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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT RUN-TIME COMPONENTS --
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4 -- --
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5 -- S Y S T E M . A T O M I C _ P R I M I T I V E S --
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6 -- --
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7 -- S p e c --
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8 -- --
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145
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9 -- Copyright (C) 2012-2019, Free Software Foundation, Inc. --
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111
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10 -- --
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11 -- GNAT 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 -- GNAT was originally developed by the GNAT team at New York 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 contains both atomic primitives defined from gcc built-in
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33 -- functions and operations used by the compiler to generate the lock-free
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34 -- implementation of protected objects.
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35
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145
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36 with Interfaces.C;
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37
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111
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38 package System.Atomic_Primitives is
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145
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39 pragma Pure;
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111
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40
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41 type uint is mod 2 ** Long_Integer'Size;
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42
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43 type uint8 is mod 2**8
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44 with Size => 8;
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45
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46 type uint16 is mod 2**16
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47 with Size => 16;
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48
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49 type uint32 is mod 2**32
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50 with Size => 32;
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51
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52 type uint64 is mod 2**64
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53 with Size => 64;
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54
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55 Relaxed : constant := 0;
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56 Consume : constant := 1;
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57 Acquire : constant := 2;
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58 Release : constant := 3;
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59 Acq_Rel : constant := 4;
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60 Seq_Cst : constant := 5;
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61 Last : constant := 6;
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62
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63 subtype Mem_Model is Integer range Relaxed .. Last;
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64
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65 type bool is new Boolean;
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66 pragma Convention (C, bool);
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67
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111
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68 ------------------------------------
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69 -- GCC built-in atomic primitives --
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70 ------------------------------------
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71
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72 function Atomic_Load_8
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73 (Ptr : Address;
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74 Model : Mem_Model := Seq_Cst) return uint8;
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75 pragma Import (Intrinsic, Atomic_Load_8, "__atomic_load_1");
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76
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77 function Atomic_Load_16
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78 (Ptr : Address;
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79 Model : Mem_Model := Seq_Cst) return uint16;
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80 pragma Import (Intrinsic, Atomic_Load_16, "__atomic_load_2");
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81
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82 function Atomic_Load_32
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83 (Ptr : Address;
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84 Model : Mem_Model := Seq_Cst) return uint32;
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85 pragma Import (Intrinsic, Atomic_Load_32, "__atomic_load_4");
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86
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87 function Atomic_Load_64
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88 (Ptr : Address;
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89 Model : Mem_Model := Seq_Cst) return uint64;
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90 pragma Import (Intrinsic, Atomic_Load_64, "__atomic_load_8");
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91
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92 function Sync_Compare_And_Swap_8
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93 (Ptr : Address;
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94 Expected : uint8;
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95 Desired : uint8) return uint8;
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96 pragma Import (Intrinsic,
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97 Sync_Compare_And_Swap_8,
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98 "__sync_val_compare_and_swap_1");
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99
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100 function Sync_Compare_And_Swap_16
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101 (Ptr : Address;
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102 Expected : uint16;
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103 Desired : uint16) return uint16;
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104 pragma Import (Intrinsic,
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105 Sync_Compare_And_Swap_16,
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106 "__sync_val_compare_and_swap_2");
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107
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108 function Sync_Compare_And_Swap_32
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109 (Ptr : Address;
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110 Expected : uint32;
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111 Desired : uint32) return uint32;
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112 pragma Import (Intrinsic,
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113 Sync_Compare_And_Swap_32,
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114 "__sync_val_compare_and_swap_4");
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115
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116 function Sync_Compare_And_Swap_64
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117 (Ptr : Address;
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118 Expected : uint64;
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119 Desired : uint64) return uint64;
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120 pragma Import (Intrinsic,
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121 Sync_Compare_And_Swap_64,
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122 "__sync_val_compare_and_swap_8");
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123
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131
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124 -- ??? We might want to switch to the __atomic series of builtins for
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125 -- compare-and-swap operations at some point.
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126
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127 -- function Atomic_Compare_Exchange_8
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128 -- (Ptr : Address;
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129 -- Expected : Address;
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130 -- Desired : uint8;
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131 -- Weak : Boolean := False;
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132 -- Success_Model : Mem_Model := Seq_Cst;
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133 -- Failure_Model : Mem_Model := Seq_Cst) return Boolean;
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134 -- pragma Import (Intrinsic,
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135 -- Atomic_Compare_Exchange_8,
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136 -- "__atomic_compare_exchange_1");
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137
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145
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138 function Atomic_Test_And_Set
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139 (Ptr : System.Address;
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140 Model : Mem_Model := Seq_Cst) return bool;
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141 pragma Import (Intrinsic, Atomic_Test_And_Set, "__atomic_test_and_set");
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142
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143 procedure Atomic_Clear
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144 (Ptr : System.Address;
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145 Model : Mem_Model := Seq_Cst);
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146 pragma Import (Intrinsic, Atomic_Clear, "__atomic_clear");
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147
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148 function Atomic_Always_Lock_Free
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149 (Size : Interfaces.C.size_t;
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150 Ptr : System.Address := System.Null_Address) return bool;
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151 pragma Import
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152 (Intrinsic, Atomic_Always_Lock_Free, "__atomic_always_lock_free");
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153
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154 --------------------------
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155 -- Lock-free operations --
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156 --------------------------
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157
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158 -- The lock-free implementation uses two atomic instructions for the
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159 -- expansion of protected operations:
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160
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161 -- * Lock_Free_Read_N atomically loads the value of the protected component
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162 -- accessed by the current protected operation.
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163
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164 -- * Lock_Free_Try_Write_N tries to write the Desired value into Ptr only
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165 -- if Expected and Desired mismatch.
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166
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167 function Lock_Free_Read_8 (Ptr : Address) return uint8;
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168
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169 function Lock_Free_Read_16 (Ptr : Address) return uint16;
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170
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171 function Lock_Free_Read_32 (Ptr : Address) return uint32;
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172
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173 function Lock_Free_Read_64 (Ptr : Address) return uint64;
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174
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175 function Lock_Free_Try_Write_8
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176 (Ptr : Address;
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177 Expected : in out uint8;
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178 Desired : uint8) return Boolean;
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179
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180 function Lock_Free_Try_Write_16
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181 (Ptr : Address;
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182 Expected : in out uint16;
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183 Desired : uint16) return Boolean;
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184
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185 function Lock_Free_Try_Write_32
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186 (Ptr : Address;
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187 Expected : in out uint32;
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188 Desired : uint32) return Boolean;
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189
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190 function Lock_Free_Try_Write_64
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191 (Ptr : Address;
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192 Expected : in out uint64;
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193 Desired : uint64) return Boolean;
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194
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195 pragma Inline (Lock_Free_Read_8);
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196 pragma Inline (Lock_Free_Read_16);
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197 pragma Inline (Lock_Free_Read_32);
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198 pragma Inline (Lock_Free_Read_64);
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199 pragma Inline (Lock_Free_Try_Write_8);
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200 pragma Inline (Lock_Free_Try_Write_16);
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201 pragma Inline (Lock_Free_Try_Write_32);
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202 pragma Inline (Lock_Free_Try_Write_64);
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203 end System.Atomic_Primitives;
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