From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:54162 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932259AbcK3SvF (ORCPT ); Wed, 30 Nov 2016 13:51:05 -0500 Message-ID: <583F1F6A.5010307@redhat.com> Date: Wed, 30 Nov 2016 13:50:18 -0500 From: Prarit Bhargava MIME-Version: 1.0 Subject: Re: Odd build breakage in 4.9-rc7 References: <20161130172435.GG8563@redhat.com> <583F1A5A.7040708@redhat.com> In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kbuild-owner@vger.kernel.org List-ID: To: Linus Torvalds Cc: Jarod Wilson , Linux Kernel Mailing List , Tony Luck , zarniwhoop73@googlemail.com, Linux Kbuild mailing list On 11/30/2016 01:36 PM, Linus Torvalds wrote: > On Wed, Nov 30, 2016 at 10:28 AM, Prarit Bhargava wrote: > ]> >> In my case I tracked this to commit 3637efb00864 ("x86/mce: Add PCI quirks to >> identify Xeons with machine check recovery") which adds the include for >> generated/autoksyms.h. > > Ok, that at least makes some sense. The other blamed commit did not > seem to possibly make a difference. > >> Searching LKML and I came across a report from Ken Moffat from a month ago: >> >> http://marc.info/?l=linux-kernel&m=147794681124332&w=2 > > Does a "make clean" get rid of it forever? Or does it come back? It comes back. The steps to reproduce this are: 1. checkout latest linux.git 2. make -j112 (IOW, it occurs 100% of the time for me on a clean tree.) To work around the bug I have to do 1. checkout latest linux.git 2. comment out the include for generated/autoksyms.h at include/linux/export.h:81 3. compile with -j112 This fails loudly, but then I do 4. uncomment the include for generated/autoksyms.h at include/linux/export.h:81 5. make -j112 and this completes with a bootable kernel AFAICT. > > If it's a one-time dependency issue that is because some header > dependency addition that the automatic dependency generator hadn't > caught, that might explain a bisection failure too: once the file > happens to get rebuilt (and the dependencies re-done), it starts > working even though the "happens to be rebuilt" had nothing to do with > the original bug. Hopefully the linux-kbuild folks might be able to point us in the right direction for a fix. P.