linux-kernel - Re: divide error: 0000 [#1] SMP in task_numa_migrate

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Date:	Tue, 17 May 2016 08:01:35 +0200
From:	Stefan Priebe - Profihost AG <s.priebe@...fihost.ag>
To:	Greg KH <greg@...ah.com>
Cc:	Vlastimil Babka <vbabka@...e.cz>,
	LKML <linux-kernel@...r.kernel.org>,
	Campbell Steven <casteven@...il.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	linux-mm@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Rik van Riel <riel@...hat.com>
Subject: Re: divide error: 0000 [#1] SMP in task_numa_migrate -
 handle_mm_fault vanilla 4.4.6

Am 21.03.2016 um 14:38 schrieb Greg KH:
> 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 :)

Today i got another report from: casteven (at) gmail.com having the same
issue. I wasn't able to figure out which of those 9 patches helps - i
still can just tell that it does not happen with this series on top of 4.4.

Stefan