From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753991AbcA0H7W (ORCPT ); Wed, 27 Jan 2016 02:59:22 -0500 Received: from e06smtp15.uk.ibm.com ([195.75.94.111]:60845 "EHLO e06smtp15.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753937AbcA0H7R (ORCPT ); Wed, 27 Jan 2016 02:59:17 -0500 X-IBM-Helo: d06dlp02.portsmouth.uk.ibm.com X-IBM-MailFrom: borntraeger@de.ibm.com X-IBM-RcptTo: linux-arch@vger.kernel.org;linux-kernel@vger.kernel.org;linux-s390@vger.kernel.org Subject: Re: [PATCH/RFC 3/3] s390: query dynamic DEBUG_PAGEALLOC setting To: Joonsoo Kim , David Rientjes References: <1453799905-10941-1-git-send-email-borntraeger@de.ibm.com> <1453799905-10941-4-git-send-email-borntraeger@de.ibm.com> <20160126181903.GB4671@osiris> <20160127001918.GA7089@js1304-P5Q-DELUXE> <20160127005920.GB7089@js1304-P5Q-DELUXE> Cc: Heiko Carstens , linux-kernel@vger.kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, x86@kernel.org From: Christian Borntraeger Message-ID: <56A878CF.7090507@de.ibm.com> Date: Wed, 27 Jan 2016 08:59:11 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0 MIME-Version: 1.0 In-Reply-To: <20160127005920.GB7089@js1304-P5Q-DELUXE> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16012707-0021-0000-0000-00001FF3267C Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/27/2016 01:59 AM, Joonsoo Kim wrote: > On Tue, Jan 26, 2016 at 04:36:11PM -0800, David Rientjes wrote: >> On Wed, 27 Jan 2016, Joonsoo Kim wrote: >> >>>> I'd agree if CONFIG_DEBUG_PAGEALLOC only did anything when >>>> debug_pagealloc_enabled() is true, but that doesn't seem to be the case. >>>> When CONFIG_DEBUG_SLAB is enabled, for instance, CONFIG_DEBUG_PAGEALLOC >>>> also enables stackinfo storing and poisoning and it's not guarded by >>>> debug_pagealloc_enabled(). >>>> >>>> It seems like CONFIG_DEBUG_PAGEALLOC enables debugging functionality >>>> outside the scope of the debug_pagealloc=on kernel parameter, so >>>> DEBUG_PAGEALLOC(disabled) actually does mean something. >>> >>> Hello, David. >>> >>> I tried to fix CONFIG_DEBUG_SLAB case on 04/16 of following patchset. >>> >>> http://thread.gmane.org/gmane.linux.kernel.mm/144527 >>> >>> I found that there are more sites to fix but not so many. >>> We can do it. >>> >> >> For the slab case, sure, this can be fixed, but there is other code that >> uses CONFIG_DEBUG_PAGEALLOC to suggest debugging is always enabled and is >> indifferent to debug_pagealloc_enabled(). I find this in powerpc and >> sparc arch code as well as generic vmalloc code. > > Yes, I also found it. > >> >> If we can convert existing users that only check for >> CONFIG_DEBUG_PAGEALLOC to rather check for debug_pagealloc_enabled() and >> agree that it is only enabled for debug_pagealloc=on, then this would seem >> fine. However, I think we should at least consult with those users before >> removing an artifact from the kernel log that could be useful in debugging >> why a particular BUG() happened. > > Yes, at least, non-architecture dependent code (vmalloc, SLAB, SLUB) should > be changed first. If Christian doesn't mind, I will try to fix above 3 > things. Ok. So I will change this as Heiko and Thomas suggested for s390 and x86 and resend these 3 patches. Feel free to work on the other areas. Christian