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 9A0BBC25B50 for ; Mon, 23 Jan 2023 20:44:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229956AbjAWUo0 (ORCPT ); Mon, 23 Jan 2023 15:44:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45574 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231560AbjAWUoX (ORCPT ); Mon, 23 Jan 2023 15:44:23 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D494330D8; Mon, 23 Jan 2023 12:44:22 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 44BC261029; Mon, 23 Jan 2023 20:44:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 69360C433D2; Mon, 23 Jan 2023 20:44:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1674506661; bh=nsRBbpy3niV2zB0JxDiw6NxHMjalKZwL+jxcCxjKFKI=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=qEGStwSlAwZla16k5WKaM58Gxev2Ji1uStrqOiyogyWRCZ7wdeyuiR0PsgJUDjOc2 7n5mjn4X2gNYwBBR/NLr0pDbSf6qR+y631De8LcEuiwT92WFOxdqMjKk1AcFSR+GPl U4Shw7g+wU68Il+2HkZwTqx00cBT7AC3DVgcKkWCUM45Or7+Pq9+UE2j3lIbAPr1XO 57WPhHhxbVICxcE0IJV/QizhFdN/Ctj2WO4srfoRrlgdir+ml6lHCz3DyU+2mGuOBe bDzgipsvh8k1mIKTu1SmfifbPTzqoYD1MW9IbKaRSioWrl5adaepzogdPJpHrT3nQc fNzqFV7/WHdkg== Date: Mon, 23 Jan 2023 14:44:19 -0600 From: Bjorn Helgaas To: Matthew Wilcox Cc: Jonathan Corbet , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Bjorn Helgaas , Randy Dunlap Subject: Re: [PATCH] printk: Document that CONFIG_BOOT_PRINTK_DELAY required for boot_delay= Message-ID: <20230123204419.GA980727@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org 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. > 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=. 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 bootconfig [KNL]