The following test failed in the JDK15 CI:

java/util/Scanner/ScanTest.java

Here's a snippet from the log file:

#section:main
----------messages:(5/210)----------
command: main ScanTest
reason: User specified action: run main/othervm ScanTest
Mode: othervm [/othervm specified]
Additional options from @modules: --add-modules jdk.localedata
elapsed time (seconds): 14.183
----------configuration:(3/42)----------
Boot Layer
  add modules: jdk.localedata

----------System.out:(18/1298)----------
#
# A fatal error has been detected by the Java Runtime Environment:
#
# SIGSEGV (0xb) at pc=0x00007f7908dc2e00, pid=18724, tid=18759
#
# JRE version: Java(TM) SE Runtime Environment (15.0+26) (build 15-ea+26-1246)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (15-ea+26-1246, mixed mode, sharing, tiered, compressed oops, g1 gc, linux-amd64)
# Problematic frame:
# v ~StubRoutines::jshort_disjoint_arraycopy
#
# Core dump will be written. Default location: Core dumps may be processed with "/opt/core.sh %p" (or dumping to /opt/mach5/mesos/work_dir/slaves/805146e6-8fdb-4552-bf9e-385b73cf7129-S349/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/d97c3f1c-4bae-49b8-a896-9d334254fa60/runs/def1be30-6b78-4a97-b992-af1e8ee83d63/testoutput/test-support/jtreg_open_test_jdk_tier1_part2/scratch/3/core.18724)
#
# An error report file with more information is saved as:
# /opt/mach5/mesos/work_dir/slaves/805146e6-8fdb-4552-bf9e-385b73cf7129-S349/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/d97c3f1c-4bae-49b8-a896-9d334254fa60/runs/def1be30-6b78-4a97-b992-af1e8ee83d63/testoutput/test-support/jtreg_open_test_jdk_tier1_part2/scratch/3/hs_err_pid18724.log
#
# If you would like to submit a bug report, please visit:
# https://bugreport.java.com/bugreport/crash.jsp
#
----------System.err:(30/1170)----------
Skip patterns : Passed
Find patterns : Passed
Find to horizon test : Passed
findInEmptyLine test : Passed
Remove test : Passed
From file : Passed
IOException test : Passed
Match patterns : Passed
Delimiter test : Passed
delim at boundary test : Passed
Use locale test : Passed
Close test : Passed
Cache test : Passed
Cache test2 : Passed
Scanning non ASCII digits : Passed
Reset test : Passed
Streams Close test : Passed
Streams Comod test : Passed
Radix out of range test : Passed
Has next test : Passed
Next test : Passed
Has Next Pattern test : Passed
Next pattern test : Passed
Scan booleans : Passed
Scan bytes : Passed
Scan shorts : Passed
Scan ints : Passed
Scan longs : Passed
Scan floats : Passed
Scan doubles : Passed
----------rerun:(36/4605)*----------

This test is failing in all Tier1 machine configs so I'm starting
this bug out as a P1.