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=-5.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 56D78C76191 for ; Fri, 26 Jul 2019 10:19:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2679522ADA for ; Fri, 26 Jul 2019 10:19:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564136371; bh=rnzZTI3R4YtevXWLIMuEjKk8X83MUvmSjfijAT5kr/U=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=xWlXA1eWt6d6yWqs7ABM3ldYblUgd5avSlLt80/+G0fAFLLfcOGVUFFH2rZjmJaZG SUCDYORq+kBjKpMpTrCP+kydAL+wxDbiPlqh8IzrPzyoBWM100mXroFMZFM594zP/5 Xu/DvG/UizvLLRsX5970ITfaqWEEDXG10MB0JvNk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726279AbfGZKTa (ORCPT ); Fri, 26 Jul 2019 06:19:30 -0400 Received: from mail.kernel.org ([198.145.29.99]:43746 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725815AbfGZKT3 (ORCPT ); Fri, 26 Jul 2019 06:19:29 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 89186229F9; Fri, 26 Jul 2019 10:19:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564136368; bh=rnzZTI3R4YtevXWLIMuEjKk8X83MUvmSjfijAT5kr/U=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=1we1DI8LpBv9/chtOSAbouY4rmVorOqsSHMGGPjxkJxt7btRY+Q4o55aFtMwoAAsi cRrgHskOaAglnpzfunZqY5pUd3/99JHsKEyPFGKlniwvrfet6Oe42JwlKLhCwtpi1d 76w3RRINTAdfi6dJKljuLT9YmFJLSfm1W5D9tHB4= Date: Fri, 26 Jul 2019 12:19:25 +0200 From: Greg Kroah-Hartman To: Sai Prakash Ranjan Cc: Geert Uytterhoeven , Mathieu Poirier , Suzuki K Poulose , Leo Yan , linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [Regression] Missing device nodes for ETR, ETF and STM after CONFIG_UEVENT_HELPER=n Message-ID: <20190726101925.GA22476@kroah.com> References: <20190726070429.GA15714@kroah.com> <165028a7-ff12-dd28-cc4c-57a3961dbb40@codeaurora.org> <20190726084127.GA28470@kroah.com> <097942a1-6914-2542-450f-65a6147dc7aa@codeaurora.org> <6d48f996-6297-dc69-250b-790be6d2670c@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <6d48f996-6297-dc69-250b-790be6d2670c@codeaurora.org> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 26, 2019 at 03:44:40PM +0530, Sai Prakash Ranjan wrote: > On 7/26/2019 3:14 PM, Sai Prakash Ranjan wrote: > > On 7/26/2019 2:11 PM, Greg Kroah-Hartman wrote: > > > On Fri, Jul 26, 2019 at 01:50:27PM +0530, Sai Prakash Ranjan wrote: > > > > On 7/26/2019 12:34 PM, Greg Kroah-Hartman wrote: > > > > > On Fri, Jul 26, 2019 at 11:49:19AM +0530, Sai Prakash Ranjan wrote: > > > > > > Hi, > > > > > > > > > > > > When trying to test my coresight patches, I found that etr,etf and stm > > > > > > device nodes are missing from /dev. > > > > > > > > > > I have no idea what those device nodes are. > > > > > > > > > > > Bisection gives this as the bad commit. > > > > > > > > > > > > 1be01d4a57142ded23bdb9e0c8d9369e693b26cc is the first bad commit > > > > > > commit 1be01d4a57142ded23bdb9e0c8d9369e693b26cc > > > > > > Author: Geert Uytterhoeven > > > > > > Date:   Thu Mar 14 12:13:50 2019 +0100 > > > > > > > > > > > >       driver: base: Disable CONFIG_UEVENT_HELPER by default > > > > > > > > > > > >       Since commit 7934779a69f1184f ("Driver-Core: > > > > > > disable /sbin/hotplug by > > > > > >       default"), the help text for the /sbin/hotplug fork-bomb says > > > > > >       "This should not be used today [...] creates a > > > > > > high system load, or > > > > > >       [...] out-of-memory situations during bootup".  > > > > > > The rationale for this > > > > > >       was that no recent mainstream system used this > > > > > > anymore (in 2010!). > > > > > > > > > > > >       A few years later, the complete uevent helper > > > > > > support was made optional > > > > > >       in commit 86d56134f1b67d0c ("kobject: Make support > > > > > > for uevent_helper > > > > > >       optional.").  However, if was still left enabled > > > > > > by default, to support > > > > > >       ancient userland. > > > > > > > > > > > >       Time passed by, and nothing should use this > > > > > > anymore, so it can be > > > > > >       disabled by default. > > > > > > > > > > > >       Signed-off-by: Geert Uytterhoeven > > > > > >       Signed-off-by: Greg Kroah-Hartman > > > > > > > > > > > >    drivers/base/Kconfig | 1 - > > > > > >    1 file changed, 1 deletion(-) > > > > > > > > > > > > > > > > > > Any idea on this? > > > > > > > > > > That means that who ever created those device nodes is relying on udev > > > > > to do this, and is not doing the correct thing within the kernel and > > > > > using devtmpfs. > > > > > > > > > > Any pointers to where in the kernel those devices are trying to be > > > > > created? > > > > > > > > > > > > > Somewhere in drivers/hwtracing/coresight/* probably. I am not sure, > > > > Mathieu/Suzuki would be able to point you to the exact code. > > > > > > > > Also just to add on some more details, I am using *initramfs* > > > > > > Are you using devtmpfs for your /dev/ mount? > > > > > > > I am not mounting devtmpfs. However > > > >  CONFIG_DEVTMPFS=y > >  CONFIG_DEVTMPFS_MOUNT=y > > > > Ok my initramfs is using mdev: > > */sbin/mdev -s* > > This somehow is not mounting etr, etf, stm devices when uevent-helper is > disabled. Anyways as Suzuki mentioned, using devtmpfs does fix the issue. Last I looked (many years ago) mdev requires uevent-helper in order for it to work. I recommend that if you rely on mdev to keep that option enabled, or to just use devtmpfs and udev :) thanks, greg k-h