From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752861AbcFJXDO (ORCPT ); Fri, 10 Jun 2016 19:03:14 -0400 Received: from mout.kundenserver.de ([212.227.126.135]:55369 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752228AbcFJXDM (ORCPT ); Fri, 10 Jun 2016 19:03:12 -0400 From: Arnd Bergmann To: Linus Torvalds Cc: Sage Weil , Linux Kernel Mailing List , ceph-devel , Ilya Dryomov Subject: Re: [GIT PULL] Ceph updates for 4.7-rc1 Date: Sat, 11 Jun 2016 01:04:21 +0200 Message-ID: <3311445.Ou5N5TeFZc@wuerfel> User-Agent: KMail/5.1.3 (Linux/4.4.0-22-generic; KDE/5.18.0; x86_64; ; ) In-Reply-To: References: <3724610.gtEplKGO6B@wuerfel> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V03:K0:JLd85hG1W3Syo4h92pf3PNTNbcaBvyEdX1YXVPamIIqGANe7Ek+ MjE8lwVC076zqjY3uRSgvDbY8yw5vfQPz/c07ncBzqsCEi2Hd4qCZKkP/Q9F9T/Mu/uxFiC wWLCelpaVFVegfObBFUysthMs9zG5CbBqjAa8DKrl9G2E+t4T5IbUEj3tKJ1Ffl2WGYgH0J 9uu/OYoYIJsrXt00r1xkQ== X-UI-Out-Filterresults: notjunk:1;V01:K0:odSn7a6h2xY=:9PTflq8M6AlHVenCrsp0I9 TpFzNRD1ZgucU6Z7BXDrojDCWf/yT+nyHEst1oFtd0Gun+wMIuVf0t00RaJfqBbzwDSA6yiBK pG4vDKZbJoZcQbfgQ5REV7cFep7LEI7akLwWKKTqwPjh2EzMOZ2Ajs4LyfkiucqyCQsiUNg28 3PQ84VXDYecVKzIZvd47BmM74TJpnWVRj2yTCF+V5trZ1cQ4QbYzu5topK39jpoqGxKLCl2cZ b4EqShvNRi4F7mLF5399xwCMBz+4fxGP+5RCE5kYJ6deA0k1HZbml5W+ImPvnPBxglxzyiuCO gpD4/QMjEr8R5IWKqJafqs5nAJHwMOyuqtOiE0sf5Mg6kGmFt3ibyYAuJKtN6Fk2mtJKP4Y0y NvT0mE1wV9uzd4rpi1QzFpv/ksQc+nh9QuPj4mZkrojOnE6lQQfoutdEdqj29W2RP7XNLlKoX jjtezeX2pKcYaks544vjtz9RpAmtM65pcJaqnFlUPSax0hEgy20lY+2uOY3GSAZik5mwXkjna zUl+Q7echUlSY43RK1FWqq36DZ4uGM12S8zpQgxfUw9BMLs3W4c8Vv4/S7DcpQ1gOpaMsG8T3 2hZaZaZrPz4tYmEPBUf6XDwzNxJA7SmbqEDTagzHjtyirXE9y402H9pEylYoMorATuvNPjfWs ygcrz8VKCTkqAJktZ5jOxSb9HHtawiHike36AyrSyD8HUEsj6c4yExjzFs1J8Zdc3DPUBLh6r xwyBdNM1FuxCURRe Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Friday, June 10, 2016 2:32:21 PM CEST Linus Torvalds wrote: > On Fri, Jun 10, 2016 at 1:42 PM, Arnd Bergmann wrote: > > > > What I see is that this one exported symbol has a __crc of a different > > type from all the others: > > > > $ nm net/ceph/mon_client.o | grep __crc > > 48c2e16e A __crc_ceph_monc_get_version > > 2360d633 A __crc_ceph_monc_get_version_async > > 0c50a10a A __crc_ceph_monc_got_map > > w __crc_ceph_monc_do_statfs > > A lower-case 'w' in a symbol list just means that it's a local weak > symbol (with a upper-case 'A' meaning it's an absolute global). > > Afaik, that simply means that it never got resolved, and genksyms > never generated that absolute value for it. > > As to _why_ that happens, that's more than I can guess. We've had > problems with genksyms before, and it tends to be hard to debug. > > Is it 100% reliable for you? Because the most common problem has been > issues with subtle build races, where just causing a re-build will fix > it. In a few thousand randconfig builds, this is the only symbol I ever see the problem with, and I always see it with the same configurations after rebuilding dozens of times, including with different compiler versions (I only tried arm-gcc-4.9, arm-gcc-6.1 and x86-gcc-5.3, but that seems to cover a wide range). > Your config doesn't work for me, when I do > > cp ~/genksyms-config.txt .config > make ARCH=i386 oldconfig > > I get something else than what you had. I tried with both current -git > and the commit you pinpointed, so I don't know how you generated that > config file.. I had not tried building the entire kernel on x86, and indeed I don't see the warning there either, but I do see this one weak symbol in my configuration: arm-soc/obj-x86$ nm vmlinux | grep __crc | grep -w 'w' w __crc_ceph_monc_do_statfs Also, the .config I first uploaded was based on my randconfig tree that has some other changes to avoid all existing warnings. I've done a 'make oldconfig' on your current HEAD now and put that on http://pastebin.com/raw/EJBaG0FV just to make sure we have an identical configuration. The respective ARM .config file does produce the warning on mainline, and I've uploaded that to http://pastebin.com/3NRSFSdr I generated the x86 configuration by starting with this one and running 'make olddefconfig ARCH=x86' on it. I have found 15 more random configurations with the same symptom now, and about 50 configurations with CONFIG_CEPH_FS=m that don't show it, so I can mine the configurations for more hints next week to see what influences it. Arnd