Deadlock on undo

[iloveeclipse]

After updating to I20220414-0120 we see crashes in our automated tests.
The crash is caused by an extra workspace rule taken on beginning of the undo operation, see https://github.com/eclipse-platform/eclipse.platform.ui/pull/6/files#r852668795
The undo task in question itself wants to begin the rule and waits now forever:

OperationHistoryActionHandler locked the workspace bbefore starting undo:

"main" #1 prio=6 os_prio=0 cpu=1336038.52ms elapsed=8612.16s tid=0x00007ffff001a800 nid=0x6ca9 runnable  [0x00007ffff5420000]
   java.lang.Thread.State: RUNNABLE
	at org.eclipse.swt.internal.gtk.OS.Call(Native Method)
	at org.eclipse.swt.widgets.Display.sleep(Display.java:5655)
	at org.eclipse.jface.operation.ModalContext$ModalContextThread.block(ModalContext.java:167)
	at org.eclipse.jface.operation.ModalContext.run(ModalContext.java:368)
	at org.eclipse.jface.dialogs.ProgressMonitorDialog.run(ProgressMonitorDialog.java:470)
	at org.eclipse.ui.internal.progress.ProgressMonitorJobsDialog.run(ProgressMonitorJobsDialog.java:230)
	at org.eclipse.ui.internal.progress.ProgressManager.run(ProgressManager.java:984)
	at com.advantest.itee.testflow.core.edit.engine.WriteUtil.executeWriteBack(WriteUtil.java:456)
	at com.advantest.itee.testflow.core.edit.UndoRedoOperation.undo(UndoRedoOperation.java:97)
	at org.eclipse.core.commands.operations.DefaultOperationHistory.doUndo(DefaultOperationHistory.java:407)
	at org.eclipse.core.commands.operations.DefaultOperationHistory.undo(DefaultOperationHistory.java:1149)
	at org.eclipse.ui.operations.UndoActionHandler.runCommand(UndoActionHandler.java:86)
	at org.eclipse.ui.operations.OperationHistoryActionHandler.lambda$0(OperationHistoryActionHandler.java:293)
	at org.eclipse.ui.operations.OperationHistoryActionHandler$$Lambda$3012/0x0000000842334440.run(Unknown Source)
	at org.eclipse.jface.operation.ModalContext.runInCurrentThread(ModalContext.java:434)
	at org.eclipse.jface.operation.ModalContext.run(ModalContext.java:352)
	at org.eclipse.jface.dialogs.ProgressMonitorDialog.run(ProgressMonitorDialog.java:470)
	at org.eclipse.ui.internal.operations.TimeTriggeredProgressMonitorDialog.access$1(TimeTriggeredProgressMonitorDialog.java:1)
	at org.eclipse.ui.internal.operations.TimeTriggeredProgressMonitorDialog.lambda$0(TimeTriggeredProgressMonitorDialog.java:155)
	at org.eclipse.ui.internal.operations.TimeTriggeredProgressMonitorDialog$$Lambda$3014/0x0000000842333040.run(Unknown Source)
	at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:74)
	at org.eclipse.ui.internal.operations.TimeTriggeredProgressMonitorDialog.run(TimeTriggeredProgressMonitorDialog.java:167)
	at org.eclipse.ui.operations.OperationHistoryActionHandler.run(OperationHistoryActionHandler.java:322)

Undo code tries to lock the workspace:

"ModalContext" #38513 prio=6 os_prio=0 cpu=0.22ms elapsed=951.45s tid=0x00007ffef9426800 nid=0xb5ab in Object.wait()  [0x00007fff28e70000]
   java.lang.Thread.State: WAITING (on object monitor)
	at java.lang.Object.wait(java.base@11.0.10/Native Method)
	- waiting on <no object reference available>
	at java.lang.Object.wait(java.base@11.0.10/Object.java:328)
	at org.eclipse.core.internal.jobs.ThreadJob.waitForRun(ThreadJob.java:322)
	- waiting to re-lock in wait() <0x000000104a48b9b0> (a java.lang.Object)
	at org.eclipse.core.internal.jobs.ThreadJob.joinRun(ThreadJob.java:208)
	at org.eclipse.core.internal.jobs.ImplicitJobs.begin(ImplicitJobs.java:95)
	at org.eclipse.core.internal.jobs.JobManager.beginRule(JobManager.java:311)
	at com.advantest.itee.testflow.core.edit.engine.WriteUtil.executeWriteOperation(WriteUtil.java:403)
	at com.advantest.itee.testflow.core.edit.engine.WriteUtil$2.run(WriteUtil.java:459)
	at org.eclipse.jface.operation.ModalContext$ModalContextThread.run(ModalContext.java:122)

[mickaelistria]

This is now resolved.