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 --          Copyright (C) 1992-2004, 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 2,  or (at your option) any later ver- --
  14 -- sion. GNARL 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.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNARL; see file COPYING.  If not, write --
  19 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  20 -- MA 02111-1307, USA.                                                      --
  21 --                                                                          --
  22 -- As a special exception,  if other files  instantiate  generics from this --
  23 -- unit, or you link  this unit with other files  to produce an executable, --
  24 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  25 -- covered  by the  GNU  General  Public  License.  This exception does not --
  26 -- however invalidate  any other reasons why  the executable file  might be --
  27 -- covered by the  GNU Public License.                                      --
  28 --                                                                          --
  29 -- GNARL was developed by the GNARL team at Florida State University.       --
  30 -- Extensive contributions were provided by Ada Core Technologies, Inc.     --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 --  This package provides overall initialization of the tasking portion of the
  35 --  RTS. This package must be elaborated before any tasking features are used.
  36
  37 package System.Tasking.Initialization is
  38
  39    procedure Remove_From_All_Tasks_List (T : Task_Id);
  40    --  Remove T from All_Tasks_List.
  41    --  Call this function with RTS_Lock taken.
  42
  43    ---------------------------------
  44    -- Tasking-Specific Soft Links --
  45    ---------------------------------
  46
  47    --  These permit us to leave out certain portions of the tasking
  48    --  run-time system if they are not used.  They are only used internally
  49    --  by the tasking run-time system.
  50    --  So far, the only example is support for Ada.Task_Attributes.
  51
  52    type Proc_T is access procedure (T : Task_Id);
  53
  54    procedure Finalize_Attributes (T : Task_Id);
  55    procedure Initialize_Attributes (T : Task_Id);
  56
  57    Finalize_Attributes_Link : Proc_T := Finalize_Attributes'Access;
  58    --  should be called with abortion deferred and T.L write-locked
  59
  60    Initialize_Attributes_Link : Proc_T := Initialize_Attributes'Access;
  61    --  should be called with abortion deferred, but holding no locks
  62
  63    -------------------------
  64    -- Abort Defer/Undefer --
  65    -------------------------
  66
  67    --  Defer_Abort defers the affects of low-level abort and priority change
  68    --  in the calling task until a matching Undefer_Abort call is executed.
  69
  70    --  Undefer_Abort DOES MORE than just undo the effects of one call to
  71    --  Defer_Abort.  It is the universal "polling point" for deferred
  72    --  processing, including the following:
  73
  74    --  1) base priority changes
  75
  76    --  2) abort/ATC
  77
  78    --  Abort deferral MAY be nested (Self_ID.Deferral_Level is a count),
  79    --  but to avoid waste and undetected errors, it generally SHOULD NOT
  80    --  be nested.  The symptom of over-deferring abort is that an exception
  81    --  may fail to be raised, or an abort may fail to take place.
  82
  83    --  Therefore, there are two sets of the inlinable defer/undefer
  84    --  routines, which are the ones to be used inside GNARL.
  85    --  One set allows nesting.  The other does not.  People who
  86    --  maintain the GNARL should try to avoid using the nested versions,
  87    --  or at least look very critically at the places where they are
  88    --  used.
  89
  90    --  In general, any GNARL call that is potentially blocking, or
  91    --  whose semantics require that it sometimes raise an exception,
  92    --  or that is required to be an abort completion point, must be
  93    --  made with abort Deferral_Level = 1.
  94
  95    --  In general, non-blocking GNARL calls, which may be made from inside
  96    --  a protected action, are likely to need to allow nested abort
  97    --  deferral.
  98
  99    --  With some critical exceptions (which are supposed to be documented),
 100    --  internal calls to the tasking runtime system assume abort is already
 101    --  deferred, and do not modify the deferral level.
 102
 103    --  There is also a set of non-linable defer/undefer routines,
 104    --  for direct call from the compiler. These are not in-lineable
 105    --  because they may need to be called via pointers ("soft links").
 106    --  For the sake of efficiency, the version with Self_ID as parameter
 107    --  should used wherever possible. These are all nestable.
