From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757196AbYEMSkZ (ORCPT ); Tue, 13 May 2008 14:40:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753928AbYEMSkM (ORCPT ); Tue, 13 May 2008 14:40:12 -0400 Received: from rv-out-0506.google.com ([209.85.198.238]:9320 "EHLO rv-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753656AbYEMSkK (ORCPT ); Tue, 13 May 2008 14:40:10 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:sender:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references:x-google-sender-auth; b=ZZpRe20+EKDgJ1KQdpbUVgChJ61qxq8FTTJT9IKaraVfZiOo+gt/twfJo1dzlCc2PlpmiHIoXSdLNx7N3DbhUmp8OTjxnPECHuoxM0zJWvGgSTRWgMJrEIkmG1RiWap6GtExl9QwyhldhvLORfVkdT5/Zu7L7NEq0BwNxhvxXEQ= Message-ID: <84144f020805131140s233090e5v4f77c4853a91f2ec@mail.gmail.com> Date: Tue, 13 May 2008 21:40:08 +0300 From: "Pekka Enberg" To: "Benny Halevy" Subject: Re: [PATCH] SLUB: clear c->freelist in __slab_alloc()/load_freelist:/SlabDebug path Cc: "Christoph Lameter" , "Linux Kernel" In-Reply-To: <4828A940.2090604@panasas.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <4828A940.2090604@panasas.com> X-Google-Sender-Auth: 15838802c15ef678 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Benny, On Mon, May 12, 2008 at 11:32 PM, Benny Halevy wrote: > In the __slab_alloc()/load_freelist:/SlabDebug(c->page) path we only > use the object at the head of c->page->freelist > and the tail goes back to c->page->freelist. > We then set c->node = -1 to force __slab_alloc in next allocation. > c->freelist therefore needs to be cleared as it is invalid at this point. But for debug pages, we never load c->page->freelist to c->freelist so it should always be NULL. > Signed-off-by: Benny Halevy > --- > mm/slub.c | 1 + > 1 files changed, 1 insertions(+), 0 deletions(-) > > Hit while running cthon04 test from an IBM AIX client > against my nfs41 tree. > > Stack trace excerpt: > > May 12 11:18:19 client kernel: general protection fault: 0000 [2] SMP > May 12 11:18:19 client kernel: CPU 3 > May 12 11:18:19 client kernel: Modules linked in: panfs(P) nfsd auth_rpcgss exportfs autofs4 hidp nfs lockd nfs_acl fuse rfcomm l2cap bluetooth sunrpc nf_conntrack_netbios_ns nf_conntrack_ipv4 ipt_REJECT iptable_filter ip_tables nf_conntrack_ipv6 xt_state nf_conntrack xt_tcpudp ip6t_ipv6header ip6t_REJECT ip6table_filter ip6_tables x_tables ipv6 dm_multipath video output sbs sbshc battery ac e1000e i5000_edac iTCO_wdt iTCO_vendor_support i2c_i801 edac_core button sr_mod pcspkr i2c_core sg cdrom floppy dm_snapshot dm_zero dm_mirror dm_mod ata_piix libata shpchp pci_hotplug mptsas mptscsih mptbase scsi_transport_sas sd_mod scsi_mod ext3 jbd mbcache ehci_hcd ohci_hcd uhci_hcd [last unloaded: microcode] > May 12 11:18:19 client kernel: Pid: 2815, comm: nfsd Tainted: P D 2.6.25-nfs41 #2 > May 12 11:18:19 client kernel: RIP: 0010:[] [] kmem_cache_alloc+0x3d/0x65 > May 12 11:18:19 client kernel: RSP: 0018:ffff8104212c3de0 EFLAGS: 00010006 > May 12 11:18:19 client kernel: RAX: 0000000000000000 RBX: 0000000000000246 RCX: ffffffff883546df > May 12 11:18:19 client kernel: RDX: 3200100010100000 RSI: 00000000000080d0 RDI: ffffffff813eadb8 > May 12 11:18:19 client kernel: RBP: