From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f173.google.com (mail-ig0-f173.google.com [209.85.213.173]) by kanga.kvack.org (Postfix) with ESMTP id 9808F6B0005 for ; Tue, 26 Jan 2016 19:59:24 -0500 (EST) Received: by mail-ig0-f173.google.com with SMTP id t15so72670901igr.0 for ; Tue, 26 Jan 2016 16:59:24 -0800 (PST) Received: from lgeamrelo11.lge.com (LGEAMRELO11.lge.com. [156.147.23.51]) by mx.google.com with ESMTPS id iq7si9065981igb.92.2016.01.26.16.59.22 for (version=TLS1 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 26 Jan 2016 16:59:23 -0800 (PST) Date: Wed, 27 Jan 2016 09:59:21 +0900 From: Joonsoo Kim Subject: Re: [PATCH/RFC 3/3] s390: query dynamic DEBUG_PAGEALLOC setting Message-ID: <20160127005920.GB7089@js1304-P5Q-DELUXE> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: Heiko Carstens , Christian Borntraeger , 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 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. Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org