gcc/ada/s-taspri-os2.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                  GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                --
   4 --                                                                          --
   5 --                S Y S T E M . T A S K _ P R I M I T I V E S               --
   6 --                                                                          --
   7 --                                  S p e c                                 --
   8 --                                                                          --
   9 --             Copyright (C) 1991-1994, Florida State University            --
  10 --                     Copyright (C) 1995-2005, AdaCore                     --
  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,  51  Franklin  Street,  Fifth  Floor, --
  21 -- Boston, MA 02110-1301, 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.       --
  31 -- Extensive contributions were provided by Ada Core Technologies, Inc.     --
  32 --                                                                          --
  33 ------------------------------------------------------------------------------
  34
  35 --  This is an OS/2 version of this package
  36
  37 --  This package provides low-level support for most tasking features
  38
  39 pragma Polling (Off);
  40 --  Turn off polling, we do not want ATC polling to take place during
  41 --  tasking operations. It causes infinite loops and other problems.
  42
  43 with Interfaces.OS2Lib.Threads;
  44 with Interfaces.OS2Lib.Synchronization;
  45
  46 package System.Task_Primitives is
  47    pragma Preelaborate;
  48
  49    type Lock is limited private;
  50    --  Should be used for implementation of protected objects.
  51
  52    type RTS_Lock is limited private;
  53    --  Should be used inside the runtime system.
  54    --  The difference between Lock and the RTS_Lock is that the later
  55    --  one serves only as a semaphore so that do not check for
  56    --  ceiling violations.
  57
  58    type Task_Body_Access is access procedure;
  59    --  Pointer to the task body's entry point (or possibly a wrapper
  60    --  declared local to the GNARL).
  61
  62    type Private_Data is limited private;
  63    --  Any information that the GNULLI needs maintained on a per-task
  64    --  basis.  A component of this type is guaranteed to be included
  65    --  in the Ada_Task_Control_Block.
  66
  67 private
  68
  69    type Lock is record
  70       Mutex          : aliased Interfaces.OS2Lib.Synchronization.HMTX;
  71       Priority       : Integer;
  72       Owner_Priority : Integer;
  73       Owner_ID       : Address;
  74    end record;
  75
  76    type RTS_Lock is new Lock;
  77
  78    type Suspension_Object is record
  79       State : Boolean;
  80       pragma Atomic (State);
  81       --  Boolean that indicates whether the object is open. This field is
  82       --  marked Atomic to ensure that we can read its value without locking
  83       --  the access to the Suspension_Object.
  84
  85       Waiting : Boolean;
  86       --  Flag showing if there is a task already suspended on this object
  87
  88       L : aliased Interfaces.OS2Lib.Synchronization.HMTX;
  89       --  Protection for ensuring mutual exclusion on the Suspension_Object
  90
  91       CV : aliased Interfaces.OS2Lib.Synchronization.HEV;
  92       --  Condition variable used to queue threads until condition is signaled
  93    end record;
  94
  95    type Private_Data is record
  96       Thread : aliased Interfaces.OS2Lib.Threads.TID;
  97       pragma Atomic (Thread);
  98       --  Thread field may be updated by two different threads of control.
  99       --  (See, Enter_Task and Create_Task in s-taprop.adb). They put the same
 100       --  value (thr_self value). We do not want to use lock on those
 101       --  operations and the only thing we have to make sure is that they are
 102       --  updated in atomic fashion.
 103
 104       CV : aliased Interfaces.OS2Lib.Synchronization.HEV;
 105
 106       L  : aliased RTS_Lock;
 107       --  Protection for all components is lock L
 108
 109       Current_Priority : Integer := -1;
 110       --  The Current_Priority is the actual priority of a thread. This field
 111       --  is needed because it is only possible to set delta priority in OS/2.
 112       --  The only places where this field should be set are Set_Priority,
 113       --  Create_Task and Initialize (Environment).
 114
 115       Wrapper : Interfaces.OS2Lib.Threads.PFNTHREAD;
 116       --  This is the original wrapper passed by Operations.Create_Task. When
 117       --  installing an exception handler in a thread, the thread starts
 118       --  executing the Exception_Wrapper which calls Wrapper when the handler
 119       --  has been installed. The handler is removed when wrapper returns.
 120    end record;
 121
 122 end System.Task_Primitives;