From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail5.windriver.com ([192.103.53.11]:57932 "EHLO mail5.wrs.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727256AbeLPVom (ORCPT ); Sun, 16 Dec 2018 16:44:42 -0500 Date: Sun, 16 Dec 2018 16:42:02 -0500 From: Paul Gortmaker Subject: Re: [Regression 4.15] Can't kill CONFIG_UNWINDER_ORC with fire or plague. Message-ID: <20181216214202.GQ11670@windriver.com> References: <20171226043003.GB10431@windriver.com> <20171229021323.GF10431@windriver.com> <20171229164739.rgcqmam6wtno6hge@treble> <20171229181830.GH10431@windriver.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20171229181830.GH10431@windriver.com> Sender: linux-kbuild-owner@vger.kernel.org List-ID: To: Josh Poimboeuf Cc: Randy Dunlap , Ingo Molnar , Masahiro Yamada , Michal Marek , linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org [Re: [Regression 4.15] Can't kill CONFIG_UNWINDER_ORC with fire or plague.] On 29/12/2017 (Fri 13:18) Paul Gortmaker wrote: > [Re: [Regression 4.15] Can't kill CONFIG_UNWINDER_ORC with fire or plague.] On 29/12/2017 (Fri 10:47) Josh Poimboeuf wrote: > > > This seems to be related to a kconfig quirk where only silentoldconfig > > updates the include/config/auto.conf file. The other config targets > > (oldconfig, defconfig, etc) don't touch it. It seems intentional, but I > > have no idea why. > > > > That causes the Makefile to get stale data for 'CONFIG_*' variables when > > it includes auto.conf. So I don't think this is specific to the ORC > > check. It seems like it could also cause bugs elsewhere. > > OK, good - you agree with my initial diagnosis of stale auto.conf then. > Not sure what Randy was testing when he said he couldn't reproduce it. > > > The below (ugly) patch fixes it, though I'm not sure this is the best > > way to do it. We probably need Masahiro or Michal to chime in here. > > Yep, that is why I intentionally put the kbuild folks on the To/Cc of > the original report (and ran away screaming at the prospect of debugging > Makefiles on xmas day). But with holidays and all, it might not be > until early January before they have a chance to reply. It is nearly a year later and we still have this false positive. paul@sm:~/git/linux-head$ make -j12 > /dev/null Makefile:966: *** "Cannot generate ORC metadata for CONFIG_UNWINDER_ORC=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel". Stop. paul@sm:~/git/linux-head$ grep UNWINDER_ORC .config # CONFIG_UNWINDER_ORC is not set We do know a bit more now -- the auto.conf issue has been independently confirmed and "fixed" for other subsystems/issues since, like RETPOLINE: --------------------- commit 25896d073d8a0403b07e6dec56f58e6c33678207 Author: Masahiro Yamada Date: Wed Dec 5 15:27:19 2018 +0900 x86/build: Fix compiler support check for CONFIG_RETPOLINE It is troublesome to add a diagnostic like this to the Makefile parse stage because the top-level Makefile could be parsed with a stale include/config/auto.conf. Once you are hit by the error about non-retpoline compiler, the compilation still breaks even after disabling CONFIG_RETPOLINE. --------------------- I'm not sure if we want to treat this on a per config option each time again and again, or undertake a more global kbuild approach, but it does warrant a mention and a re-examination before we "solve" this again. Paul. --