ConcurrentModificationException in StyleCache.equals

[naoliv]

I was editing some data, clicked the right mouse button to scroll the image layer and got this:

ERRO: java.util.ConcurrentModificationException: java.util.ConcurrentModificationException: java.util.ConcurrentModificationException. Causa: java.util.ConcurrentModificationException: java.util.ConcurrentModificationException. Causa: java.util.ConcurrentModificationException
java.util.ConcurrentModificationException: java.util.ConcurrentModificationException: java.util.ConcurrentModificationException
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
	at java.util.concurrent.ForkJoinTask.getThrowableException(ForkJoinTask.java:593)
	at java.util.concurrent.ForkJoinTask.reportException(ForkJoinTask.java:677)
	at java.util.concurrent.ForkJoinTask.join(ForkJoinTask.java:720)
	at java.util.concurrent.ForkJoinPool.invoke(ForkJoinPool.java:2616)
	at org.openstreetmap.josm.data.osm.visitor.paint.StyledMapRenderer.render(StyledMapRenderer.java:1895)
	at org.openstreetmap.josm.gui.layer.OsmDataLayer.paint(OsmDataLayer.java:401)
	at org.openstreetmap.josm.gui.MapView.paintLayer(MapView.java:638)
	at org.openstreetmap.josm.gui.MapView.paint(MapView.java:722)
	at javax.swing.JComponent.paintChildren(JComponent.java:889)
	at javax.swing.JComponent.paint(JComponent.java:1065)
	at javax.swing.JComponent.paintChildren(JComponent.java:889)
	at javax.swing.JSplitPane.paintChildren(JSplitPane.java:1047)
	at javax.swing.JComponent.paint(JComponent.java:1065)
	at javax.swing.JComponent.paintChildren(JComponent.java:889)
	at javax.swing.JComponent.paint(JComponent.java:1065)
	at javax.swing.JComponent.paintToOffscreen(JComponent.java:5210)
	at javax.swing.BufferStrategyPaintManager.paint(BufferStrategyPaintManager.java:290)
	at javax.swing.RepaintManager.paint(RepaintManager.java:1272)
	at javax.swing.JComponent._paintImmediately(JComponent.java:5158)
	at javax.swing.JComponent.paintImmediately(JComponent.java:4969)
	at javax.swing.RepaintManager$4.run(RepaintManager.java:831)
	at javax.swing.RepaintManager$4.run(RepaintManager.java:814)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
	at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:814)
	at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:789)
	at javax.swing.RepaintManager.prePaintDirtyRegions(RepaintManager.java:738)
	at javax.swing.RepaintManager.access$1200(RepaintManager.java:64)
	at javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1732)
	at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:756)
	at java.awt.EventQueue.access$500(EventQueue.java:97)
	at java.awt.EventQueue$3.run(EventQueue.java:709)
	at java.awt.EventQueue$3.run(EventQueue.java:703)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:726)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
Caused by: java.util.ConcurrentModificationException: java.util.ConcurrentModificationException
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
	at java.util.concurrent.ForkJoinTask.getThrowableException(ForkJoinTask.java:593)
	at java.util.concurrent.ForkJoinTask.reportException(ForkJoinTask.java:677)
	at java.util.concurrent.ForkJoinTask.join(ForkJoinTask.java:720)
	at org.openstreetmap.josm.data.osm.visitor.paint.StyledMapRenderer$ComputeStyleListWorker.compute(StyledMapRenderer.java:1797)
	at org.openstreetmap.josm.data.osm.visitor.paint.StyledMapRenderer$ComputeStyleListWorker.compute(StyledMapRenderer.java:1761)
	at java.util.concurrent.RecursiveTask.exec(RecursiveTask.java:94)
	at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
	at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
	at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692)
	at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)
Caused by: java.util.ConcurrentModificationException
	at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901)
	at java.util.ArrayList$Itr.next(ArrayList.java:851)
	at java.util.AbstractList.equals(AbstractList.java:522)
	at java.util.Objects.equals(Objects.java:59)
	at org.openstreetmap.josm.gui.mappaint.DividedScale.equals(DividedScale.java:182)
	at java.util.Arrays.deepEquals0(Arrays.java:4299)
	at java.util.Arrays.deepEquals(Arrays.java:4269)
	at org.openstreetmap.josm.gui.mappaint.StyleCache.equals(StyleCache.java:73)
	at org.openstreetmap.josm.data.osm.Storage$1.equals(Storage.java:365)
	at org.openstreetmap.josm.data.osm.Storage.getBucket(Storage.java:291)
	at org.openstreetmap.josm.data.osm.Storage.putUnique(Storage.java:244)
	at org.openstreetmap.josm.gui.mappaint.StyleCache.intern(StyleCache.java:82)
	at org.openstreetmap.josm.gui.mappaint.StyleCache.put(StyleCache.java:43)
	at org.openstreetmap.josm.gui.mappaint.ElemStyles.getStyleCacheWithRange(ElemStyles.java:149)
	at org.openstreetmap.josm.gui.mappaint.ElemStyles.get(ElemStyles.java:83)
	at org.openstreetmap.josm.data.osm.visitor.paint.StyledMapRenderer$ComputeStyleListWorker.add(StyledMapRenderer.java:1838)
	at org.openstreetmap.josm.data.osm.visitor.paint.StyledMapRenderer$ComputeStyleListWorker.visit(StyledMapRenderer.java:1819)
	at org.openstreetmap.josm.data.osm.Node.accept(Node.java:214)
	at org.openstreetmap.josm.data.osm.visitor.paint.StyledMapRenderer$ComputeStyleListWorker.computeDirectly(StyledMapRenderer.java:1808)
	at org.openstreetmap.josm.data.osm.visitor.paint.StyledMapRenderer$ComputeStyleListWorker.compute(StyledMapRenderer.java:1788)
	... 6 more

