From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx106.postini.com [74.125.245.106]) by kanga.kvack.org (Postfix) with SMTP id C2D646B0031 for ; Tue, 30 Jul 2013 10:30:01 -0400 (EDT) Date: Tue, 30 Jul 2013 16:29:57 +0200 From: Michal Hocko 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> Sender: owner-linux-mm@kvack.org List-ID: 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 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, 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