Re: divide error: 0000 [#1] SMP in task_numa_migrate - handle_mm_fault vanilla 4.4.6

From: Vlastimil Babka
Date: Sat Mar 19 2016 - 18:27:18 EST


On 03/17/2016 07:45 PM, Greg KH wrote:
On Thu, Mar 17, 2016 at 07:38:03PM +0100, Stefan Priebe wrote:
Hi,

while running qemu 2.5 on a host running 4.4.6 the host system has crashed
(load > 200) 3 times in the last 3 days.

Always with this stack trace: (copy left here:
http://pastebin.com/raw/bCWTLKyt)

[69068.874268] divide error: 0000 [#1] SMP
[69068.875242] Modules linked in: ebtable_filter ebtables ip6t_REJECT
nf_reject_ipv6 nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_filter ip6_tables
ipt_REJECT nf_reject_ipv4 xt_physdev xt_comment nf_conntrack_ipv4
nf_defrag_ipv4 xt_tcpudp xt_mark xt_set xt_addrtype xt_conntrack
nf_conntrack ip_set_hash_net ip_set vhost_net tun vhost macvtap macvlan
kvm_intel nfnetlink_log kvm nfnetlink irqbypass netconsole dlm xt_multiport
iptable_filter ip_tables x_tables iscsi_tcp libiscsi_tcp libiscsi
scsi_transport_iscsi nfsd auth_rpcgss oid_registry bonding coretemp 8021q
garp fuse i2c_i801 i7core_edac edac_core i5500_temp button btrfs xor
raid6_pq dm_mod raid1 md_mod usb_storage ohci_hcd bcache sg usbhid sd_mod
ata_generic uhci_hcd ehci_pci ehci_hcd usbcore ata_piix usb_common igb
i2c_algo_bit mpt3sas raid_class ixgbe scsi_transport_sas i2c_core mdio ptp
pps_core
[69068.895604] CPU: 14 PID: 6673 Comm: ceph-osd Not tainted 4.4.6+7-ph #1
[69068.897052] Hardware name: Supermicro X8DT3/X8DT3, BIOS 2.1 03/17/2012
[69068.898578] task: ffff880fc7f28000 ti: ffff880fda2c4000 task.ti:
ffff880fda2c4000
[69068.900377] RIP: 0010:[<ffffffff860b372c>] [<ffffffff860b372c>]
task_h_load+0xcc/0x100

decodecode says:

27: 48 83 c1 01 add $0x1,%rcx
2b:* 48 f7 f1 div %rcx <-- trapping instruction

This suggests the CONFIG_FAIR_GROUP_SCHED version of task_h_load:

update_cfs_rq_h_load(cfs_rq);
return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
cfs_rq_load_avg(cfs_rq) + 1);

So the load avg is -1, thus after adding 1 we get division by 0, huh?

[69068.961763] RSP: 0000:ffff880fda2c7b50 EFLAGS: 00010257
[69069.023910] RAX: 0000000000000000 RBX: ffff880fda2c7c10 RCX:
0000000000000000
[69069.085953] RDX: 0000000000000000 RSI: 0000000000000001 RDI:
ffff880fc7f28000
[69069.151731] RBP: ffff880fda2c7bc8 R08: 00000001041955df R09:
ffff880fffd153f8
[69069.213757] R10: 0000000000000009 R11: 0000000000000193 R12:
ffff881f6832c780
[69069.274271] R13: ffff88203fc35380 R14: 0000000000000007 R15:
00000000000000b6
[69069.334727] FS: 00007f578a3fb700(0000) GS:ffff880fffd00000(0000)
knlGS:0000000000000000
[69069.396435] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[69069.458522] CR2: 00007f5784f18468 CR3: 0000001fe9738000 CR4:
00000000000026e0
[69069.520799] Stack:
[69069.581430] ffffffff860b6855 ffff880fda2c7b78 0000000000000000
0000000000000005
[69069.642629] ffff880fffd00000 0000000000000015 fffffffffffffe7d
0000000000000015
[69069.702815] 0000000000015380 ffff880fda2c7bc8 ffff880fc7f28000
00000000000001e9
[69069.761881] Call Trace:
[69069.819883] [<ffffffff860b6855>] ? task_numa_find_cpu+0x225/0x670
[69069.878368] [<ffffffff860b79f0>] task_numa_migrate+0x550/0x950
[69069.936059] [<ffffffff863d9138>] ? find_next_bit+0x18/0x20
[69069.993262] [<ffffffff860b7e6d>] numa_migrate_preferred+0x7d/0x90
[69070.050528] [<ffffffff860b89a5>] task_numa_fault+0x7c5/0xaa0
[69070.106544] [<ffffffff861a2c0b>] ? mpol_misplaced+0x16b/0x1b0
[69070.163705] [<ffffffff8618104e>] __handle_mm_fault+0x9ae/0x11f0
[69070.220013] [<ffffffff865e4c52>] ? inet_recvmsg+0x72/0x90
[69070.276558] [<ffffffff8655240b>] ? SYSC_recvfrom+0x12b/0x170
[69070.332283] [<ffffffff8618196f>] handle_mm_fault+0xdf/0x180
[69070.388515] [<ffffffff8604f324>] __do_page_fault+0x164/0x380
[69070.443897] [<ffffffff860b25c3>] ? account_user_time+0x73/0x80
[69070.498534] [<ffffffff860b2b3e>] ? vtime_account_user+0x4e/0x70
[69070.552598] [<ffffffff8604f5a7>] do_page_fault+0x37/0x90
[69070.605960] [<ffffffff86002a23>] ? syscall_return_slowpath+0x83/0xf0
[69070.660705] [<ffffffff866b32f8>] page_fault+0x28/0x30
[69070.715707] Code: 86 b8 00 00 00 48 89 86 b0 00 00 00 48 85 c9 75 ca 49
8b 81 b0 00 00 00 49 8b 49 78 31 d2 48 0f af 87 d8 01 00 00 5d 48 83 c1 01
<48> f7 f1 c3 4c 89 ce 48 8b 8e c0 00 00 00 48 8b 46 78 4c 89 86
[69070.835144] RIP [<ffffffff860b372c>] task_h_load+0xcc/0x100
[69070.894095] RSP <ffff880fda2c7b50>
[69070.953213] ---[ end trace 8d6f449a03dacfd4 ]---

Would be nice if we can fix this in 4.4?

Does this also happen in 4.5? Did this work on 4.4.5? Some previous
release? If you can find the offending patch using 'git bisect', that
would be great.

thanks,

greg k-h

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