ffff810001029e60 R08: 0000000000000000 R09: ffff8103f118d130 > May 12 11:18:19 client kernel: R10: ffff81041b076018 R11: ffffffff8826c313 R12: 00000000000080d0 > May 12 11:18:19 client kernel: R13: ffff8104211aa000 R14: ffff81041b076000 R15: ffff8104239c8000 > May 12 11:18:19 client kernel: FS: 00007f08fb8626f0(0000) GS:ffff81042fc02e80(0000) knlGS:0000000000000000 > May 12 11:18:19 client kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b > May 12 11:18:19 client kernel: CR2: 00007fdaf41cf030 CR3: 0000000420827000 CR4: 00000000000006e0 > May 12 11:18:19 client kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > May 12 11:18:19 client kernel: DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 > May 12 11:18:19 client kernel: Process nfsd (pid: 2815, threadinfo ffff8104212c2000, task ffff81042381c940) > May 12 11:18:19 client kernel: Stack: ffff8104211ab000 ffff8103f118d000 0000000022270000 ffffffff883546df > May 12 11:18:19 client kernel: ffffffff88373cb8 0000000000000000 ffff8103f118d130 ffff8104239c8000 > May 12 11:18:19 client kernel: ffffffff88373cb8 000000000000001c ffff81041b076018 ffff81041b076000 > May 12 11:18:19 client kernel: Call Trace: > May 12 11:18:19 client kernel: [] ? :nfsd:nfsd4_proc_compound+0xa9/0x3f6 > May 12 11:18:19 client kernel: [] ? :nfsd:nfsd_dispatch+0xde/0x1b6 > May 12 11:18:19 client kernel: [] ? :sunrpc:svc_process_common+0x2e8/0x5a9 > May 12 11:18:19 client kernel: [] ? :nfsd:nfsd+0x0/0x2b4 > May 12 11:18:19 client kernel: [] ? :sunrpc:svc_process+0x127/0x13d > May 12 11:18:19 client kernel: [] ? :nfsd:nfsd+0x19d/0x2b4May 12 11:18:19 client kernel: [] ? child_rip+0xa/0x12 > May 12 11:18:19 client kernel: [] ? :nfsd:nfsd+0x0/0x2b4 > May 12 11:18:19 client last message repeated 2 times > May 12 11:18:19 client kernel: [] ? child_rip+0x0/0x12 > May 12 11:18:19 client kernel: > May 12 11:18:19 client kernel: > May 12 11:18:19 client kernel: Code: 25 24 00 00 00 48 98 48 8b ac c7 d8 02 00 00 48 8b 55 00 48 85 d2 75 10 83 ca ff 49 89 e8 e8 7e f8 ff ff 48 89 c2 eb 0b 8b 45 14 <48> 8b 04 c2 48 89 45 00 53 9d 66 45 85 e4 79 10 48 85 d2 74 0b > May 12 11:18:19 client kernel: RIP [] kmem_cache_alloc+0x3d/0x65 > May 12 11:18:19 client kernel: RSP > May 12 11:18:19 client kernel: ---[ end trace 9b6f5806f68a2b8c ]--- > > $ grep SL.B .config > CONFIG_SLUB_DEBUG=y > # CONFIG_SLAB is not set > CONFIG_SLUB=y > # CONFIG_SLOB is not set > CONFIG_SLABINFO=y > # CONFIG_SLUB_DEBUG_ON is not set > # CONFIG_SLUB_STATS is not set > > diff --git a/mm/slub.c b/mm/slub.c > index a505a82..0d1d820 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -1606,6 +1606,7 @@ debug: > if (!alloc_debug_processing(s, c->page, object, addr)) > goto another_slab; > > + c->freelist = NULL; > c->page->inuse++; > c->page->freelist = object[c->offset]; > c->node = -1; Looking at this, we're oopsing at: 0: 48 8b 04 c2 mov (%rdx,%rax,8),%rax where rdx is c->freelist and rax c->offset. The the value for c->freelist ("3200100010100000") doesn't make much sense. Furthermore, we never if this really were a bug in __slab_alloc() shouldn't we be hitting it more often? How did you make SLUB hit the debug path since you have CONFIG_SLUB_DEBUG_ON disabled? Pekka