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1 /*
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2 * Copyright 1998-2007 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 // WARNING:
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26 // This is a very sensitive and fragile class. DO NOT make any
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27 // change unless you are fully aware of the underlying semantics.
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28
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29 // This class can not inherit from any other class, because I have
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30 // to let the displaced header be the very first word. Otherwise I
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31 // have to let markOop include this file, which would export the
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32 // monitor data structure to everywhere.
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33 //
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34 // The ObjectMonitor class is used to implement JavaMonitors which have
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35 // transformed from the lightweight structure of the thread stack to a
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36 // heavy weight lock due to contention
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37
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38 // It is also used as RawMonitor by the JVMTI
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39
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40
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41 class ObjectWaiter;
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42
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43 class ObjectMonitor {
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44 public:
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45 enum {
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46 OM_OK, // no error
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47 OM_SYSTEM_ERROR, // operating system error
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48 OM_ILLEGAL_MONITOR_STATE, // IllegalMonitorStateException
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49 OM_INTERRUPTED, // Thread.interrupt()
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50 OM_TIMED_OUT // Object.wait() timed out
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51 };
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52
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53 public:
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54 // TODO-FIXME: the "offset" routines should return a type of off_t instead of int ...
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55 // ByteSize would also be an appropriate type.
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56 static int header_offset_in_bytes() { return offset_of(ObjectMonitor, _header); }
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57 static int object_offset_in_bytes() { return offset_of(ObjectMonitor, _object); }
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58 static int owner_offset_in_bytes() { return offset_of(ObjectMonitor, _owner); }
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59 static int count_offset_in_bytes() { return offset_of(ObjectMonitor, _count); }
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60 static int recursions_offset_in_bytes() { return offset_of(ObjectMonitor, _recursions); }
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61 static int cxq_offset_in_bytes() { return offset_of(ObjectMonitor, _cxq) ; }
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62 static int succ_offset_in_bytes() { return offset_of(ObjectMonitor, _succ) ; }
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63 static int EntryList_offset_in_bytes() { return offset_of(ObjectMonitor, _EntryList); }
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64 static int FreeNext_offset_in_bytes() { return offset_of(ObjectMonitor, FreeNext); }
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65 static int WaitSet_offset_in_bytes() { return offset_of(ObjectMonitor, _WaitSet) ; }
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66 static int Responsible_offset_in_bytes() { return offset_of(ObjectMonitor, _Responsible);}
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67 static int Spinner_offset_in_bytes() { return offset_of(ObjectMonitor, _Spinner); }
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68
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69 public:
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70 // Eventaully we'll make provisions for multiple callbacks, but
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71 // now one will suffice.
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72 static int (*SpinCallbackFunction)(intptr_t, int) ;
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73 static intptr_t SpinCallbackArgument ;
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74
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75
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76 public:
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77 ObjectMonitor();
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78 ~ObjectMonitor();
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79
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80 markOop header() const;
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81 void set_header(markOop hdr);
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82
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83 intptr_t is_busy() const;
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84 intptr_t is_entered(Thread* current) const;
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85
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86 void* owner() const;
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87 void set_owner(void* owner);
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88
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89 intptr_t waiters() const;
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90
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91 intptr_t count() const;
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92 void set_count(intptr_t count);
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93 intptr_t contentions() const ;
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94
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95 // JVM/DI GetMonitorInfo() needs this
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96 Thread * thread_of_waiter (ObjectWaiter *) ;
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97 ObjectWaiter * first_waiter () ;
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98 ObjectWaiter * next_waiter(ObjectWaiter* o);
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99
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100 intptr_t recursions() const { return _recursions; }
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101
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102 void* object() const;
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103 void* object_addr();
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104 void set_object(void* obj);
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105
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106 bool check(TRAPS); // true if the thread owns the monitor.
