com/sun/jdi/JdbStopThreadTest.java failed with "RuntimeException: waitForPrompt timed out after 600 seconds"

The following test failed in the JDK19 CI:

com/sun/jdi/JdbStopThreadTest.java

Here's a snippet from the log file:

----------System.out:(32/3312)*----------
Command line: [c:\\ade\\mesos\\work_dir\\jib-master\\install\\jdk-19+10-554\\windows-x64-debug.jdk\\jdk-19\\fastdebug\\bin\\java.exe -cp T:\\testoutput\\test-support\\jtreg_open_test_jdk_jdk_jdi\\classes\\4\\com\\sun\\jdi\\JdbStopThreadTest.d;C:\\ade\\mesos\\work_dir\\jib-master\\install\\jdk-19+10-554\\src.full\\open\\test\\jdk\\com\\sun\\jdi;T:\\testoutput\\test-support\\jtreg_open_test_jdk_jdk_jdi\\classes\\4\\test\\lib;C:\\ade\\mesos\\work_dir\\jib-master\\install\\jdk-19+10-554\\src.full\\open\\test\\lib;C:\\ade\\mesos\\work_dir\\jib-master\\install\\jtreg\\6.1\\1\\bundles\\jtreg-6.1+1.zip\\jtreg\\lib\\javatest.jar;C:\\ade\\mesos\\work_dir\\jib-master\\install\\jtreg\\6.1\\1\\bundles\\jtreg-6.1+1.zip\\jtreg\\lib\\jtreg.jar -Xmx768m -XX:MaxRAMPercentage=4.16667 -Djava.io.tmpdir=t:\\testoutput\\test-support\\jtreg_open_test_jdk_jdk_jdi\\tmp -ea -esa -Xcomp -XX:+CreateCoredumpOnCrash -ea -esa -XX:CompileThreshold=100 -XX:+UnlockExperimentalVMOptions -server -XX:+TieredCompilation -XX:-DoEscapeAnalysis -agentlib:jdwp=transport=dt_socket,server=y,suspend=y JdbStopThreadTestTarg ]
[debuggee]:c:\\ade\\mesos\\work_dir\\jib-master\\install\\jdk-19+10-554\\windows-x64-debug.jdk\\jdk-19\\fastdebug\\bin\\java.exe -cp T:\\testoutput\\test-support\\jtreg_open_test_jdk_jdk_jdi\\classes\\4\\com\\sun\\jdi\\JdbStopThreadTest.d;C:\\ade\\mesos\\work_dir\\jib-master\\install\\jdk-19+10-554\\src.full\\open\\test\\jdk\\com\\sun\\jdi;T:\\testoutput\\test-support\\jtreg_open_test_jdk_jdk_jdi\\classes\\4\\test\\lib;C:\\ade\\mesos\\work_dir\\jib-master\\install\\jdk-19+10-554\\src.full\\open\\test\\lib;C:\\ade\\mesos\\work_dir\\jib-master\\install\\jtreg\\6.1\\1\\bundles\\jtreg-6.1+1.zip\\jtreg\\lib\\javatest.jar;C:\\ade\\mesos\\work_dir\\jib-master\\install\\jtreg\\6.1\\1\\bundles\\jtreg-6.1+1.zip\\jtreg\\lib\\jtreg.jar -Xmx768m -XX:MaxRAMPercentage=4.16667 -Djava.io.tmpdir=t:\\testoutput\\test-support\\jtreg_open_test_jdk_jdk_jdi\\tmp -ea -esa -Xcomp -XX:+CreateCoredumpOnCrash -ea -esa -XX:CompileThreshold=100 -XX:+UnlockExperimentalVMOptions -server -XX:+TieredCompilation -XX:-DoEscapeAnalysis -agentlib:jdwp=transport=dt_socket,server=y,suspend=y JdbStopThreadTestTarg
[debuggee] Listening for transport dt_socket at address: 54008
[jdb] Set uncaught java.lang.Throwable
[jdb] Set deferred uncaught java.lang.Throwable
[jdb] Initializing jdb ...
[jdb]
[jdb] VM Started: > No frames on the current call stack
[jdb]
[jdb] main[1]
> stop thread at JdbStopThreadTestTarg:46
[jdb] Deferring breakpoint JdbStopThreadTestTarg:46.
[jdb] It will be set after the class is loaded.
[jdb] main[1]
> run
[jdb] > Set deferred breakpoint JdbStopThreadTestTarg:46
[jdb]
[jdb] Breakpoint hit: "thread=main", JdbStopThreadTestTarg.test(), line=46 bci=4
[jdb] 46 print(thread); // @1 breakpoint
[jdb] >
> thread 1
[jdb] "1" is not a valid thread id.
[jdb] >
=======================================
Exception thrown during test execution: waitForPrompt timed out after 600 seconds, looking for '[a-zA-Z0-9_-][a-zA-Z0-9_-]*\\[[1-9][0-9]*\\] [ >]*$', in 1 lines
=======================================
> quit
[debuggee] Listening for transport dt_socket at address: 54802
[debuggee] Thread[main,5,main]
[debuggee] test
[jdb] "1" is not a valid thread id.
[jdb] >
----------System.err:(15/1119)*----------
java.lang.RuntimeException: waitForPrompt timed out after 600 seconds, looking for '[a-zA-Z0-9_-][a-zA-Z0-9_-]*\\[[1-9][0-9]*\\] [ >]*$', in 1 lines
at lib.jdb.Jdb.waitForPrompt(Jdb.java:215)
at lib.jdb.Jdb.command(Jdb.java:235)
at JdbStopThreadTest.runCases(JdbStopThreadTest.java:83)
at lib.jdb.JdbTest.run(JdbTest.java:95)
at JdbStopThreadTest.main(JdbStopThreadTest.java:58)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
at java.base/java.lang.reflect.Method.invoke(Method.java:577)
at com.sun.javatest.regtest.agent.MainWrapper$MainThread.run(MainWrapper.java:127)
at java.base/java.lang.Thread.run(Thread.java:828)

JavaTest Message: Test threw exception: java.lang.RuntimeException: waitForPrompt timed out after 600 seconds, looking for '[a-zA-Z0-9_-][a-zA-Z0-9_-]*\\[[1-9][0-9]*\\] [ >]*$', in 1 lines
JavaTest Message: shutting down test

STATUS:Failed.`main' threw exception: java.lang.RuntimeException: waitForPrompt timed out after 600 seconds, looking for '[a-zA-Z0-9_-][a-zA-Z0-9_-]*\\[[1-9][0-9]*\\] [ >]*$', in 1 lines
----------rerun:(53/5652)*----------

The test failed looking for a prompt that matching a Thread name,
but the clue to the real cause is probably this:

> thread 1
[jdb] "1" is not a valid thread id.

For some reason, the thread we're trying to switch to doesn't exist.