From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx168.postini.com [74.125.245.168]) by kanga.kvack.org (Postfix) with SMTP id 7BC8290001B for ; Thu, 13 Jun 2013 09:29:13 -0400 (EDT) Date: Thu, 13 Jun 2013 15:29:08 +0200 From: Michal Hocko Subject: Re: mem_cgroup_page_lruvec: BUG: unable to handle kernel NULL pointer dereference at 00000000000001a8 Message-ID: <20130613132908.GC23070@dhcp22.suse.cz> References: <20130613120248.GB23070@dhcp22.suse.cz> <51B9B5BC.4090702@nod.at> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51B9B5BC.4090702@nod.at> Sender: owner-linux-mm@kvack.org List-ID: To: Richard Weinberger Cc: LKML , "linux-mm@kvack.org" , cgroups mailinglist , "kamezawa.hiroyu@jp.fujitsu.com" , bsingharora@gmail.com, hannes@cmpxchg.org On Thu 13-06-13 14:06:20, Richard Weinberger wrote: [...] > All code > ======== > 0: 89 50 08 mov %edx,0x8(%rax) > 3: 48 89 d1 mov %rdx,%rcx > 6: 0f 1f 40 00 nopl 0x0(%rax) > a: 49 8b 04 24 mov (%r12),%rax > e: 48 89 c2 mov %rax,%rdx > 11: 48 c1 e8 38 shr $0x38,%rax > 15: 83 e0 03 and $0x3,%eax nid = page_to_nid > 18: 48 c1 ea 3a shr $0x3a,%rdx zid = page_zonenum > 1c: 48 69 c0 38 01 00 00 imul $0x138,%rax,%rax > 23: 48 03 84 d1 e0 02 00 add 0x2e0(%rcx,%rdx,8),%rax &memcg->nodeinfo[nid]->zoneinfo[zid] > 2a: 00 > 2b:* 48 3b 58 70 cmp 0x70(%rax),%rbx <-- trapping instruction OK, so this maps to: if (unlikely(lruvec->zone != zone)) <<< lruvec->zone = zone; > [35355.883056] RSP: 0000:ffff88003d523aa8 EFLAGS: 00010002 > [35355.883056] RAX: 0000000000000138 RBX: ffff88003fffa600 RCX: ffff88003e04a800 > [35355.883056] RDX: 0000000000000020 RSI: 0000000000000000 RDI: 0000000000028500 > [35355.883056] RBP: ffff88003d523ab8 R08: 0000000000000000 R09: 0000000000000000 > [35355.883056] R10: 0000000000000000 R11: dead000000100100 R12: ffffea0000a14000 > [35355.883056] R13: ffff88003e04b138 R14: ffff88003d523bb8 R15: ffffea0000a14020 > [35355.883056] FS: 0000000000000000(0000) GS:ffff88003fd80000(0000) RAX (lruvec) is obviously incorrect and it doesn't make any sense. rax should contain an address at an offset from ffff88003e04a800 But there is 0x138 there instead. Is this easily reproducible? Could you configure kdump. -- 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