gcc/ada/a-dynpri.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                 GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS              --
   4 --                                                                          --
   5 --                 A D A . D Y N A M I C _ P R I O R I T I E S              --
   6 --                                                                          --
   7 --                                  B o d y                                 --
   8 --                                                                          --
   9 --                                                                          --
  10 --          Copyright (C) 1992-2001, Free Software Foundation, Inc.         --
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  13 -- terms of the  GNU General Public License as published  by the Free Soft- --
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  15 -- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
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  17 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
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  21 -- MA 02111-1307, USA.                                                      --
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  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 with Ada.Task_Identification;
  36 --  used for Task_Id
  37 --           Current_Task
  38 --           Null_Task_Id
  39 --           Is_Terminated
  40
  41 with System.Task_Primitives.Operations;
  42 --  used for Write_Lock
  43 --           Unlock
  44 --           Set_Priority
  45 --           Wakeup
  46 --           Self
  47
  48 with System.Tasking;
  49 --  used for Task_ID
  50
  51 with Ada.Exceptions;
  52 --  used for Raise_Exception
  53
  54 with System.Tasking.Initialization;
  55 --  used for Defer/Undefer_Abort
  56
  57 with System.Parameters;
  58 --  used for Single_Lock
  59
  60 with Unchecked_Conversion;
  61
  62 package body Ada.Dynamic_Priorities is
  63
  64    package STPO renames System.Task_Primitives.Operations;
  65
  66    use System.Parameters;
  67    use System.Tasking;
  68    use Ada.Exceptions;
  69
  70    function Convert_Ids is new
  71      Unchecked_Conversion
  72        (Task_Identification.Task_Id, System.Tasking.Task_ID);
  73
  74    ------------------
  75    -- Get_Priority --
  76    ------------------
  77
  78    --  Inquire base priority of a task
  79
  80    function Get_Priority
  81      (T : Ada.Task_Identification.Task_Id :=
  82           Ada.Task_Identification.Current_Task)
  83       return System.Any_Priority is
  84
  85       Target : constant Task_ID := Convert_Ids (T);
  86       Error_Message : constant String := "Trying to get the priority of a ";
  87
  88    begin
  89       if Target = Convert_Ids (Ada.Task_Identification.Null_Task_Id) then
  90          Raise_Exception (Program_Error'Identity,
  91            Error_Message & "null task");
  92       end if;
  93
  94       if Task_Identification.Is_Terminated (T) then
  95          Raise_Exception (Tasking_Error'Identity,
  96            Error_Message & "null task");
  97       end if;
  98
  99       return Target.Common.Base_Priority;
 100    end Get_Priority;
 101
 102    ------------------
 103    -- Set_Priority --
 104    ------------------
 105
 106    --  Change base priority of a task dynamically
 107
 108    procedure Set_Priority
 109      (Priority : System.Any_Priority;
 110       T : Ada.Task_Identification.Task_Id :=
 111           Ada.Task_Identification.Current_Task)
 112    is
 113       Target  : constant Task_ID := Convert_Ids (T);
 114       Self_ID : constant Task_ID := STPO.Self;
 115       Error_Message : constant String := "Trying to set the priority of a ";
 116
 117    begin
 118       if Target = Convert_Ids (Ada.Task_Identification.Null_Task_Id) then
 119          Raise_Exception (Program_Error'Identity,
 120            Error_Message & "null task");
 121       end if;
 122
 123       if Task_Identification.Is_Terminated (T) then
 124          Raise_Exception (Tasking_Error'Identity,
 125            Error_Message & "terminated task");
 126       end if;
 127
 128       Initialization.Defer_Abort (Self_ID);
 129
 130       if Single_Lock then
 131          STPO.Lock_RTS;
 132       end if;
 133
 134       STPO.Write_Lock (Target);
 135
 136       if Self_ID = Target then
 137          Target.Common.Base_Priority := Priority;
 138          STPO.Set_Priority (Target, Priority);
 139
 140          STPO.Unlock (Target);
 141
 142          if Single_Lock then
 143             STPO.Unlock_RTS;
 144          end if;
 145
 146          STPO.Yield;
 147          --  Yield is needed to enforce FIFO task dispatching.
 148          --  LL Set_Priority is made while holding the RTS lock so that
 149          --  it is inheriting high priority until it release all the RTS
 150          --  locks.
 151          --  If this is used in a system where Ceiling Locking is
 152          --  not enforced we may end up getting two Yield effects.
 153
 154       else
 155          Target.New_Base_Priority := Priority;
 156          Target.Pending_Priority_Change := True;
 157          Target.Pending_Action := True;
 158
 159          STPO.Wakeup (Target, Target.Common.State);
 160          --  If the task is suspended, wake it up to perform the change.
 161          --  check for ceiling violations ???
 162
 163          STPO.Unlock (Target);
 164
 165          if Single_Lock then
 166             STPO.Unlock_RTS;
 167          end if;
 168       end if;
 169
 170       Initialization.Undefer_Abort (Self_ID);
 171    end Set_Priority;
 172
 173 end Ada.Dynamic_Priorities;