Hi there, I’m still trying to piece together a reproducible test that triggers this, but I wanted to post in case someone goes “hmmm... change X might have done this”.
Basically, something’s broken (or at least, has changed enough to cause problems in user space) in epoll since 5.0. It’s still broken in 5.1-rc5. It doesn’t happen 100% of the time. It’s sort of hard to pin down but I’ve observed the following: * nginx not accepting connections under load * A java app which uses netty / NIO having strange writability semantics on channels, which confuses netty / java enough to not properly flush written data on the socket. I went and tested these Linux kernels: 4.20.17 4.19.32 4.14.111 And the issue(s) do not show up there. I’m still actively chasing this up, and will report back — I haven’t touched kernel code in 15 years so I’m a little rusty. :) Regards, Omar