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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
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4 -- --
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5 -- A D A . D Y N A M I C _ P R I O R I T I E S --
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6 -- --
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7 -- B o d y --
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8 -- --
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131
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9 -- Copyright (C) 1992-2018, Free Software Foundation, Inc. --
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111
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10 -- --
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11 -- GNARL is free software; you can redistribute it and/or modify it under --
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12 -- terms of the GNU General Public License as published by the Free Soft- --
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13 -- ware Foundation; either version 3, or (at your option) any later ver- --
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14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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16 -- or FITNESS FOR A PARTICULAR PURPOSE. --
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17 -- --
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18 -- As a special exception under Section 7 of GPL version 3, you are granted --
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19 -- additional permissions described in the GCC Runtime Library Exception, --
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20 -- version 3.1, as published by the Free Software Foundation. --
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21 -- --
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22 -- You should have received a copy of the GNU General Public License and --
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23 -- a copy of the GCC Runtime Library Exception along with this program; --
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24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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25 -- <http://www.gnu.org/licenses/>. --
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26 -- --
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27 -- GNARL was developed by the GNARL team at Florida State University. --
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28 -- Extensive contributions were provided by Ada Core Technologies, Inc. --
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29 -- --
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30 ------------------------------------------------------------------------------
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31
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32 with System.Task_Primitives.Operations;
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33 with System.Tasking;
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34 with System.Parameters;
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35 with System.Soft_Links;
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36
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37 with Ada.Unchecked_Conversion;
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38
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39 package body Ada.Dynamic_Priorities is
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40
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41 package STPO renames System.Task_Primitives.Operations;
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42 package SSL renames System.Soft_Links;
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43
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44 use System.Parameters;
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45 use System.Tasking;
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46
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47 function Convert_Ids is new
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48 Ada.Unchecked_Conversion
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49 (Task_Identification.Task_Id, System.Tasking.Task_Id);
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50
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51 ------------------
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52 -- Get_Priority --
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53 ------------------
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54
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55 -- Inquire base priority of a task
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56
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57 function Get_Priority
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58 (T : Ada.Task_Identification.Task_Id :=
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59 Ada.Task_Identification.Current_Task) return System.Any_Priority
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60 is
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61 Target : constant Task_Id := Convert_Ids (T);
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62 Error_Message : constant String := "Trying to get the priority of a ";
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63
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64 begin
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65 if Target = Convert_Ids (Ada.Task_Identification.Null_Task_Id) then
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66 raise Program_Error with Error_Message & "null task";
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67 end if;
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68
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69 if Task_Identification.Is_Terminated (T) then
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70 raise Tasking_Error with Error_Message & "terminated task";
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71 end if;
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72
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73 return Target.Common.Base_Priority;
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74 end Get_Priority;
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75
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76 ------------------
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77 -- Set_Priority --
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78 ------------------
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79
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80 -- Change base priority of a task dynamically
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81
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82 procedure Set_Priority
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83 (Priority : System.Any_Priority;
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84 T : Ada.Task_Identification.Task_Id :=
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85 Ada.Task_Identification.Current_Task)
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86 is
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87 Target : constant Task_Id := Convert_Ids (T);
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88 Error_Message : constant String := "Trying to set the priority of a ";
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89 Yield_Needed : Boolean;
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90
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91 begin
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92 if Target = Convert_Ids (Ada.Task_Identification.Null_Task_Id) then
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93 raise Program_Error with Error_Message & "null task";
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94 end if;
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95
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96 -- Setting the priority of an already-terminated task doesn't do
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97 -- anything (see RM-D.5.1(7)). Note that Get_Priority is different in
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98 -- this regard.
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99
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100 if Task_Identification.Is_Terminated (T) then
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101 return;
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102 end if;
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103
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104 SSL.Abort_Defer.all;
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105
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106 if Single_Lock then
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107 STPO.Lock_RTS;
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108 end if;
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109
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110 STPO.Write_Lock (Target);
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111
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112 Target.Common.Base_Priority := Priority;
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113
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114 if Target.Common.Call /= null
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115 and then
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116 Target.Common.Call.Acceptor_Prev_Priority /= Priority_Not_Boosted
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117 then
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118 -- Target is within a rendezvous, so ensure the correct priority
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119 -- will be reset when finishing the rendezvous, and only change the
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120 -- priority immediately if the new priority is greater than the
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121 -- current (inherited) priority.
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122
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123 Target.Common.Call.Acceptor_Prev_Priority := Priority;
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124
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125 if Priority >= Target.Common.Current_Priority then
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126 Yield_Needed := True;
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127 STPO.Set_Priority (Target, Priority);
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128 else
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129 Yield_Needed := False;
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130 end if;
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131
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132 else
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133 Yield_Needed := True;
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134 STPO.Set_Priority (Target, Priority);
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135
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136 if Target.Common.State = Entry_Caller_Sleep then
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137 Target.Pending_Priority_Change := True;
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138 STPO.Wakeup (Target, Target.Common.State);
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139 end if;
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140 end if;
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141
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142 STPO.Unlock (Target);
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143
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144 if Single_Lock then
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145 STPO.Unlock_RTS;
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146 end if;
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147
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148 if STPO.Self = Target and then Yield_Needed then
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149
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150 -- Yield is needed to enforce FIFO task dispatching
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151
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152 -- LL Set_Priority is made while holding the RTS lock so that it is
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153 -- inheriting high priority until it release all the RTS locks.
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154
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155 -- If this is used in a system where Ceiling Locking is not enforced
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156 -- we may end up getting two Yield effects.
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157
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158 STPO.Yield;
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159 end if;
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160
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161 SSL.Abort_Undefer.all;
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162 end Set_Priority;
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163
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164 end Ada.Dynamic_Priorities;
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