The test is failing with a "crash":

#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (c:\sb\prod\1757334802\workspace\open\src\hotspot\share\runtime\safepoint.cpp:663), pid=8596, tid=12032
# fatal error: Safepoint sync time longer than 300.000000 ms detected when executing SafepointALot.

The probolem is that the test internally sets its delays using:

     "-XX:SafepointTimeoutDelay=" + Utils.adjustTimeout(300),
     "-XX:GuaranteedSafepointInterval=" + Utils.adjustTimeout(300),

which since JDK-8260555 evaluates to 300 as shown, rather than the 1200 it was previously. These values need adjusting so that there is sufficient time for the test to do what it needs.