The following test timed out in the JDK16 CI:

serviceability/sa/TestJhsdbJstackLineNumbers.java

Here's a snippet from the log file:

Output and diagnostic info for process 35828 was saved into 'pid-35828-output.log'
- LingeredAppWithBusyWork.busywork(int[]) @bci=49, line=72 (Interpreted frame)
c:\\ade\\mesos\\work_dir\\jib-master\\install\\jdk-16+15-621\\windows-x64-debug.jdk\\jdk-16\\fastdebug\\bin\\jhsdb.exe jstack --pid 6468
[2020-09-08T22:25:40.123264Z] Gathering output for process 32360
Timeout refired 480 times
[2020-09-08T22:29:21.970275200Z] Waiting for completion for process 32360
[2020-09-08T22:29:21.973266900Z] Waiting for completion finished for process 32360
Output and diagnostic info for process 32360 was saved into 'pid-32360-output.log'
- LingeredAppWithBusyWork.busywork(int[]) @bci=12, line=66 (Interpreted frame)
c:\\ade\\mesos\\work_dir\\jib-master\\install\\jdk-16+15-621\\windows-x64-debug.jdk\\jdk-16\\fastdebug\\bin\\jhsdb.exe jstack --pid 6468
[2020-09-08T22:29:22.007028500Z] Gathering output for process 36748
[2020-09-08T22:29:25.361271600Z] Waiting for completion for process 36748
[2020-09-08T22:29:25.361271600Z] Waiting for completion finished for process 36748
Output and diagnostic info for process 36748 was saved into 'pid-36748-output.log'
- LingeredAppWithBusyWork.busywork(int[]) @bci=50, line=72 (Interpreted frame)
c:\\ade\\mesos\\work_dir\\jib-master\\install\\jdk-16+15-621\\windows-x64-debug.jdk\\jdk-16\\fastdebug\\bin\\jhsdb.exe jstack --pid 6468
[2020-09-08T22:29:25.370306900Z] Gathering output for process 24608
[2020-09-08T22:29:28.369446900Z] Waiting for completion for process 24608
[2020-09-08T22:29:28.369446900Z] Waiting for completion finished for process 24608
Output and diagnostic info for process 24608 was saved into 'pid-24608-output.log'
- LingeredAppWithBusyWork.busywork(int[]) @bci=9, line=65 (Interpreted frame)
Found needed line numbers after 19 iterations
Found Line Numbers: [64, 65, 66, 68, 72]
 LingeredApp stdout: [];
 LingeredApp stderr: []
 LingeredApp exitValue = 0
LingeredAppWithBusyWork finished
----------System.err:(1/16)----------
STATUS:Passed.
----------rerun:(41/5697)*----------

Please note that the "Timeout refired 480 times" output
indicates that the test timeout handler was invoked.
Please note that the "STATUS:Passed." output indicates
that the test managed to pass while the timeout handler
was running.

Here are the timestamps:

start=Tue Sep 08 22\:21\:09 GMT 2020
end=Tue Sep 08 22\:30\:11 GMT 2020
elapsed=536967 0\:08\:56.967

This failure sighting happened with fastdebug bits on Win*.
It could be that this test needs a slightly longer default timeout
value. The default timeout value is 2 minutes/120 seconds
and the default timeoutFactor is 4. So we have a total timeout
value of 8 minutes/480 seconds.