The following 4 tests timed out in the JDK18 CI:

applications/microbenchmarks/other/Test_15.java#id7
applications/microbenchmarks/other/Test_15.java#id6
applications/microbenchmarks/other/Test_15.java#id5
applications/microbenchmarks/other/Test_15.java#id4

Here's a log file snippet from Test_15.java#id7:

#section:driver
----------messages:(9/500)----------
command: driver applications.microbenchmarks.MicroRunner -f 1 -foe true org.openjdk.strings.charat.CharAtStreamBench.test_cmp1$
reason: User specified action: run driver/timeout=360 applications.microbenchmarks.MicroRunner -f 1 -foe true org.openjdk.strings.charat.CharAtStreamBench.test_cmp1$
Mode: agentvm
Agent id: 8
Additional opens to unnamed modules from @modules: java.base/java.io
Timeout refired 3600 times
Timeout information:
--- Timeout information end.
elapsed time (seconds): 3622.438
----------configuration:(18/2323)----------

<snip>

result: Error. Agent error: java.lang.Exception: Agent 8 timed out with a timeout of 3600 seconds; check console log for any additional details


There's no indication that this test passed while the timeout handler
was running nor is there any indication what caused the test to
timeout.

The same lack of indicators is present in the other failing sub-tests.

The test task's JVM args are:

-XX:+CreateCoredumpOnCrash -ea -esa -XX:CompileThreshold=100 -XX:+UnlockExperimentalVMOptions -server -XX:-TieredCompilation

I'm starting this bug in hotspot/test so that someone who knows
these tests can triage the failures.