kern/56828: futex calls in Linux emulation sometimes hang

[Thomas Klausner <wiz%NetBSD.org@localhost>]

>Number:         56828
>Category:       kern
>Synopsis:       futex calls in Linux emulation sometimes hang
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri May 13 09:55:00 +0000 2022
>Originator:     Thomas Klausner
>Release:        NetBSD 9.99.96
>Organization:

>Environment:
	
	
Architecture: x86_64
Machine: amd64
>Description:
I'm using a Java application running under Linux emulation.
It sometimes hangs and ps says it's in futex:

ps -alxwww | grep java

1000 20124 19935 581925  83  0 37599660 110892 futex   Sl+  ttyp7    0:02.57 /usr/pkg/java/oracle-8/bin/java -cp /usr/pkg/PDF-Over/lib/* at.asit.pdfover.gui.Main file.pdf

Usually I can CTRL-C and restart it, and about 1/3 or 1/5 of tries
I can finish what I want to do with it.

>How-To-Repeat:
Install PDF-Over by downloading
https://webstart.buergerkarte.at/PDF-Over/setup_pdf-over_linux.jar

Install it using oracle-jre8-8.0.202:

oracle8-java -jar setup_pdf-over_linux.jar

Run it, using some variant of

/usr/pkg/bin/oracle8-java -cp "/installation/path/PDF-Over/lib/*" at.asit.pdfover.gui.Main "$@"

on a PDF file.
Sometimes it hangs before displaying the first screen, i.e. it pops up
a new window but that window stays gray. If you get further than that, just
ctrl-c and try again.

>Fix:
Yes, please!

>Unformatted: