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

[Greg KH <greg@kroah.com>]

On Mon, Mar 21, 2016 at 11:52:23AM +0100, Stefan Priebe - Profihost AG wrote:
> 
> Am 20.03.2016 um 22:41 schrieb Greg KH:
> > On Sun, Mar 20, 2016 at 10:27:23PM +0100, Stefan Priebe wrote:
> >>
> >> Am 19.03.2016 um 23:26 schrieb Vlastimil Babka:
> >>> 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?
> >>
> >> Yes CONFIG_FAIR_GROUP_SCHED is set. I cherry picked now all those commits up
> >> to 4.5 for fair.c:
> >> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/log/kernel/sched/fair.c?h=v4.5
> >>
> >> It didn't happen again with v4.4.6 + 4.5 patches for fair.c
> > 
> > Ok, that's a lot of patches, how about figuring out which single patch,
> > or shortest number of patches, makes things work again?
> 
> will do so but it seems most out of those 9 patches are based on each
> other. So it wouldn't be easy.

Worst case, we take all 9.  Best case, we only need one :)

thanks,

greg k-h

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