JDK 13 EA: 100% CPU use with no Java threads runnable

Ioi Lam ioi.lam at oracle.com
Sat Sep 14 21:40:53 UTC 2019

Hi Stefan,

Is it possible for you to create a test case that reproduce this problem?

If not, try running the program inside a Linux terminal, and when the 
CPU goes at 100%, type "Ctrl-\" (Control + Backslash). It lists the 
states of all the threads that the JVM knows about. It might give you 
some idea what's happening.

An alternative is to run your program inside gdb,

$ gdb jdk13/bin/java
(gdb) handle SIGSEGV noprint
(gdb) handle SIGSEGV nostop
(gdb) set print thread-events off
(gdb) set height 0
(gdb) run -cp myapp.jar App

(When the program enters the 100% CPU state, type Ctrl-C)

Thread 1 "java" received signal SIGINT, Interrupt.
0x00007ffff779798d in pthread_join (threadid=140737353910016, 
thread_return=0x7fffffff8508) at pthread_join.c:90
90    pthread_join.c: No such file or directory.
(gdb) thread apply all where

This will list all stacks of all the threads, including ones that the 
JVM may not be aware of. This should tell you who is spinning the CPU.

- Ioi

On 9/14/19 1:57 PM, Stefan Reich wrote:
> Hi,
> I was advised by Oracle's Fairoz Matte to contact this list.
> I am seeing a Java process use 100% of one CPU core continuously, but no
> Java threads are runnable (as evidenced by internal thread sampling as well
> as VisualVM).
> Whenever it occurs, the problem does not seem to go away until the Java VM
> exits.
> I think I am using a single native library (OSHI), the rest is pure Java.
> Older versions of the JDK have exhibited the same problem, but most
> interestingly, the bug is happening right now on a Linux machine
> (Peppermint 7 I think) with OpenJDK 13 EA Build 31.
> I can perform any test on this machine that you instruct me to.
> Please advise,
> Stefan

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