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comparison dwtx/core/internal/jobs/LockManager.d @ 122:9d0585bcb7aa

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Add core.jobs package
author Frank Benoit <benoit@tionex.de>
date Tue, 12 Aug 2008 02:34:21 +0200
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121:c0304616ea23 122:9d0585bcb7aa
1 /*******************************************************************************
2 * Copyright (c) 2003, 2006 IBM Corporation and others.
3 * All rights reserved. This program and the accompanying materials
4 * are made available under the terms of the Eclipse Public License v1.0
5 * which accompanies this distribution, and is available at
6 * http://www.eclipse.org/legal/epl-v10.html
7 *
8 * Contributors:
9 * IBM - Initial API and implementation
10 * Port to the D programming language:
11 * Frank Benoit <benoit@tionex.de>
12 *******************************************************************************/
13 module dwtx.core.internal.jobs.LockManager;
14
15 import tango.core.Thread;
16 import dwt.dwthelper.utils;
17 import dwtx.dwtxhelper.Collection;
18
19 import dwtx.core.internal.runtime.RuntimeLog;
20 import dwtx.core.runtime.CoreException;
21 import dwtx.core.runtime.IStatus;
22 import dwtx.core.runtime.MultiStatus;
23 import dwtx.core.runtime.Status;
24 import dwtx.core.runtime.jobs.ISchedulingRule;
25 import dwtx.core.runtime.jobs.LockListener;
26
27 import dwtx.core.internal.jobs.OrderedLock;
28 import dwtx.core.internal.jobs.DeadlockDetector;
29 import dwtx.core.internal.jobs.Deadlock;
30 import dwtx.core.internal.jobs.JobManager;
31 import dwtx.core.internal.jobs.Worker;
32
33 /**
34 * Stores the only reference to the graph that contains all the known
35 * relationships between locks, rules, and the threads that own them.
36 * Synchronizes all access to the graph on the only instance that exists in this class.
37 *
38 * Also stores the state of suspended locks so that they can be re-acquired with
39 * the proper lock depth.
40 */
41 public class LockManager {
42 /**
43 * This class captures the state of suspended locks.
44 * Locks are suspended if deadlock is detected.
45 */
46 private static class LockState {
47 private int depth;
48 private OrderedLock lock;
49
50 /**
51 * Suspends ownership of the given lock, and returns the saved state.
52 */
53 protected static LockState suspend(OrderedLock lock) {
54 LockState state = new LockState();
55 state.lock = lock;
56 state.depth = lock.forceRelease_package();
57 return state;
58 }
59
60 /**
61 * Re-acquires a suspended lock and reverts to the correct lock depth.
62 */
63 public void resume() {
64 //spin until the lock is successfully acquired
65 //NOTE: spinning here allows the UI thread to service pending syncExecs
66 //if the UI thread is waiting to acquire a lock.
67 while (true) {
68 try {
69 if (lock.acquire(Long.MAX_VALUE))
70 break;
71 } catch (InterruptedException e) {
72 //ignore and loop
73 }
74 }
75 lock.setDepth_package(depth);
76 }
77 }
78
79 //the lock listener for this lock manager
80 protected LockListener lockListener;
81 /*
82 * The internal data structure that stores all the relationships
83 * between the locks (or rules) and the threads that own them.
84 */
85 private DeadlockDetector locks;
86 /*
87 * Stores thread - stack pairs where every entry in the stack is an array
88 * of locks that were suspended while the thread was acquiring more locks
89 * (a stack is needed because when a thread tries to re-aquire suspended locks,
90 * it can cause deadlock, and some locks it owns can be suspended again)
91 */
92 private HashMap suspendedLocks;
93
94 public this() {
95 // super();
96 locks = new DeadlockDetector();
97 suspendedLocks = new HashMap();
98 }
99
100 /* (non-Javadoc)
101 * Method declared on LockListener
102 */
103 public void aboutToRelease() {
104 if (lockListener is null)
105 return;
106 try {
107 lockListener.aboutToRelease();
108 } catch (Exception e) {
109 handleException(e);
110 // } catch (LinkageError e) {
111 // handleException(e);
112 }
113 }
114
115 /* (non-Javadoc)
116 * Method declared on LockListener
117 */
118 public bool aboutToWait(Thread lockOwner) {
119 if (lockListener is null)
120 return false;
121 try {
122 return lockListener.aboutToWait(lockOwner);
123 } catch (Exception e) {
124 handleException(e);
125 // } catch (LinkageError e) {
126 // handleException(e);
127 }
128 return false;
129 }
130
131 /**
132 * This thread has just acquired a lock. Update graph.
133 */
134 void addLockThread(Thread thread, ISchedulingRule lock) {
135 if (locks is null)
136 return;
137 try {
138 synchronized (locks) {
139 locks.lockAcquired(thread, lock);
140 }
141 } catch (Exception e) {
142 handleInternalError(e);
143 }
144 }
145
146 /**
147 * This thread has just been refused a lock. Update graph and check for deadlock.
