Loom crash with very simple test case

Cay Horstmann cay at horstmann.com
Sat Dec 7 07:20:19 UTC 2019

Hi, I built Loom from scratch yesterday and ran a simple test program 
with the most current API. (BTW--not a fan of this API. It was better 
with FiberScope a few weeks ago.)

On Ubuntu Linux 18.04, it dumped core. Just FYI. I am writing a blog 
post for javaadvent.com, so it would be nice if I could provide 
something that makes a million fibers and works :-) Any ideas?



public class LoomTest2
    public static int DELAY = 10_000;

    public static void main(String[] args) throws InterruptedException
       int NTASKS = 1_000_000;
       for (int i = 1; i <= NTASKS; i++) {
          String taskname = "task-" + i;
             .task(() -> run(taskname))
       Thread.sleep(10 * DELAY);

    public static void run(String n) {
       try {
       } catch (InterruptedException ex) {

# A fatal error has been detected by the Java Runtime Environment:
#  Internal Error (continuation.cpp:2803), pid=13918, tid=13938
#  guarantee(argsize == 0) failed: for now
# JRE version: OpenJDK Runtime Environment (14.0) (build 
# Java VM: OpenJDK 64-Bit Server VM (14-internal+0-adhoc.cay.loom2, 
mixed mode, tiered, compressed oops, g1 gc, linux-amd64)
# Problematic frame:
# V  [libjvm.so+0x77f4a8]  freeze_result Freeze<Config<true, true, true, 
true, false, false>, (op_mode)0>::finalize<Compiled>(frame const&, 
hframe&, int*)+0x2c8
# Core dump will be written. Default location: Core dumps may be 
processed with "/usr/share/apport/apport %p %s %c %d %P" (or dumping to 
# An error report file with more information is saved as:
# /tmp/hs_err_pid13918.log
[thread 13939 also had an error]
[thread 13946 also had an error]
# If you would like to submit a bug report, please visit:
#   https://bugreport.java.com/bugreport/crash.jsp


Cay S. Horstmann | http://horstmann.com | mailto:cay at horstmann.com

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