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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 -- S Y S T E M . T A S K I N G . P R O T E C T E D _ O B J E C T S --
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6 -- --
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7 -- S p e c --
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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 -- This package provides necessary definitions to handle simple (i.e without
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33 -- entries) protected objects.
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34
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35 -- All the routines that handle protected objects with entries have been moved
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36 -- to two children: Entries and Operations. Note that Entries only contains
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37 -- the type declaration and the OO primitives. This is needed to avoid
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38 -- circular dependency.
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39
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40 -- This package is part of the high level tasking interface used by the
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41 -- compiler to expand Ada 95 tasking constructs into simpler run time calls
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42 -- (aka GNARLI, GNU Ada Run-time Library Interface)
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43
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44 -- Note: the compiler generates direct calls to this interface, via Rtsfind.
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45 -- Any changes to this interface may require corresponding compiler changes
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46 -- in exp_ch9.adb and possibly exp_ch7.adb and exp_attr.adb
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47
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48 package System.Tasking.Protected_Objects is
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49 pragma Elaborate_Body;
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50
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51 ---------------------------------
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52 -- Compiler Interface (GNARLI) --
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53 ---------------------------------
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54
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55 -- The compiler will expand in the GNAT tree the following construct:
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56
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57 -- protected PO is
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58 -- procedure P;
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59 -- private
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60 -- open : boolean := false;
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61 -- end PO;
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62
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63 -- protected body PO is
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64 -- procedure P is
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65 -- ...variable declarations...
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66 -- begin
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67 -- ...B...
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68 -- end P;
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69 -- end PO;
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70
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71 -- as follows:
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72
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73 -- protected type poT is
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74 -- procedure p;
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75 -- private
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76 -- open : boolean := false;
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77 -- end poT;
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78 -- type poTV is limited record
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79 -- open : boolean := false;
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80 -- _object : aliased protection;
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81 -- end record;
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82 -- procedure poPT__pN (_object : in out poTV);
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83 -- procedure poPT__pP (_object : in out poTV);
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84 -- freeze poTV [
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85 -- procedure poTVI (_init : in out poTV) is
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86 -- begin
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87 -- _init.open := false;
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88 -- object-init-proc (_init._object);
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89 -- initialize_protection (_init._object'unchecked_access,
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90 -- unspecified_priority);
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91 -- return;
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92 -- end _init_proc;
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93 -- ]
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94 -- po : poT;
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95 -- poTVI (poTV!(po));
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96
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97 -- procedure poPT__pN (_object : in out poTV) is
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98 -- poR : protection renames _object._object;
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99 -- openP : boolean renames _object.open;
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100 -- ...variable declarations...
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101 -- begin
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102 -- ...B...
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103 -- return;
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104 -- end poPT__pN;
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105
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106 -- procedure poPT__pP (_object : in out poTV) is
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107 -- procedure _clean is
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108 -- begin
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109 -- unlock (_object._object'unchecked_access);
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110 -- return;
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111 -- end _clean;
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112 -- begin
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113 -- lock (_object._object'unchecked_access);
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114 -- B2b : begin
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115 -- poPT__pN (_object);
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116 -- at end
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117 -- _clean;
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118 -- end B2b;
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119 -- return;
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120 -- end poPT__pP;
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121
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122 Null_Protected_Entry : constant := Null_Entry;
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123
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124 Max_Protected_Entry : constant := Max_Entry;
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125
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126 type Protected_Entry_Index is new Entry_Index
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127 range Null_Protected_Entry .. Max_Protected_Entry;
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128
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129 type Barrier_Function_Pointer is access
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130 function
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131 (O : System.Address;
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132 E : Protected_Entry_Index)
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133 return Boolean;
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134 -- Pointer to a function which evaluates the barrier of a protected
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135 -- entry body. O is a pointer to the compiler-generated record
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136 -- representing the protected object, and E is the index of the
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137 -- entry serviced by the body.
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138
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139 type Entry_Action_Pointer is access
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140 procedure
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141 (O : System.Address;
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142 P : System.Address;
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143 E : Protected_Entry_Index);
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144 -- Pointer to a procedure which executes the sequence of statements
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145 -- of a protected entry body. O is a pointer to the compiler-generated
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146 -- record representing the protected object, P is a pointer to the
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147 -- record of entry parameters, and E is the index of the
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148 -- entry serviced by the body.
