  is relinquishing further rights to its own ATCB.
 168    --  There is a very interesting potential race condition there, where
 169    --  the old task may run concurrently with a new task that is allocated
 170    --  the old tasks (now reused) ATCB.  The critical thing here is to
 171    --  not make any reference to the ATCB after the lock is released.
 172    --  See also comments on Terminate_Task and Unlock.
 173
 174    procedure Wakeup_Entry_Caller
 175      (Self_ID    : Task_ID;
 176       Entry_Call : Entry_Call_Link;
 177       New_State  : Entry_Call_State);
 178    pragma Inline (Wakeup_Entry_Caller);
 179    --  This is called at the end of service of an entry call,
 180    --  to abort the caller if he is in an abortable part, and
 181    --  to wake up the caller if he is on Entry_Caller_Sleep.
 182    --  Call it holding the lock of Entry_Call.Self.
 183    --
 184    --  Timed_Call or Simple_Call:
 185    --    The caller is waiting on Entry_Caller_Sleep, in
 186    --    Wait_For_Completion, or Wait_For_Completion_With_Timeout.
 187    --
 188    --  Conditional_Call:
 189    --    The caller might be in Wait_For_Completion,
 190    --    waiting for a rendezvous (possibly requeued without abort)
 191    --    to complete.
 192    --
 193    --  Asynchronous_Call:
 194    --    The caller may be executing in the abortable part o
 195    --    an async. select, or on a time delay,
 196    --    if Entry_Call.State >= Was_Abortable.
 197
 198    procedure Locked_Abort_To_Level
 199      (Self_ID : Task_ID;
 200       T       : Task_ID;
 201       L       : ATC_Level);
 202    pragma Inline (Locked_Abort_To_Level);
 203    --  Abort a task to a specified ATC level.
 204    --  Call this only with T locked.
 205
 206 end System.Tasking.Initialization;