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1 /*******************************************************************************
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2 * Copyright (c) 2003, 2006 IBM Corporation and others.
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3 * All rights reserved. This program and the accompanying materials
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4 * are made available under the terms of the Eclipse Public License v1.0
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5 * which accompanies this distribution, and is available at
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6 * http://www.eclipse.org/legal/epl-v10.html
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7 *
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8 * Contributors:
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9 * IBM - Initial API and implementation
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10 * Port to the D programming language:
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11 * Frank Benoit <benoit@tionex.de>
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12 *******************************************************************************/
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13 module dwtx.core.internal.jobs.LockManager;
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14
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15 import tango.core.Thread;
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16 import dwt.dwthelper.utils;
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17 import dwtx.dwtxhelper.Collection;
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18
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19 import dwtx.core.internal.runtime.RuntimeLog;
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20 import dwtx.core.runtime.CoreException;
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21 import dwtx.core.runtime.IStatus;
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22 import dwtx.core.runtime.MultiStatus;
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23 import dwtx.core.runtime.Status;
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24 import dwtx.core.runtime.jobs.ISchedulingRule;
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25 import dwtx.core.runtime.jobs.LockListener;
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26
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27 import dwtx.core.internal.jobs.OrderedLock;
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28 import dwtx.core.internal.jobs.DeadlockDetector;
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29 import dwtx.core.internal.jobs.Deadlock;
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30 import dwtx.core.internal.jobs.JobManager;
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31 import dwtx.core.internal.jobs.Worker;
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32
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33 /**
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34 * Stores the only reference to the graph that contains all the known
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35 * relationships between locks, rules, and the threads that own them.
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36 * Synchronizes all access to the graph on the only instance that exists in this class.
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37 *
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38 * Also stores the state of suspended locks so that they can be re-acquired with
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39 * the proper lock depth.
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40 */
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41 public class LockManager {
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42 /**
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43 * This class captures the state of suspended locks.
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44 * Locks are suspended if deadlock is detected.
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45 */
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46 private static class LockState {
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47 private int depth;
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48 private OrderedLock lock;
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49
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50 /**
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51 * Suspends ownership of the given lock, and returns the saved state.
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52 */
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53 protected static LockState suspend(OrderedLock lock) {
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54 LockState state = new LockState();
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55 state.lock = lock;
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56 state.depth = lock.forceRelease_package();
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57 return state;
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58 }
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59
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60 /**
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61 * Re-acquires a suspended lock and reverts to the correct lock depth.
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62 */
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63 public void resume() {
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64 //spin until the lock is successfully acquired
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65 //NOTE: spinning here allows the UI thread to service pending syncExecs
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66 //if the UI thread is waiting to acquire a lock.
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67 while (true) {
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68 try {
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69 if (lock.acquire(Long.MAX_VALUE))
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70 break;
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71 } catch (InterruptedException e) {
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72 //ignore and loop
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73 }
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74 }
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75 lock.setDepth_package(depth);
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76 }
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77 }
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78
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79 //the lock listener for this lock manager
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80 protected LockListener lockListener;
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81 /*
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82 * The internal data structure that stores all the relationships
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83 * between the locks (or rules) and the threads that own them.
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84 */
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85 private DeadlockDetector locks;
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86 /*
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87 * Stores thread - stack pairs where every entry in the stack is an array
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88 * of locks that were suspended while the thread was acquiring more locks
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89 * (a stack is needed because when a thread tries to re-aquire suspended locks,
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90 * it can cause deadlock, and some locks it owns can be suspended again)
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91 */
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92 private HashMap suspendedLocks;
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93
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94 public this() {
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95 // super();
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96 locks = new DeadlockDetector();
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97 suspendedLocks = new HashMap();
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98 }
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99
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100 /* (non-Javadoc)
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101 * Method declared on LockListener
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102 */
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103 public void aboutToRelease() {
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104 if (lockListener is null)
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105 return;
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106 try {
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107 lockListener.aboutToRelease();
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108 } catch (Exception e) {
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109 handleException(e);
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110 // } catch (LinkageError e) {
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111 // handleException(e);
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112 }
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113 }
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114
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115 /* (non-Javadoc)
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116 * Method declared on LockListener
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117 */
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118 public bool aboutToWait(Thread lockOwner) {
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119 if (lockListener is null)
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120 return false;
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121 try {
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122 return lockListener.aboutToWait(lockOwner);
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123 } catch (Exception e) {
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124 handleException(e);
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125 // } catch (LinkageError e) {
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126 // handleException(e);
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127 }
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128 return false;
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129 }
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130
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131 /**
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132 * This thread has just acquired a lock. Update graph.
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133 */
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134 void addLockThread(Thread thread, ISchedulingRule lock) {
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135 if (locks is null)
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136 return;
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137 try {
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138 synchronized (locks) {
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139 locks.lockAcquired(thread, lock);
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140 }
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141 } catch (Exception e) {
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142 handleInternalError(e);
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143 }
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144 }
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145
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146 /**
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147 * This thread has just been refused a lock. Update graph and check for deadlock.