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149
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150 type Entry_Body is record
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151 Barrier : Barrier_Function_Pointer;
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152 Action : Entry_Action_Pointer;
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153 end record;
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154 -- The compiler-generated code passes objects of this type to the GNARL
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155 -- to allow it to access the executable code of an entry body and its
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156 -- barrier.
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157
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158 type Protection is limited private;
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159 -- This type contains the GNARL state of a protected object. The
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160 -- application-defined portion of the state (i.e. private objects)
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161 -- is maintained by the compiler-generated code.
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162 -- Note that there are now 2 Protection types. One for the simple
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163 -- case (no entries) and one for the general case that needs the whole
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164 -- Finalization mechanism.
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165 -- This split helps in the case of restricted run time where we want to
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166 -- minimize the size of the code.
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167
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168 type Protection_Access is access all Protection;
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169
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170 Null_PO : constant Protection_Access := null;
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171
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172 function Get_Ceiling
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173 (Object : Protection_Access) return System.Any_Priority;
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174 -- Returns the new ceiling priority of the protected object
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175
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176 procedure Initialize_Protection
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177 (Object : Protection_Access;
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178 Ceiling_Priority : Integer);
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179 -- Initialize the Object parameter so that it can be used by the runtime
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180 -- to keep track of the runtime state of a protected object.
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181
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182 procedure Lock (Object : Protection_Access);
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183 -- Lock a protected object for write access. Upon return, the caller
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184 -- owns the lock to this object, and no other call to Lock or
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185 -- Lock_Read_Only with the same argument will return until the
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186 -- corresponding call to Unlock has been made by the caller.
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187
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188 procedure Lock_Read_Only (Object : Protection_Access);
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189 -- Lock a protected object for read access. Upon return, the caller
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190 -- owns the lock for read access, and no other calls to Lock with the
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191 -- same argument will return until the corresponding call to Unlock
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192 -- has been made by the caller. Other calls to Lock_Read_Only may (but
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193 -- need not) return before the call to Unlock, and the corresponding
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194 -- callers will also own the lock for read access.
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195
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196 procedure Set_Ceiling
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197 (Object : Protection_Access;
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198 Prio : System.Any_Priority);
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199 -- Sets the new ceiling priority of the protected object
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200
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201 procedure Unlock (Object : Protection_Access);
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202 -- Relinquish ownership of the lock for the object represented by
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203 -- the Object parameter. If this ownership was for write access, or
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204 -- if it was for read access where there are no other read access
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205 -- locks outstanding, one (or more, in the case of Lock_Read_Only)
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206 -- of the tasks waiting on this lock (if any) will be given the
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207 -- lock and allowed to return from the Lock or Lock_Read_Only call.
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208
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209 private
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210 type Protection is record
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211 L : aliased Task_Primitives.Lock;
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212 -- Lock used to ensure mutual exclusive access to the protected object
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213
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214 Ceiling : System.Any_Priority;
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215 -- Ceiling priority associated to the protected object
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216
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217 New_Ceiling : System.Any_Priority;
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218 -- New ceiling priority associated to the protected object. In case
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219 -- of assignment of a new ceiling priority to the protected object the
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220 -- frontend generates a call to set_ceiling to save the new value in
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221 -- this field. After such assignment this value can be read by means
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222 -- of the 'Priority attribute, which generates a call to get_ceiling.
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223 -- However, the ceiling of the protected object will not be changed
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224 -- until completion of the protected action in which the assignment
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225 -- has been executed (AARM D.5.2 (10/2)).
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226
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227 Owner : Task_Id;
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228 -- This field contains the protected object's owner. Null_Task
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229 -- indicates that the protected object is not currently being used.
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230 -- This information is used for detecting the type of potentially
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231 -- blocking operations described in the ARM 9.5.1, par. 15 (external
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232 -- calls on a protected subprogram with the same target object as that
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233 -- of the protected action).
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234 end record;
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235
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236 procedure Finalize_Protection (Object : in out Protection);
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237 -- Clean up a Protection object (in particular, finalize the associated
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238 -- Lock object). The compiler generates calls automatically to this
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239 -- procedure
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240
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241 end System.Tasking.Protected_Objects;
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