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1 /* Copyright (C) 2008-2017 Free Software Foundation, Inc.
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2 Contributed by Richard Henderson <rth@redhat.com>.
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3
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4 This file is part of the GNU Transactional Memory Library (libitm).
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5
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6 Libitm is free software; you can redistribute it and/or modify it
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7 under the terms of the GNU General Public License as published by
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8 the Free Software Foundation; either version 3 of the License, or
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9 (at your option) any later version.
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10
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11 Libitm is distributed in the hope that it will be useful, but WITHOUT ANY
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12 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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13 FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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14 more details.
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15
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16 Under Section 7 of GPL version 3, you are granted additional
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17 permissions described in the GCC Runtime Library Exception, version
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18 3.1, as published by the Free Software Foundation.
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19
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20 You should have received a copy of the GNU General Public License and
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21 a copy of the GCC Runtime Library Exception along with this program;
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22 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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23 <http://www.gnu.org/licenses/>. */
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24
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25 #include "libitm_i.h"
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26
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27 // Avoid a dependency on libstdc++ for the pure virtuals in abi_dispatch.
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28 extern "C" void HIDDEN
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29 __cxa_pure_virtual ()
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30 {
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31 abort ();
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32 }
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33
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34 using namespace GTM;
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35
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36 namespace {
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37
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38 // This group consists of the serial, serialirr, and serialirr_onwrite
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39 // methods, which all need no global state (except what is already provided
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40 // by the serial mode implementation).
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41 struct serial_mg : public method_group
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42 {
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43 virtual void init() { }
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44 virtual void fini() { }
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45 };
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46
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47 static serial_mg o_serial_mg;
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48
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49
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50 class serialirr_dispatch : public abi_dispatch
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51 {
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52 public:
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53 serialirr_dispatch() : abi_dispatch(false, true, true, false,
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54 gtm_thread::STATE_SERIAL | gtm_thread::STATE_IRREVOCABLE, &o_serial_mg)
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55 { }
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56
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57 protected:
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58 serialirr_dispatch(bool ro, bool wt, bool uninstrumented,
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59 bool closed_nesting, uint32_t requires_serial, method_group* mg) :
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60 abi_dispatch(ro, wt, uninstrumented, closed_nesting, requires_serial, mg)
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61 { }
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62
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63 // Transactional loads and stores simply access memory directly.
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64 // These methods are static to avoid indirect calls, and will be used by the
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65 // virtual ABI dispatch methods or by static direct-access methods created
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66 // below.
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67 template <typename V> static V load(const V* addr, ls_modifier mod)
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68 {
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69 return *addr;
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70 }
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71 template <typename V> static void store(V* addr, const V value,
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72 ls_modifier mod)
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73 {
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74 *addr = value;
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75 }
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76
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77 public:
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78 static void memtransfer_static(void *dst, const void* src, size_t size,
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79 bool may_overlap, ls_modifier dst_mod, ls_modifier src_mod)
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80 {
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81 if (!may_overlap)
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82 ::memcpy(dst, src, size);
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83 else
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84 ::memmove(dst, src, size);
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85 }
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86
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87 static void memset_static(void *dst, int c, size_t size, ls_modifier mod)
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88 {
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89 ::memset(dst, c, size);
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90 }
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91
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92 CREATE_DISPATCH_METHODS(virtual, )
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93 CREATE_DISPATCH_METHODS_MEM()
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94
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95 virtual gtm_restart_reason begin_or_restart() { return NO_RESTART; }
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96 virtual bool trycommit(gtm_word& priv_time) { return true; }
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97 virtual void rollback(gtm_transaction_cp *cp) { abort(); }
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98 virtual bool snapshot_most_recent() { return true; }
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99
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100 virtual abi_dispatch* closed_nesting_alternative()
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101 {
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102 // For nested transactions with an instrumented code path, we can do
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103 // undo logging.
