The following tests
java/awt/Modal/OnTop/OnTopDocModal1Test.java
java/awt/Modal/OnTop/OnTopDocModal2Test.java
java/awt/Modal/OnTop/OnTopDocModal3Test.java
java/awt/Modal/OnTop/OnTopDocModal4Test.java
java/awt/Modal/OnTop/OnTopModeless1Test.java
java/awt/Modal/OnTop/OnTopModeless2Test.java
java/awt/Modal/OnTop/OnTopModeless3Test.java
java/awt/Modal/OnTop/OnTopModeless4Test.java
java/awt/Modal/OnTop/OnTopModeless5Test.java

intermittently fail on Ubuntu20.04, Ubuntu22.04

like follows
-----------------------------8<=============================
#section:main
----------messages:(7/276)----------
command: main OnTopModeless4Test
reason: User specified action: run main OnTopModeless4Test
started: Sat Oct 19 04:33:04 AMT 2024
Mode: othervm
Additional options from @modules: --add-modules java.desktop
finished: Sat Oct 19 04:33:30 AMT 2024
elapsed time (seconds): 26.553
----------configuration:(3/40)----------
Boot Layer
  add modules: java.desktop

----------System.out:(0/0)----------
----------System.err:(14/866)----------
java.lang.RuntimeException: Dialog still not visible.: expected true, was false
at jdk.test.lib.Asserts.fail(Asserts.java:634)
at jdk.test.lib.Asserts.assertTrue(Asserts.java:486)
at OnTopFDFTest.doTest(OnTopFDFTest.java:188)
at OnTopModeless4Test.main(OnTopModeless4Test.java:47)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
at java.base/java.lang.reflect.Method.invoke(Method.java:580)
at com.sun.javatest.regtest.agent.MainWrapper$MainTask.run(MainWrapper.java:138)
at java.base/java.lang.Thread.run(Thread.java:1583)

JavaTest Message: Test threw exception: java.lang.RuntimeException: Dialog still not visible.: expected true, was false
JavaTest Message: shutting down test

STATUS:Failed.`main' threw exception: java.lang.RuntimeException: Dialog still not visible.: expected true, was false
-----------------------------8<=============================

The failure was observed on x86-64, aarch64.
The issue is reproducible on jdk21.0.5
It cannot be reproduced on the latests jdk24

*Regression*: YES. The issue was not observed before 21.0.5 Most probably the failures were caused by the fix for JDK-8305825. After reverting the changes https://github.com/openjdk/jdk21u/commit/7723611d5d5f8959d69d1000fa117166e3d3c5fb the tests pass successfully.

*Reproducibility*: ~40%

*Steps to reproduce*
1. create the script launching the test in a loop

cat <<EOF >runme.sh
#!/bin/bash -x

__jtreg_home=\$1
__test_jdk=\$2
__java_opts=\$3
__test=\$4
__count=\${5:-20}

i=0
while true; do

  ((i=i+1))
  echo i: \$i

  \$__jtreg_home/bin/jtreg -v -a -testjdk:\$__test_jdk -javaoptions:"\$__java_opts" \$__test || break

  if [ "\$i" -ge "\$__count" ]; then
    break
  fi
done
EOF

2. Launch the tests as follows

bash ./runme.sh ${jtreg_home} ${test_jdk_home} "" "test/jdk/java/awt/Modal/OnTop/OnTopDocModal1Test.java test/jdk/java/awt/Modal/OnTop/OnTopDocModal2Test.java test/jdk/java/awt/Modal/OnTop/OnTopDocModal3Test.java test/jdk/java/awt/Modal/OnTop/OnTopDocModal4Test.java test/jdk/java/awt/Modal/OnTop/OnTopModeless1Test.java test/jdk/java/awt/Modal/OnTop/OnTopModeless2Test.java test/jdk/java/awt/Modal/OnTop/OnTopModeless3Test.java test/jdk/java/awt/Modal/OnTop/OnTopModeless4Test.java test/jdk/java/awt/Modal/OnTop/OnTopModeless5Test.java" 20