Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756357Ab3G3OaE (ORCPT ); Tue, 30 Jul 2013 10:30:04 -0400 Received: from cantor2.suse.de ([195.135.220.15]:40971 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755300Ab3G3OaC (ORCPT ); Tue, 30 Jul 2013 10:30:02 -0400 Date: Tue, 30 Jul 2013 16:29:57 +0200 From: Michal Hocko To: Peter Zijlstra Cc: Minchan Kim , "Aneesh Kumar K.V" , Dave Jones , Linux Kernel , linux-mm@kvack.org, Rik van Riel , KAMEZAWA Hiroyuki , Hillf Danton , Andrew Morton Subject: Re: hugepage related lockdep trace. Message-ID: <20130730142957.GG15847@dhcp22.suse.cz> References: <20130717153223.GD27731@redhat.com> <20130718000901.GA31972@blaptop> <87hafrdatb.fsf@linux.vnet.ibm.com> <20130719001303.GB23354@blaptop> <20130723140120.GG8677@dhcp22.suse.cz> <20130724024428.GA14795@bbox> <20130725133040.GI12818@dhcp22.suse.cz> <20130729082453.GB29129@bbox> <20130729145308.GG4678@dhcp22.suse.cz> <20130729152001.GC22156@laptop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130729152001.GC22156@laptop.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1371 Lines: 41 On Mon 29-07-13 17:20:01, Peter Zijlstra wrote: > On Mon, Jul 29, 2013 at 04:53:08PM +0200, Michal Hocko wrote: > > Peter, for you context the lockdep splat has been reported > > here: https://lkml.org/lkml/2013/7/17/381 > > > > Minchan has proposed to workaround it by using SINGLE_DEPTH_NESTING > > https://lkml.org/lkml/2013/7/23/812 > > > > my idea was to use a separate class key for hugetlb as it is quite > > special in many ways: > > https://lkml.org/lkml/2013/7/25/277 > > > > What is the preferred way of fixing such an issue? > > The class is the safer annotation. OK, I will use the class then. It should prevent other false positives AFAIU. > That said; it is a rather horrible issue any which way. This PMD sharing > is very unique to hugetlbfs (also is that really worth the effort these > days?) and it will make it impossible to make hugetlbfs swappable. No idea. > The other solution is to make the pmd allocation GFP_NOFS. That would be just papering over the lockdep limitation. So I would rather stick with something lockdep specific. I will cook up a patch. Thanks! -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/