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148 */
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149 void addLockWaitThread(Thread thread, ISchedulingRule lock) {
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150 if (locks is null)
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151 return;
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152 try {
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153 Deadlock found = null;
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154 synchronized (locks) {
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155 found = locks.lockWaitStart(thread, lock);
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156 }
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157 if (found is null)
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158 return;
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159 // if deadlock was detected, the found variable will contain all the information about it,
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160 // including which locks to suspend for which thread to resolve the deadlock.
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161 ISchedulingRule[] toSuspend = found.getLocks();
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162 LockState[] suspended = new LockState[toSuspend.length];
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163 for (int i = 0; i < toSuspend.length; i++)
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164 suspended[i] = LockState.suspend(cast(OrderedLock) toSuspend[i]);
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165 synchronized (suspendedLocks) {
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166 Stack prevLocks = cast(Stack) suspendedLocks.get(found.getCandidate());
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167 if (prevLocks is null)
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168 prevLocks = new Stack();
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169 prevLocks.push(new ArrayWrapperObject(suspended));
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170 suspendedLocks.put(found.getCandidate(), prevLocks);
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171 }
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172 } catch (Exception e) {
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173 handleInternalError(e);
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174 }
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175 }
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176
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177 /**
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178 * Handles exceptions that occur while calling third party code from within the
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179 * LockManager. This is essentially an in-lined version of Platform.run(ISafeRunnable)
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180 */
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181 private static void handleException(Exception e) {
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182 IStatus status;
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183 if (cast(CoreException)e ) {
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184 //logged message should not be translated
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185 status = new MultiStatus(JobManager.PI_JOBS, JobManager.PLUGIN_ERROR, "LockManager.handleException", e); //$NON-NLS-1$
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186 (cast(MultiStatus) status).merge((cast(CoreException) e).getStatus());
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187 } else {
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188 status = new Status(IStatus.ERROR, JobManager.PI_JOBS, JobManager.PLUGIN_ERROR, "LockManager.handleException", e); //$NON-NLS-1$
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189 }
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190 RuntimeLog.log(status);
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191 }
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192
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193 /**
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194 * There was an internal error in the deadlock detection code. Shut the entire
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195 * thing down to prevent further errors. Recovery is too complex as it
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196 * requires freezing all threads and inferring the present lock state.
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197 */
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198 private void handleInternalError(Exception t) {
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199 try {
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200 handleException(t);
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201 handleException(new Exception(locks.toDebugString()));
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202 } catch (Exception e2) {
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203 //ignore failure to log or to create the debug string
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204 }
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205 //discard the deadlock detector for good
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206 locks = null;
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207 }
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208
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209 /**
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210 * Returns true IFF the underlying graph is empty.
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211 * For debugging purposes only.
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212 */
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213 public bool isEmpty() {
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214 return locks.isEmpty();
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215 }
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216
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217 /**
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218 * Returns true IFF this thread either owns, or is waiting for, any locks or rules.
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219 */
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220 public bool isLockOwner() {
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221 //all job threads have to be treated as lock owners because UI thread
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222 //may try to join a job
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223 Thread current = Thread.getThis();
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224 if (cast(Worker)current )
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225 return true;
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226 if (locks is null)
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227 return false;
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228 synchronized (locks) {
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229 return locks.contains(Thread.getThis());
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230 }
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231 }
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232
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233 /**
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234 * Creates and returns a new lock.
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235 */
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236 public synchronized OrderedLock newLock() {
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237 return new OrderedLock(this);
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238 }
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239
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240 /**
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241 * Releases all the acquires that were called on the given rule. Needs to be called only once.
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242 */
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243 void removeLockCompletely(Thread thread, ISchedulingRule rule) {
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244 if (locks is null)
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245 return;
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246 try {
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247 synchronized (locks) {
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248 locks.lockReleasedCompletely(thread, rule);
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249 }
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250 } catch (Exception e) {
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251 handleInternalError(e);
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252 }
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253 }
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254
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255 /**
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256 * This thread has just released a lock. Update graph.
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257 */
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258 void removeLockThread(Thread thread, ISchedulingRule lock) {
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259 try {
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260 synchronized (locks) {
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261 locks.lockReleased(thread, lock);
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262 }
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263 } catch (Exception e) {
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264 handleInternalError(e);
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265 }
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266 }
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267
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268 /**
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269 * This thread has just stopped waiting for a lock. Update graph.
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270 */
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271 void removeLockWaitThread(Thread thread, ISchedulingRule lock) {
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272 try {
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273 synchronized (locks) {
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274 locks.lockWaitStop(thread, lock);
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275 }
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276 } catch (Exception e) {
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277 handleInternalError(e);
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278 }
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279 }
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280
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281 /**
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282 * Resumes all the locks that were suspended while this thread was waiting to acquire another lock.
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283 */
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284 void resumeSuspendedLocks(Thread owner) {
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285 LockState[] toResume;
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286 synchronized (suspendedLocks) {
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287 Stack prevLocks = cast(Stack) suspendedLocks.get(owner);
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288 if (prevLocks is null)
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289 return;
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290 toResume = arrayFromObject!(LockState)( prevLocks.pop() );
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291 if (prevLocks.empty())
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292 suspendedLocks.remove(owner);
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293 }
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294 for (int i = 0; i < toResume.length; i++)
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295 toResume[i].resume();
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296 }
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297
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298 public void setLockListener(LockListener listener) {
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299 this.lockListener = listener;
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300 }
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301 }
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