From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_NEOMUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 30C2BC10F11 for ; Wed, 24 Apr 2019 21:34:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EBD1820835 for ; Wed, 24 Apr 2019 21:34:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731731AbfDXVeX (ORCPT ); Wed, 24 Apr 2019 17:34:23 -0400 Received: from mx2.suse.de ([195.135.220.15]:53424 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730946AbfDXVeX (ORCPT ); Wed, 24 Apr 2019 17:34:23 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id E108AACCD; Wed, 24 Apr 2019 21:34:21 +0000 (UTC) Date: Wed, 24 Apr 2019 14:34:15 -0700 From: Davidlohr Bueso To: Eric Wong Cc: linux-kernel@vger.kernel.org, Omar Kilani Subject: Re: Strange issues with epoll since 5.0 Message-ID: <20190424213415.7muqd4tkuxsgwigz@linux-r8p5> References: <20190424193903.swlfmfuo6cqnpkwa@dcvr> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20190424193903.swlfmfuo6cqnpkwa@dcvr> User-Agent: NeoMutt/20180323 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 24 Apr 2019, Eric Wong wrote: >Omar Kilani wrote: >> 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???. > >Maybe Davidlohr knows, since he's responsible for most of the >epoll changes in 5.0. Not really, I have not been made aware of any issues until now. > >> 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. :) A bisection and/or workload that triggers the issue would be great to see what's going on. Thanks, Davidlohr