148 */
149 void addLockWaitThread(Thread thread, ISchedulingRule lock) {
150 if (locks is null)
151 return;
152 try {
153 Deadlock found = null;
154 synchronized (locks) {
155 found = locks.lockWaitStart(thread, lock);
156 }
157 if (found is null)
158 return;
159 // if deadlock was detected, the found variable will contain all the information about it,
160 // including which locks to suspend for which thread to resolve the deadlock.
161 ISchedulingRule[] toSuspend = found.getLocks();
162 LockState[] suspended = new LockState[toSuspend.length];
163 for (int i = 0; i < toSuspend.length; i++)
164 suspended[i] = LockState.suspend(cast(OrderedLock) toSuspend[i]);
165 synchronized (suspendedLocks) {
166 Stack prevLocks = cast(Stack) suspendedLocks.get(found.getCandidate());
167 if (prevLocks is null)
168 prevLocks = new Stack();
169 prevLocks.push(new ArrayWrapperObject(suspended));
170 suspendedLocks.put(found.getCandidate(), prevLocks);
171 }
172 } catch (Exception e) {
173 handleInternalError(e);
174 }
175 }
176
177 /**
178 * Handles exceptions that occur while calling third party code from within the
179 * LockManager. This is essentially an in-lined version of Platform.run(ISafeRunnable)
180 */
181 private static void handleException(Exception e) {
182 IStatus status;
183 if (cast(CoreException)e ) {
184 //logged message should not be translated
185 status = new MultiStatus(JobManager.PI_JOBS, JobManager.PLUGIN_ERROR, "LockManager.handleException", e); //$NON-NLS-1$
186 (cast(MultiStatus) status).merge((cast(CoreException) e).getStatus());
187 } else {
188 status = new Status(IStatus.ERROR, JobManager.PI_JOBS, JobManager.PLUGIN_ERROR, "LockManager.handleException", e); //$NON-NLS-1$
189 }
190 RuntimeLog.log(status);
191 }
192
193 /**
194 * There was an internal error in the deadlock detection code. Shut the entire
195 * thing down to prevent further errors. Recovery is too complex as it
196 * requires freezing all threads and inferring the present lock state.
197 */
198 private void handleInternalError(Exception t) {
199 try {
200 handleException(t);
201 handleException(new Exception(locks.toDebugString()));
202 } catch (Exception e2) {
203 //ignore failure to log or to create the debug string
204 }
205 //discard the deadlock detector for good
206 locks = null;
207 }
208
209 /**
210 * Returns true IFF the underlying graph is empty.
211 * For debugging purposes only.
212 */
213 public bool isEmpty() {
214 return locks.isEmpty();
215 }
216
217 /**
218 * Returns true IFF this thread either owns, or is waiting for, any locks or rules.
219 */
220 public bool isLockOwner() {
221 //all job threads have to be treated as lock owners because UI thread
222 //may try to join a job
223 Thread current = Thread.getThis();
224 if (cast(Worker)current )
225 return true;
226 if (locks is null)
227 return false;
228 synchronized (locks) {
229 return locks.contains(Thread.getThis());
230 }
231 }
232
233 /**
234 * Creates and returns a new lock.
235 */
236 public synchronized OrderedLock newLock() {
237 return new OrderedLock(this);
238 }
239
240 /**
241 * Releases all the acquires that were called on the given rule. Needs to be called only once.
242 */
243 void removeLockCompletely(Thread thread, ISchedulingRule rule) {
244 if (locks is null)
245 return;
246 try {
247 synchronized (locks) {
248 locks.lockReleasedCompletely(thread, rule);
249 }
250 } catch (Exception e) {
251 handleInternalError(e);
252 }
253 }
254
255 /**
256 * This thread has just released a lock. Update graph.
257 */
258 void removeLockThread(Thread thread, ISchedulingRule lock) {
259 try {
260 synchronized (locks) {
261 locks.lockReleased(thread, lock);
262 }
263 } catch (Exception e) {
264 handleInternalError(e);
265 }
266 }
267
268 /**
269 * This thread has just stopped waiting for a lock. Update graph.
270 */
271 void removeLockWaitThread(Thread thread, ISchedulingRule lock) {
272 try {
273 synchronized (locks) {
274 locks.lockWaitStop(thread, lock);
275 }
276 } catch (Exception e) {
277 handleInternalError(e);
278 }
279 }
280
281 /**
282 * Resumes all the locks that were suspended while this thread was waiting to acquire another lock.
283 */
284 void resumeSuspendedLocks(Thread owner) {
285 LockState[] toResume;
286 synchronized (suspendedLocks) {
287 Stack prevLocks = cast(Stack) suspendedLocks.get(owner);
288 if (prevLocks is null)
289 return;
290 toResume = arrayFromObject!(LockState)( prevLocks.pop() );
291 if (prevLocks.empty())
292 suspendedLocks.remove(owner);
293 }
294 for (int i = 0; i < toResume.length; i++)
295 toResume[i].resume();
296 }
297
298 public void setLockListener(LockListener listener) {
299 this.lockListener = listener;
300 }
301 }