[swtbot-dev] Tests get stuck due to deadlocks waiting in syncExec

[Peter Hermsdorf <peter.hermsdorf@xxxxxxxxx>]

Hi everyone,

we are in the process of migrating our RCP based product from Eclipse 
Mars to 2020-12.
Which indirectly also means updating to Java 11 and GTK3( for SWTBot tests).

After migration we face the issue that at some point the test execution 
get's stuck. (but always at the same test(s))
A thread dump shows that the SWTBot Testable thread get's stuck waiting 
for the UI thread.

Excerpt: (full dump attached as .zip file)

Thread [main] (Suspended)
            OS.g_main_context_iteration(long, boolean) line: not 
available [native method]
            Display.readAndDispatch() line: 4524
            PartRenderingEngine$5.run() line: 1157
            Realm.runWithDefault(Realm, Runnable) line: 338
            PartRenderingEngine.run(MApplicationElement, 
IEclipseContext) line: 1046
            E4Workbench.createAndRunUI(MApplicationElement) line: 155
Thread [WorkbenchTestable] (Suspended)
            waiting for: RunnableLock  (id=115)
            Object.wait(long) line: not available [native method]
            RunnableLock(Object).wait() line: 328
            UISynchronizer(Synchronizer).syncExec(Runnable) line: 253
            UISynchronizer.syncExec(Runnable) line: 133
            Display.syncExec(Runnable) line: 5895
            UIThreadRunnable$4(UIThreadRunnable).run() line: 76
            UIThreadRunnable.syncExec(Display, VoidResult) line: 201
            UIThreadRunnable.syncExec(VoidResult) line: 186
            SWTBotTreeItem(AbstractSWTBot<T>).notify(int, Event, 
Widget, Runnable) line: 197
            SWTBotTreeItem(AbstractSWTBot<T>).notify(int, Event, 
Widget) line: 155
            SWTBotTreeItem.notifyTree(int, Event) line: 237
            SWTBotTreeItem.doubleClick() line: 450

I can't see what's causing the issue here. Any idea's or hints are more 
than welcome!

Environment:
* the build is running in a docker container with Xvnc TigerVNC 1.7.0 as 
Display
* Java is the latest JustJ OpenJDK build 11.0.4
* Eclipse Target Platform is 2020-12 with SWTBot version 3.0.0.202006031738
* GTK version is 3.22.11
* GTK Theme is Adwaita
* Docker image is based on 
https://git.eclipse.org/r/plugins/gitiles/sirius/org.eclipse.sirius/+/master/releng/org.eclipse.sirius.releng/docker/build/Dockerfile

Thank you.

Bye Peter

Attachment: threaddump.zip
Description: Zip archive