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104 return GTM::dispatch_serial();
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105 }
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106 };
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107
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108 class serial_dispatch : public abi_dispatch
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109 {
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110 protected:
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111 static void log(const void *addr, size_t len)
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112 {
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113 gtm_thread *tx = gtm_thr();
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114 tx->undolog.log(addr, len);
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115 }
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116
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117 template <typename V> static V load(const V* addr, ls_modifier mod)
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118 {
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119 return *addr;
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120 }
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121 template <typename V> static void store(V* addr, const V value,
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122 ls_modifier mod)
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123 {
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124 if (mod != WaW)
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125 log(addr, sizeof(V));
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126 *addr = value;
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127 }
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128
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129 public:
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130 static void memtransfer_static(void *dst, const void* src, size_t size,
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131 bool may_overlap, ls_modifier dst_mod, ls_modifier src_mod)
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132 {
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133 if (dst_mod != WaW && dst_mod != NONTXNAL)
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134 log(dst, size);
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135 if (!may_overlap)
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136 ::memcpy(dst, src, size);
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137 else
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138 ::memmove(dst, src, size);
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139 }
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140
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141 static void memset_static(void *dst, int c, size_t size, ls_modifier mod)
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142 {
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143 if (mod != WaW)
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144 log(dst, size);
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145 ::memset(dst, c, size);
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146 }
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147
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148 virtual gtm_restart_reason begin_or_restart() { return NO_RESTART; }
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149 virtual bool trycommit(gtm_word& priv_time) { return true; }
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150 // Local undo will handle this.
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151 // trydropreference() need not be changed either.
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152 virtual void rollback(gtm_transaction_cp *cp) { }
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153 virtual bool snapshot_most_recent() { return true; }
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154
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155 CREATE_DISPATCH_METHODS(virtual, )
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156 CREATE_DISPATCH_METHODS_MEM()
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157
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158 serial_dispatch() : abi_dispatch(false, true, false, true,
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159 gtm_thread::STATE_SERIAL, &o_serial_mg)
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160 { }
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161 };
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162
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163
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164 // Like serialirr_dispatch but does not requests serial-irrevocable mode until
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165 // the first write in the transaction. Can be useful for read-mostly workloads
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166 // and testing, but is likely too simple to be of general purpose.
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167 class serialirr_onwrite_dispatch : public serialirr_dispatch
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168 {
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169 public:
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170 serialirr_onwrite_dispatch() :
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171 serialirr_dispatch(false, true, false, false, 0, &o_serial_mg) { }
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172
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173 protected:
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174 static void pre_write()
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175 {
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176 gtm_thread *tx = gtm_thr();
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177 if (!(tx->state & (gtm_thread::STATE_SERIAL
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178 | gtm_thread::STATE_IRREVOCABLE)))
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179 tx->serialirr_mode();
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180 }
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181
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182 // Transactional loads access memory directly.
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183 // Transactional stores switch to serial mode first.
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184 template <typename V> static void store(V* addr, const V value,
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185 ls_modifier mod)
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186 {
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187 pre_write();
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188 serialirr_dispatch::store(addr, value, mod);
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189 }
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190
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191 public:
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192 static void memtransfer_static(void *dst, const void* src, size_t size,
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193 bool may_overlap, ls_modifier dst_mod, ls_modifier src_mod)
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194 {
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195 pre_write();
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196 serialirr_dispatch::memtransfer_static(dst, src, size, may_overlap,
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197 dst_mod, src_mod);
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198 }
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199
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200 static void memset_static(void *dst, int c, size_t size, ls_modifier mod)
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201 {
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202 pre_write();
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203 serialirr_dispatch::memset_static(dst, c, size, mod);
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204 }
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205
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206 CREATE_DISPATCH_METHODS(virtual, )
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207 CREATE_DISPATCH_METHODS_MEM()
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208
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209 virtual void rollback(gtm_transaction_cp *cp)
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210 {
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211 gtm_thread *tx = gtm_thr();
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212 if (tx->state & gtm_thread::STATE_IRREVOCABLE)
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213 abort();
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214 }
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215
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216 virtual bool snapshot_most_recent() { return true; }
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217 };
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218
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219 // This group is pure HTM with serial mode as a fallback. There is no
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220 // difference to serial_mg except that we need to enable or disable the HTM
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221 // fastpath. See gtm_thread::begin_transaction.
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222 struct htm_mg : public method_group
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223 {
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224 virtual void init()
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225 {
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226 // Enable the HTM fastpath if the HW is available. The fastpath is
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227 // initially disabled.
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228 #ifdef USE_HTM_FASTPATH
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229 gtm_thread::serial_lock.set_htm_fastpath(htm_init());
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230 #endif
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231 }
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232 virtual void fini()
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233 {
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234 // Disable the HTM fastpath.
