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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3F7CDC05027 for ; Mon, 23 Jan 2023 21:28:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232868AbjAWV2K (ORCPT ); Mon, 23 Jan 2023 16:28:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54776 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231802AbjAWV2J (ORCPT ); Mon, 23 Jan 2023 16:28:09 -0500 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 734629768; Mon, 23 Jan 2023 13:28:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Sender:Reply-To:Content-ID:Content-Description; bh=H3eXFipHsSf5mXLYhxHs1ARXh2uZcFDldjjmb+JSZds=; b=WxCR35uVG/MHKyfylbTGXofvgy KbP19KdHikwwEEKYXwzQ3wMqB4bG0r9Nszcz1IhUPbpC8z1BMf+Jl71dqO4u1XHpyB6tpN8U+Cev+ APcUGdIdctJujiyDtiYCIiGINpouK+AR7O1OxlIqlUtW+QI9exsyVlC0/BGodgBT8TSwtPYNmW7D3 +scgoI6ZLYMBbBD1vAwL1ZFlgcQ7cZoH+5NdNoF7E/jhOALR+S6PbW+s5PDNtNlLiK0Pgq714g21v w/nGJgxpfg5mbcoDZJhrvDEWn7DX7gDd7JpOLREDBZUEJSvbel3xmUL7wP2MSZRPWWa9UrxWtNS6+ BYF5wWNQ==; Received: from [2601:1c2:d80:3110::9307] by bombadil.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1pK4MF-001VoA-PM; Mon, 23 Jan 2023 21:28:03 +0000 Message-ID: <678ad23e-e7b6-a570-897b-81f1f3ef7224@infradead.org> Date: Mon, 23 Jan 2023 13:28:02 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.1 Subject: Re: [PATCH] printk: Document that CONFIG_BOOT_PRINTK_DELAY required for boot_delay= Content-Language: en-US To: Bjorn Helgaas , Matthew Wilcox Cc: Jonathan Corbet , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Bjorn Helgaas References: <20230123204419.GA980727@bhelgaas> From: Randy Dunlap In-Reply-To: <20230123204419.GA980727@bhelgaas> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/23/23 12:44, Bjorn Helgaas wrote: > On Mon, Jan 23, 2023 at 06:18:26PM +0000, Matthew Wilcox wrote: >> On Mon, Jan 23, 2023 at 12:04:40PM -0600, Bjorn Helgaas wrote: >>> From: Bjorn Helgaas >>> >>> Document the fact that CONFIG_BOOT_PRINTK_DELAY must be enabled for the >>> "boot_delay" kernel parameter to work. Also mention that "lpj=" may be >>> necessary. >>> >>> Signed-off-by: Bjorn Helgaas >>> --- >>> Documentation/admin-guide/kernel-parameters.txt | 5 +++-- >>> 1 file changed, 3 insertions(+), 2 deletions(-) >>> >>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt >>> index 6cfa6e3996cf..b0b40b6a765c 100644 >>> --- a/Documentation/admin-guide/kernel-parameters.txt >>> +++ b/Documentation/admin-guide/kernel-parameters.txt >>> @@ -480,8 +480,9 @@ >>> See Documentation/block/cmdline-partition.rst >>> >>> boot_delay= Milliseconds to delay each printk during boot. >>> - Values larger than 10 seconds (10000) are changed to >>> - no delay (0). >>> + Enable CONFIG_BOOT_PRINTK_DELAY and also specify >>> + "lpj=". Boot_delay values larger than 10 seconds >>> + (10000) are changed to no delay (0). >> >> That's counterintuitive. I'd understand clamping it to 10 seconds, >> but not setting it to zero. > > I'm not opposed to setting it to 10 sec instead of 0, but that came > from bfe8df3d314b ("slow down printk during boot"); added Randy in > case he wants to comment. I'm not opposed to a patch that clamps the max boot_delay to 10 seconds. I expect that my thinking in 2007 was that any larger value was just some random/garbage value so it should be ignored. >> Also, there are two ways of reading this. One is that by specifying >> boot_delay=, lpj= is set to a sane value. The other (intended?) is >> that in order to use this option, you must also specify lpj=. You probably should specify lpj= (e.g., from some previous boot log), as indicated in the BOOT_PRINTK_DELAY Kconfig help text in lib/Kconfig.debug. > Maybe this is better? > > boot_delay= Milliseconds to delay each printk during boot. > - Values larger than 10 seconds (10000) are changed to > - no delay (0). > + Only works if CONFIG_BOOT_PRINTK_DELAY is enabled, > + and you may also have to specify "lpj=". Boot_delay > + values larger than 10 seconds (10000) are changed > + to no delay (0). > Format: integer That's fine with me. -- ~Randy