 108
 109    --  Non-nestable inline versions
 110
 111    procedure Defer_Abort (Self_ID : Task_Id);
 112    pragma Inline (Defer_Abort);
 113
 114    procedure Undefer_Abort (Self_ID : Task_Id);
 115    pragma Inline (Undefer_Abort);
 116
 117    --  Nestable inline versions
 118
 119    procedure Defer_Abort_Nestable (Self_ID : Task_Id);
 120    pragma Inline (Defer_Abort_Nestable);
 121
 122    procedure Undefer_Abort_Nestable (Self_ID : Task_Id);
 123    pragma Inline (Undefer_Abort_Nestable);
 124
 125    --  NON-INLINE versions without Self_ID for code generated by the
 126    --  expander and for soft links
 127
 128    procedure Defer_Abortion;
 129    procedure Undefer_Abortion;
 130
 131    --  ?????
 132    --  Try to phase out all uses of the above versions.
 133
 134    procedure Do_Pending_Action (Self_ID : Task_Id);
 135    --  Only call with no locks, and when Self_ID.Pending_Action = True
 136    --  Perform necessary pending actions (e.g. abortion, priority change).
 137    --  This procedure is usually called when needed as a result of
 138    --  calling Undefer_Abort, although in the case of e.g. No_Abort
 139    --  restriction, it can be necessary to force execution of pending
 140    --  actions.
 141
 142    function Check_Abort_Status return Integer;
 143    --  Returns Boolean'Pos (True) iff abort signal should raise
 144    --  Standard.Abort_Signal. Only used by IRIX currently.
 145
 146    --------------------------
 147    -- Change Base Priority --
 148    --------------------------
 149
 150    procedure Change_Base_Priority (T : Task_Id);
 151    --  Change the base priority of T.
 152    --  Has to be called with the affected task's ATCB write-locked.
 153    --  May temporariliy release the lock.
 154
 155    procedure Poll_Base_Priority_Change (Self_ID : Task_Id);
 156    --  Has to be called with Self_ID's ATCB write-locked.
 157    --  May temporariliy release the lock.
 158    pragma Inline (Poll_Base_Priority_Change);
 159
 160    ----------------------
 161    -- Task Lock/Unlock --
 162    ----------------------
 163
 164    procedure Task_Lock (Self_ID : Task_Id);
 165    pragma Inline (Task_Lock);
 166
 167    procedure Task_Unlock (Self_ID : Task_Id);
 168    pragma Inline (Task_Unlock);
 169    --  These are versions of Lock_Task and Unlock_Task created for use
 170    --  within the GNARL.
 171
 172    procedure Final_Task_Unlock (Self_ID : Task_Id);
 173    --  This version is only for use in Terminate_Task, when the task
 174    --  is relinquishing further rights to its own ATCB.
 175    --  There is a very interesting potential race condition there, where
 176    --  the old task may run concurrently with a new task that is allocated
 177    --  the old tasks (now reused) ATCB.  The critical thing here is to
 178    --  not make any reference to the ATCB after the lock is released.
 179    --  See also comments on Terminate_Task and Unlock.
 180
 181    procedure Wakeup_Entry_Caller
 182      (Self_ID    : Task_Id;
 183       Entry_Call : Entry_Call_Link;
 184       New_State  : Entry_Call_State);
 185    pragma Inline (Wakeup_Entry_Caller);
 186    --  This is called at the end of service of an entry call,
 187    --  to abort the caller if he is in an abortable part, and
 188    --  to wake up the caller if he is on Entry_Caller_Sleep.
 189    --  Call it holding the lock of Entry_Call.Self.
 190    --
 191    --  Timed_Call or Simple_Call:
 192    --    The caller is waiting on Entry_Caller_Sleep, in
 193    --    Wait_For_Completion, or Wait_For_Completion_With_Timeout.
 194    --
 195    --  Conditional_Call:
 196    --    The caller might be in Wait_For_Completion,
 197    --    waiting for a rendezvous (possibly requeued without abort)
 198    --    to complete.
 199    --
 200    --  Asynchronous_Call:
 201    --    The caller may be executing in the abortable part o
 202    --    an async. select, or on a time delay,
 203    --    if Entry_Call.State >= Was_Abortable.
 204
 205    procedure Locked_Abort_To_Level
 206      (Self_ID : Task_Id;
 207       T       : Task_Id;
 208       L       : ATC_Level);
 209    pragma Inline (Locked_Abort_To_Level);
 210    --  Abort a task to a specified ATC level.
 211    --  Call this only with T locked.
 212
 213 end System.Tasking.Initialization;