Deadlock with puma on JRuby 9.2.8.0

[mrnonz]

Environment

Provide at least:

• jruby 9.2.8.0 (2.5.3) 2019-08-12 a1ac7ff OpenJDK 64-Bit Server VM 25.212-b04 on 1.8.0_212-b04 +jit [linux-x86_64]
• Linux 40e871c8bb09 4.15.0-1055-azure #60-Ubuntu SMP Thu Aug 8 18:29:07 UTC 2019 x86_64 Linux

Expected Behavior

JRuby and puma (version 4.2.1) lib should receive another connection.

Actual Behavior

Puma not accept another request because it's deadlock on child process. See more detail here puma/puma#1744

---

I recommended to upgrade ruby from 2.5.3 to 2.5.7 ASAP.

thanks

[mrnonz]

I have already confirm this issue by remove puma from my project and using WEBrick (1.4.2) instead, it's worked.

[kares]

@mrnonz would it be possible for you to come up with a reproducer?

also I do not understand what you mean by:

I recommended to upgrade ruby from 2.5.3 to 2.5.7 ASAP.

[headius]

Fixed by #5917

[kares]

hey @mrnonz, still a bit confused what exactly from the stdlib 2.5.5 upgrade caused the Puma issue.
only found an issue w worker mode (MRI 2.5.5 had a Process.fork fix) which isn't supported on JRuby