From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta7.messagelabs.com (mail6.bemta7.messagelabs.com [216.82.255.55]) by kanga.kvack.org (Postfix) with ESMTP id A02526B0169 for ; Wed, 3 Aug 2011 09:28:44 -0400 (EDT) Date: Wed, 3 Aug 2011 14:28:39 +0100 From: Mel Gorman Subject: Re: [PATCH] ARM: sparsemem: Enable CONFIG_HOLES_IN_ZONE config option for SparseMem and HAS_HOLES_MEMORYMODEL for linux-3.0. Message-ID: <20110803132839.GG19099@suse.de> References: <20110803110555.GD19099@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Kautuk Consul Cc: Russell King , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org On Wed, Aug 03, 2011 at 05:59:03PM +0530, Kautuk Consul wrote: > Hi Mel, > > Sorry for the formatting. > > I forgot to include the following entire backtrace: > #> cp test_huge_file nfsmnt > kernel BUG at mm/page_alloc.c:849! > Unable to handle kernel NULL pointer dereference at virtual address 00000000 > pgd = ce9f0000 > > Backtrace: > [] (__bug+0x0/0x30) from [] > (move_freepages_block+0xd4/0x158) It's still horribly mangled and pretty much unreadable but at least we know where the bug is hitting. > > > Since I was testing on linux-2.6.35.9, line 849 in page_alloc.c is the > same line as you have mentioned: > BUG_ON(page_zone(start_page) != page_zone(end_page)) > > I reproduce this crash by altering the memory banks' memory ranges > such that they are not aligned to the SECTION_SIZE_BITS size. How are you altering the ranges? Are you somehow breaking the checks based on the information in stuct zone that is in move_freepages_block()? It no longer seems like a punching-hole-in-memmap problem. Can you investigate how and why the range of pages passed in to move_freepages() belong to different zones? Thanks. -- Mel Gorman 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org