To reproduce run several times
sudo jtreg -concurrency:12 -v1 langtools/test/jdk/jshell

There are several issues here. See attached jtr files.

1.
Caused by: java.lang.IllegalStateException: Launching JShell execution engine threw: Accept timed out
at jdk.jshell/jdk.jshell.JShell.<init>(JShell.java:139)
at jdk.jshell/jdk.jshell.JShell$Builder.build(JShell.java:405)
at jdk.jshell/jdk.jshell.JShell.create(JShell.java:420)
at KullaTesting.<clinit>(KullaTesting.java:103)
... 29 more
Caused by: java.net.SocketTimeoutException: Accept timed out
at java.base/java.net.PlainSocketImpl.socketAccept(Native Method)
at java.base/java.net.AbstractPlainSocketImpl.accept(AbstractPlainSocketImpl.java:459)
at java.base/java.net.ServerSocket.implAccept(ServerSocket.java:551)
at java.base/java.net.ServerSocket.accept(ServerSocket.java:519)
at jdk.jshell/jdk.jshell.execution.JdiDefaultExecutionControl.create(JdiDefaultExecutionControl.java:116)
at jdk.jshell/jdk.jshell.execution.JdiExecutionControlProvider.generate(JdiExecutionControlProvider.java:148)
at jdk.jshell/jdk.jshell.spi.ExecutionControl.generate(ExecutionControl.java:179)
at jdk.jshell/jdk.jshell.spi.ExecutionControl.generate(ExecutionControl.java:296)
at jdk.jshell/jdk.jshell.execution.FailOverExecutionControlProvider.generate(FailOverExecutionControlProvider.java:103)
at jdk.jshell/jdk.jshell.spi.ExecutionControl.generate(ExecutionControl.java:179)
at jdk.jshell/jdk.jshell.spi.ExecutionControl.generate(ExecutionControl.java:296)
at jdk.jshell/jdk.jshell.JShell.<init>(JShell.java:136)


2.
java.lang.IllegalStateException: Launching JShell execution engine threw: Failed remote listen: java.util.concurrent.ExecutionException: com.sun.jdi.connect.TransportTimeoutException: timeout waiting for connection @ com.sun.jdi.SocketListen (defaults: timeout=, port=, localAddress=) -- {timeout=timeout=5000, port=port=, localAddress=localAddress=127.0.0.1}
at jdk.jshell/jdk.jshell.JShell.<init>(JShell.java:139)
at jdk.jshell/jdk.jshell.JShell$Builder.build(JShell.java:405)
at KullaTesting.setUp(KullaTesting.java:197)
at KullaTesting.setUp(KullaTesting.java:169)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:85)
at org.testng.internal.Invoker.invokeConfigurationMethod(Invoker.java:510)
at org.testng.internal.Invoker.invokeConfigurations(Invoker.java:211)
at org.testng.internal.Invoker.invokeMethod(Invoker.java:585)
at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:821)
at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1131)
at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:124)
at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:108)
at org.testng.TestRunner.privateRun(TestRunner.java:773)
at org.testng.TestRunner.run(TestRunner.java:623)
at org.testng.SuiteRunner.runTest(SuiteRunner.java:357)
at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:352)
at org.testng.SuiteRunner.privateRun(SuiteRunner.java:310)
at org.testng.SuiteRunner.run(SuiteRunner.java:259)
at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:86)
at org.testng.TestNG.runSuitesSequentially(TestNG.java:1185)
at org.testng.TestNG.runSuitesLocally(TestNG.java:1110)
at org.testng.TestNG.run(TestNG.java:1018)
at com.sun.javatest.regtest.agent.TestNGRunner.main(TestNGRunner.java:94)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at com.sun.javatest.regtest.agent.MainActionHelper$SameVMRunnable.run(MainActionHelper.java:230)
at java.base/java.lang.Thread.run(Thread.java:844)
Caused by: java.lang.InternalError: Failed remote listen: java.util.concurrent.ExecutionException: com.sun.jdi.connect.TransportTimeoutException: timeout waiting for connection @ com.sun.jdi.SocketListen (defaults: timeout=, port=, localAddress=) -- {timeout=timeout=5000, port=port=, localAddress=localAddress=127.0.0.1}
at jdk.jshell/jdk.jshell.execution.JdiInitiator.reportLaunchFail(JdiInitiator.java:300)
at jdk.jshell/jdk.jshell.execution.JdiInitiator.listenTarget(JdiInitiator.java:199)
at jdk.jshell/jdk.jshell.execution.JdiInitiator.<init>(JdiInitiator.java:111)
at jdk.jshell/jdk.jshell.execution.JdiDefaultExecutionControl.create(JdiDefaultExecutionControl.java:103)
at jdk.jshell/jdk.jshell.execution.JdiExecutionControlProvider.generate(JdiExecutionControlProvider.java:148)
at jdk.jshell/jdk.jshell.spi.ExecutionControl.generate(ExecutionControl.java:179)
at jdk.jshell/jdk.jshell.spi.ExecutionControl.generate(ExecutionControl.java:296)
at jdk.jshell/jdk.jshell.execution.FailOverExecutionControlProvider.generate(FailOverExecutionControlProvider.java:103)
at jdk.jshell/jdk.jshell.spi.ExecutionControl.generate(ExecutionControl.java:179)
at jdk.jshell/jdk.jshell.spi.ExecutionControl.generate(ExecutionControl.java:296)
at jdk.jshell/jdk.jshell.JShell.<init>(JShell.java:136)
... 33 more
Caused by: java.util.concurrent.ExecutionException: com.sun.jdi.connect.TransportTimeoutException: timeout waiting for connection
at java.base/java.util.concurrent.FutureTask.report(FutureTask.java:122)
at java.base/java.util.concurrent.FutureTask.get(FutureTask.java:205)
at jdk.jshell/jdk.jshell.execution.JdiInitiator.timedVirtualMachineCreation(JdiInitiator.java:244)
at jdk.jshell/jdk.jshell.execution.JdiInitiator.listenTarget(JdiInitiator.java:176)
... 42 more
Caused by: com.sun.jdi.connect.TransportTimeoutException: timeout waiting for connection
at jdk.jdi/com.sun.tools.jdi.SocketTransportService.accept(SocketTransportService.java:353)
at jdk.jdi/com.sun.tools.jdi.GenericListeningConnector.accept(GenericListeningConnector.java:151)
at jdk.jshell/jdk.jshell.execution.JdiInitiator.lambda$listenTarget$1(JdiInitiator.java:176)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1161)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)