The following test failed due to timeout in the JDK15 CI:

serviceability/sa/TestJhsdbJstackMixed.java

Here's a snippet from the log file:

#section:main
----------messages:(6/222)----------
command: main TestJhsdbJstackMixed
reason: User specified action: run main/othervm TestJhsdbJstackMixed
Mode: othervm [/othervm specified]
Timeout information:
--- Timeout information end.
elapsed time (seconds): 542.313
----------configuration:(0/0)----------
----------System.out:(2823/83351)----------
For random generator using seed: 6987791652654824436
To re-run test with same seed value please add "-Djdk.test.lib.random.seed=6987791652654824436" to command line.
Command line: ['/opt/mach5/mesos/work_dir/jib-master/install/jdk-15+31-1493/linux-x64-debug.jdk/jdk-15/fastdebug/bin/java' '-XX:MaxRAMPercentage=6' '-XX:+CreateCoredumpOnCrash' '-XX:+UseParallelGC' '-XX:+UseNUMA' '-Djava.library.path=/opt/mach5/mesos/work_dir/jib-master/install/jdk-15+31-1493/linux-x64-debug.test/hotspot/jtreg/native' '-cp' '/opt/mach5/mesos/work_dir/slaves/52628e90-e5e7-4ef3-af97-10d8776d10db-S997/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/a09de496-f095-49a3-aeb2-7e67191ae33a/runs/01764858-c14e-4d09-aff2-a2de5f71b4c0/testoutput/test-support/jtreg_open_test_hotspot_jtreg_hotspot_serviceability/classes/1/serviceability/sa/TestJhsdbJstackMixed.d:/opt/mach5/mesos/work_dir/slaves/52628e90-e5e7-4ef3-af97-10d8776d10db-S997/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/a09de496-f095-49a3-aeb2-7e67191ae33a/runs/01764858-c14e-4d09-aff2-a2de5f71b4c0/testoutput/test-support/jtreg_open_test_hotspot_jtreg_hotspot_serviceability/classes/1/test/lib' 'LingeredAppWithNativeMethod' '2809b1dd-5940-454a-8e88-08a0963d1a5d.lck']
Started LingeredApp with pid 21901
[2020-07-07T04:05:27.596129414Z] Gathering output for process 21948
Timeout refired 480 times
Attaching to process ID 21901, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 15-ea+31-1493
Deadlock Detection:

No deadlocks found.

----------------- 21943 -----------------
"NoFramePointerJNIFib" #13 prio=5 tid=0x00007fb9482a9d00 nid=0x55b7 runnable [0x00007fb90f7f0000]
   java.lang.Thread.State: RUNNABLE
   JavaThread state: _thread_in_native
0x00007fb94c03b6b0 fib + 0x30
----------------- 21935 -----------------
"Common-Cleaner" #12 daemon prio=8 tid=0x00007fb94821b910 nid=0x55af in Object.wait() [0x00007fb90fbf9000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
   JavaThread state: _thread_blocked
0x00007fb951730de2 __pthread_cond_timedwait + 0x132
----------------- 21934 -----------------
0x00007fb9508241ae MutableSpaceUsedHelper::take_sample() + 0xe
0x00007fb9506e12df PerfLongVariant::sample() + 0x1f
0x00007fb9482182d0 ????????
0x00007fb9482182d0 ????????

<snip>

0x00007fb9482182d0 ????????
0x00007fb9482182d0 ????????
0x00007fb9482182d0 ????????

DEBUG: [0x00007fb94c03b6b0 fib + 0x30]
DEBUG: Test triggered interesting condition.
DEBUG: Test PASSED.
Test Completed
 LingeredApp stdout: [For random generator using seed: -1655933452054152999
To re-run test with same seed value please add "-Djdk.test.lib.random.seed=-1655933452054152999" to command line.
fib(40) = 102334155
fib(46) = 1836311903
fib(46) = ];
 LingeredApp stderr: []
 LingeredApp exitValue = 0
----------System.err:(2/16)----------

STATUS:Passed.
----------rerun:(35/6088)*----------

Please note that the test did pass while the JTREG timeout
handler was running. It could be that the test just needs a
slightly longer default timeout value. The default timeout is
120 seconds/2 minutes and the timeoutFactor is 4 for a
total timeout value of 480 seconds/8 minutes. This test
executed in

elapsed time (seconds): 542.313