I don't know exactly why this happened, nor if indeed it's related with the right button click nor I don't know how to reproduce this, sorry.

JOSM:

URL:http://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2016-02-04 01:17:15 +0100 (Thu, 04 Feb 2016)
Build-Date:2016-02-04 02:33:04
Revision:9733
Relative:URL: ^/trunk

Identification: JOSM/1.5 (9733 pt_BR) Linux Debian GNU/Linux testing (stretch)
Memory Usage: 1634 MB / 9102 MB (787 MB allocated, but free)
Java version: 1.8.0_72-internal-b05, Oracle Corporation, OpenJDK 64-Bit Server VM
VM arguments: [-Dawt.useSystemAAFontSettings=on]
Dataset consistency test: No problems found

Plugins:
- Create_grid_of_ways (31772)
- OpeningHoursEditor (31772)
- PicLayer (31895)
- RoadSigns (31895)
- SimplifyArea (31895)
- apache-commons (31895)
- buildings_tools (31895)
- conflation (0.1.9)
- contourmerge (1014)
- download_along (31772)
- editgpx (31772)
- ejml (31895)
- geotools (31895)
- imagery_offset_db (32046)
- importvec (31772)
- jts (31772)
- log4j (31895)
- measurement (31895)
- merge-overlap (31967)
- opendata (31937)
- pbf (31772)
- pdfimport (32019)
- poly (31772)
- reverter (32005)
- scripting (30722)
- todo (29154)
- turnrestrictions (31895)
- undelete (31895)
- utilsplugin2 (32018)

[bastiK]

Simon, why did you change the ExecutorService to ForkJoinPool? As far as I understand it, fork/join only makes sense if you call fork() recursively at multiple levels. But in this case, it joins only once, right?

Quote from a ​blog article:

Fork/Join, introduced in Java 7, isn't intended to replace or compete with the existing concurrency utility classes; instead it updates and completes them. Fork/Join addresses the need for divide-and-conquer, or recursive task-processing in Java programs (see Resources).

I think if ExecutorService can do the job, it should be preferred.

[simon04]

Replying to bastiK:

Simon, why did you change the ExecutorService to ForkJoinPool? As far as I understand it, fork/join only makes sense if you call fork() recursively at multiple levels. But in this case, it joins only once, right?

I tried to simplify the code, but I agree that this is not the use-case ForkJoinPool has been designed for. I'm no longer convinced whether r9351 was a good idea.

Do you think this bug is related to the ForkJoinPool usage? In r9341, org.openstreetmap.josm.gui.mappaint.StyleCache#equals has been implemented which shows up in the stacktrace.

[bastiK]

Replying to simon04:

Do you think this bug is related to the ForkJoinPool usage? In r9341, org.openstreetmap.josm.gui.mappaint.StyleCache#equals has been implemented which shows up in the stacktrace.

You are right, there is no indication that it is related to ForkJoinPool usage. But I don't think it is related to r9341 either - nothing fundamental changed in the structure and the ArrayList that causes the exception existed before.

I would expect such an exception if ElemStyles.getStyleCacheWithRange is executed for the same primitive in different threads at the same time. NavigatableComponent.isSelectablePredicate looks like a possible culprit, but it always runs in EDT, so I have no idea at the moment.

[michael2402]

Isn't this the same as #12598? Then we can close this issue.

[bastiK]

Closed as duplicate of #12598.