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107 void check_slow(TRAPS);
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108 void clear();
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109 #ifndef PRODUCT
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110 void verify();
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111 void print();
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112 #endif
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113
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114 bool try_enter (TRAPS) ;
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115 void enter(TRAPS);
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116 void exit(TRAPS);
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117 void wait(jlong millis, bool interruptable, TRAPS);
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118 void notify(TRAPS);
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119 void notifyAll(TRAPS);
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120
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121 // Use the following at your own risk
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122 intptr_t complete_exit(TRAPS);
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123 void reenter(intptr_t recursions, TRAPS);
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124
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125 int raw_enter(TRAPS);
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126 int raw_exit(TRAPS);
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127 int raw_wait(jlong millis, bool interruptable, TRAPS);
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128 int raw_notify(TRAPS);
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129 int raw_notifyAll(TRAPS);
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130
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131 private:
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132 // JVMTI support -- remove ASAP
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133 int SimpleEnter (Thread * Self) ;
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134 int SimpleExit (Thread * Self) ;
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135 int SimpleWait (Thread * Self, jlong millis) ;
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136 int SimpleNotify (Thread * Self, bool All) ;
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137
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138 private:
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139 void Recycle () ;
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140 void AddWaiter (ObjectWaiter * waiter) ;
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141
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142 ObjectWaiter * DequeueWaiter () ;
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143 void DequeueSpecificWaiter (ObjectWaiter * waiter) ;
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144 void EnterI (TRAPS) ;
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145 void ReenterI (Thread * Self, ObjectWaiter * SelfNode) ;
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146 void UnlinkAfterAcquire (Thread * Self, ObjectWaiter * SelfNode) ;
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147 int TryLock (Thread * Self) ;
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148 int NotRunnable (Thread * Self, Thread * Owner) ;
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149 int TrySpin_Fixed (Thread * Self) ;
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150 int TrySpin_VaryFrequency (Thread * Self) ;
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151 int TrySpin_VaryDuration (Thread * Self) ;
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152 void ctAsserts () ;
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153 void ExitEpilog (Thread * Self, ObjectWaiter * Wakee) ;
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154 bool ExitSuspendEquivalent (JavaThread * Self) ;
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155
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156 private:
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157 friend class ObjectSynchronizer;
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158 friend class ObjectWaiter;
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159 friend class VMStructs;
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160
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161 // WARNING: this must be the very first word of ObjectMonitor
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162 // This means this class can't use any virtual member functions.
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163 // TODO-FIXME: assert that offsetof(_header) is 0 or get rid of the
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164 // implicit 0 offset in emitted code.
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165
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166 volatile markOop _header; // displaced object header word - mark
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167 void* volatile _object; // backward object pointer - strong root
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168
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169 double SharingPad [1] ; // temp to reduce false sharing
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170
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171 // All the following fields must be machine word aligned
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172 // The VM assumes write ordering wrt these fields, which can be
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173 // read from other threads.
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174
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175 void * volatile _owner; // pointer to owning thread OR BasicLock
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176 volatile intptr_t _recursions; // recursion count, 0 for first entry
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177 int OwnerIsThread ; // _owner is (Thread *) vs SP/BasicLock
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178 ObjectWaiter * volatile _cxq ; // LL of recently-arrived threads blocked on entry.
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179 // The list is actually composed of WaitNodes, acting
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180 // as proxies for Threads.
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181 ObjectWaiter * volatile _EntryList ; // Threads blocked on entry or reentry.
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182 Thread * volatile _succ ; // Heir presumptive thread - used for futile wakeup throttling
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183 Thread * volatile _Responsible ;
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184 int _PromptDrain ; // rqst to drain cxq into EntryList ASAP
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185
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186 volatile int _Spinner ; // for exit->spinner handoff optimization
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187 volatile int _SpinFreq ; // Spin 1-out-of-N attempts: success rate
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188 volatile int _SpinClock ;
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189 volatile int _SpinDuration ;
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190 volatile intptr_t _SpinState ; // MCS/CLH list of spinners
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191
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192 // TODO-FIXME: _count, _waiters and _recursions should be of
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193 // type int, or int32_t but not intptr_t. There's no reason
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194 // to use 64-bit fields for these variables on a 64-bit JVM.
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195
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196 volatile intptr_t _count; // reference count to prevent reclaimation/deflation
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197 // at stop-the-world time. See deflate_idle_monitors().
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198 // _count is approximately |_WaitSet| + |_EntryList|
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199 volatile intptr_t _waiters; // number of waiting threads
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200 ObjectWaiter * volatile _WaitSet; // LL of threads wait()ing on the monitor
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201 volatile int _WaitSetLock; // protects Wait Queue - simple spinlock
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202
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203 public:
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204 int _QMix ; // Mixed prepend queue discipline
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205 ObjectMonitor * FreeNext ; // Free list linkage
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206 intptr_t StatA, StatsB ;
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207
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208 };
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