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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 4C134C43331 for ; Sat, 28 Mar 2020 19:18:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 29E1F206E6 for ; Sat, 28 Mar 2020 19:18:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727121AbgC1TSN (ORCPT ); Sat, 28 Mar 2020 15:18:13 -0400 Received: from hua.moonlit-rail.com ([45.79.167.250]:58686 "EHLO hua.moonlit-rail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725807AbgC1TSN (ORCPT ); Sat, 28 Mar 2020 15:18:13 -0400 Received: from 209-6-248-230.s2276.c3-0.wrx-ubr1.sbo-wrx.ma.cable.rcncustomer.com ([209.6.248.230] helo=boston.moonlit-rail.com) by hua.moonlit-rail.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1jIGyC-00009R-MA for linux-kernel@vger.kernel.org; Sat, 28 Mar 2020 15:18:12 -0400 Received: from springdale.moonlit-rail.com ([192.168.71.35]) by boston.moonlit-rail.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.93) (envelope-from ) id 1jIGyC-0003ZS-7s; Sat, 28 Mar 2020 15:18:12 -0400 Subject: Re: Weird issue with epoll and kernel >= 5.0 References: To: Linux Kernel From: Kris Karas Cc: omar.kilani@gmail.com Message-ID: <72cde0de-6f4a-4928-d01b-1783ac3ee6e4@moonlit-rail.com> Date: Sat, 28 Mar 2020 15:18:12 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Omar - Omar Kilani wrote: > I've observed an issue with epoll and kernels 5.0 and above when a > system is generating a lot of epoll events. It's tough getting an audience here on LK, unless you happen to cross-post to one of the very specific mailing lists (or directly to individuals) who maintain a particular subsystem.  I just rejoined LK after a 15 year hiatus; it's a rather different neighborhood. *cough*  But I digress. My first question on your issue is, after booting, how long does it take to show up?  Can you reproduce it fairly easily?  If the answer is "Yes," and you seem to be able to afford the resources for a multi-CPU VM, then making a bisecting run would likely narrow it down to something you could then email directly to the relevant maintainer. If you are not already familiar with bisecting, the git documentation on bisecting is the definitive reference: https://git-scm.com/docs/git-bisect But it is quite long.  You can usually find a more abbreviated version by googling for " git bisect"; the ones for Arch and Ubuntu are pretty decent. Once you know which file is relevant, you can run: $ ./scripts/get_maintainer.pl --file drivers/foo/bar.c ... or whatever "git bisect" says is the culprit file, and use the script output as the To: for your email message. Good luck! Kris