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235 gtm_thread::serial_lock.set_htm_fastpath(0);
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236 }
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237 };
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238
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239 static htm_mg o_htm_mg;
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240
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241 // We just need the subclass to associate it with the HTM method group that
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242 // sets up the HTM fast path. This will use serial_dispatch as fallback for
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243 // transactions that might get canceled; it has a different method group, but
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244 // this is harmless for serial dispatchs because they never abort.
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245 class htm_dispatch : public serialirr_dispatch
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246 {
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247 public:
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248 htm_dispatch() : serialirr_dispatch(false, true, false, false,
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249 gtm_thread::STATE_SERIAL | gtm_thread::STATE_IRREVOCABLE, &o_htm_mg)
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250 { }
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251 };
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252
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253 } // anon namespace
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254
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255 static const serialirr_dispatch o_serialirr_dispatch;
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256 static const serial_dispatch o_serial_dispatch;
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257 static const serialirr_onwrite_dispatch o_serialirr_onwrite_dispatch;
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258 static const htm_dispatch o_htm_dispatch;
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259
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260 abi_dispatch *
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261 GTM::dispatch_serialirr ()
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262 {
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263 return const_cast<serialirr_dispatch *>(&o_serialirr_dispatch);
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264 }
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265
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266 abi_dispatch *
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267 GTM::dispatch_serial ()
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268 {
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269 return const_cast<serial_dispatch *>(&o_serial_dispatch);
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270 }
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271
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272 abi_dispatch *
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273 GTM::dispatch_serialirr_onwrite ()
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274 {
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275 return
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276 const_cast<serialirr_onwrite_dispatch *>(&o_serialirr_onwrite_dispatch);
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277 }
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278
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279 abi_dispatch *
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280 GTM::dispatch_htm ()
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281 {
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282 return const_cast<htm_dispatch *>(&o_htm_dispatch);
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283 }
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284
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285 // Put the transaction into serial-irrevocable mode.
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286
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287 void
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288 GTM::gtm_thread::serialirr_mode ()
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289 {
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290 struct abi_dispatch *disp = abi_disp ();
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291
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292 #if defined(USE_HTM_FASTPATH)
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293 // HTM fastpath. If we are executing a HW transaction, don't go serial but
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294 // continue. See gtm_thread::begin_transaction.
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295 if (likely(!gtm_thread::serial_lock.htm_fastpath_disabled()))
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296 return;
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297 #endif
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298
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299 if (this->state & STATE_SERIAL)
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300 {
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301 if (this->state & STATE_IRREVOCABLE)
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302 return;
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303
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304 // Try to commit the dispatch-specific part of the transaction, as we
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305 // would do for an outermost commit.
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306 // We're already serial, so we don't need to ensure privatization safety
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307 // for other transactions here.
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308 gtm_word priv_time = 0;
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309 bool ok = disp->trycommit (priv_time);
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310 // Given that we're already serial, the trycommit better work.
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311 assert (ok);
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312 }
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313 else if (serial_lock.write_upgrade (this))
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314 {
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315 this->state |= STATE_SERIAL;
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316 // Try to commit the dispatch-specific part of the transaction, as we
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317 // would do for an outermost commit.
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318 // We have successfully upgraded to serial mode, so we don't need to
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319 // ensure privatization safety for other transactions here.
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320 // However, we are still a reader (wrt. privatization safety) until we
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321 // have either committed or restarted, so finish the upgrade after that.
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322 gtm_word priv_time = 0;
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323 if (!disp->trycommit (priv_time))
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324 restart (RESTART_SERIAL_IRR, true);
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325 gtm_thread::serial_lock.write_upgrade_finish(this);
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326 }
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327 else
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328 restart (RESTART_SERIAL_IRR, false);
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329
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330 this->state |= (STATE_SERIAL | STATE_IRREVOCABLE);
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331 set_abi_disp (dispatch_serialirr ());
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332 }
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333
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334 void ITM_REGPARM
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335 _ITM_changeTransactionMode (_ITM_transactionState state)
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336 {
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337 assert (state == modeSerialIrrevocable);
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338 gtm_thr()->serialirr_mode ();
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339 }
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