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=-2.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 E276CC3F2CE for ; Sat, 29 Feb 2020 03:34:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AEBF8246B4 for ; Sat, 29 Feb 2020 03:34:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="csg7gxtK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726783AbgB2DdA (ORCPT ); Fri, 28 Feb 2020 22:33:00 -0500 Received: from mail-pl1-f195.google.com ([209.85.214.195]:44846 "EHLO mail-pl1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726418AbgB2Dc7 (ORCPT ); Fri, 28 Feb 2020 22:32:59 -0500 Received: by mail-pl1-f195.google.com with SMTP id d9so1978687plo.11 for ; Fri, 28 Feb 2020 19:32:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=WWlc7PySHsdvwwIYJR3k0LGstQ/VQF9XESI8/nbyPDg=; b=csg7gxtKkqhVqKb8DlMR0ncRzgv5p7AA1oIATkymki1e+cq/FMCCQC/WaWChUx/TvQ kcOUBUiZUfMVUNtOAdCXFHv6KcUPmS6MvRJ5JMH6Ncv7NbFmPK8XhDV9GCB5tAeMNd7h Cp4ELClEzN1Xf6U10pGs9pnlWCK8TesOFZVL3VtxGQKm2vg0GBehsf7704sNmSa2SDsL bxzx+PIr17g23xdFHAciunDiNLg9p5sBAFkyoqE+rlT8EThZNShZ6quSusngWpKETcU5 pbaUYs0v/TIdje5mh4aBK0veeAyqHoQ3BHp72dAF0vGH8lq/KfT6/HcyZyWeTOmc4+eE yX/Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=WWlc7PySHsdvwwIYJR3k0LGstQ/VQF9XESI8/nbyPDg=; b=Ia795x8EbiZB8f/RLVokuuev7A2FL/bx4+ScI+qh6/ew4F9PGPYrYB1BLpW3uy/EnO OsLipaxU+NOP/WB5QqWRVl8SZPfr/0hi5sxD+JbcD28lkCoNJel4hmKk/7mXxDZE/K/f oa8bJY3qsOpi1RdJRVAA+n19QxvPBf8sjvMRLCftdn+Jhy4KrOAK+KNmHNlNtGJAR8Sj OrkWcHuYSn/ls/bVrt5a0dwwftfNxEp+RWa7YQhD0bCDEHhwn6E+yuzVj8RA/IMej6Wo fZodcCCpNVfhMoujbqwQfghICB+iVDkX4ttm3xh9NDU7doOygZxl2X1bb3246ZTe9q6v L9QQ== X-Gm-Message-State: APjAAAXYSIszIgh1omMGC4weW0IvcJNn+P5oSLjiFwyUNPoqFxmAEKuK wlefmFT+d7f0krn+PjY/v8o= X-Google-Smtp-Source: APXvYqxbEKVGTDVu4gesY42kCC0StwycrEMxDzkBFbAM++iBEiZrBE64A3hMch8AkeWudI3kvs+PDw== X-Received: by 2002:a17:90a:191a:: with SMTP id 26mr7863628pjg.111.1582947177174; Fri, 28 Feb 2020 19:32:57 -0800 (PST) Received: from localhost ([2401:fa00:8f:203:5bbb:c872:f2b1:f53b]) by smtp.gmail.com with ESMTPSA id m12sm3781362pjf.25.2020.02.28.19.32.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 28 Feb 2020 19:32:56 -0800 (PST) Date: Sat, 29 Feb 2020 12:32:53 +0900 From: Sergey Senozhatsky To: "Theodore Y. Ts'o" Cc: Petr Mladek , Greg Kroah-Hartman , Sergey Senozhatsky , Lech Perczak , Steven Rostedt , "linux-kernel@vger.kernel.org" , Arnd Bergmann , Krzysztof =?utf-8?Q?Drobi=C5=84ski?= , Pawel Lenkow , John Ogness , Tejun Heo , Peter Zijlstra Subject: Re: Regression in v4.19.106 breaking waking up of readers of /proc/kmsg and /dev/kmsg Message-ID: <20200229033253.GA212847@google.com> References: <20200227123633.GB962932@kroah.com> <42d3ce5c-5ffe-8e17-32a3-5127a6c7c7d8@camlintechnologies.com> <20200228031306.GO122464@google.com> <20200228100416.6bwathdtopwat5wy@pathway.suse.cz> <20200228105836.GA2913504@kroah.com> <20200228113214.kew4xi5tkbo7bpou@pathway.suse.cz> <20200228130217.rj6qge2en26bdp7b@pathway.suse.cz> <20200228205334.GF101220@mit.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200228205334.GF101220@mit.edu> User-Agent: Mutt/1.12.2 (2019-09-21) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (20/02/28 15:53), Theodore Y. Ts'o wrote: > > So, I would still prefer to _revert_ the commit 15341b1dd409749f > > ("char/random: silence a lockdep splat with printk()"). It calmed > > down lockdep report. The real life danger is dubious. The warning > > is printed early when the system is running on single CPU where > > it could not race. > > I'm wondering now if we should revert this commit before 5.6 comes out > (it landed in 5.6-rc1). "Is much less likely to happen given the > other random initialization patches" is not the same as "guaranteed > not to happen". > > What do folks think? Well, my 5 cents, there is nothing that prevents "too-early" printk_deferred() calls in the future. From that POV I'd probably prefer to "forbid" printk_deffered() to touch per-CPU deferred machinery until it's not "too early" anymore. Similar to what we do in printk_safe::queue_flush_work(). -ss