Kernel warning on driver-domain

["J. Roeleveld" <joost@xxxxxxxxxxxx>]

Hi,

I am getting semi-regular warnings in the dmesg about block devices shared to 
other Domains from a driver-domain.

The dmesg/kernel trace is at the bottom of the email.
All the traces show the same "call trace" and most of the numbers looks similar.
It's always a different domain and xvda-device that is listed.

Versions (Dom0 and driver domain are kept at same versions)
Kernel: 5.10.52
Xen: 4.14.2

Apart from these warning, I do not see any issues. The domains are running 
stable, no messages in the logs.

In this particular one, the domain is practically idle, xvda2 is for the swap 
partition, which isn't actually used.

In previous ones, similarly only the dmesg message on the driver domain, all 
other domains don't show anything.
There was a scrub running on a different pool, which finished at 17:19:35. 
(Nearly 30 minutes before).

I tried to google for these, but apart from a few possible matches with much 
older kernels, I couldn't find anything related.

====
[Fri Sep  3 17:48:01 2021] ------------[ cut here ]------------ 
[Fri Sep  3 17:48:01 2021] WARNING: CPU: 0 PID: 27163 at kernel/kthread.c:83 
to_kthread+0x6/0x10 
[Fri Sep  3 17:48:01 2021] Modules linked in: rpcsec_gss_krb5 
target_core_iblock iscsi_target_mod target_core_mod xt_recent ipt_REJECT 
nf_reject_ipv4 xt_multiport xt_tcpudp xt_conntrack xt_hashlimit xt_addrtype 
xt_mark iptable_mangle iptable_nat iptable_raw n
fnetlink_log xt_NFLOG nf_log_ipv4 nf_log_common xt_LOG nf_nat 
nf_conntrack_netlink nf_conntrack nf_defrag_ipv4 nfnetlink iptable_filter 
ip_tables x_tables dm_queue_length zfs(PO) zunicode(PO) zzstd(O) zlua(O) 
zcommon(PO) znvpair(PO) zavl(PO) icp(PO) spl(O) cr
ct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel mpt3sas 
aesni_intel scsi_transport_sas 
[Fri Sep  3 17:48:01 2021] CPU: 0 PID: 27163 Comm: 18.xvda2-0 Tainted: P        
W  O      5.10.52-gentoo-generic #1 
[Fri Sep  3 17:48:01 2021] RIP: e030:to_kthread+0x6/0x10 
[Fri Sep  3 17:48:01 2021] Code: 99 22 e3 81 e8 6f 73 3c 00 48 98 c3 e8 82 24 
f9 ff 66 90 c3 e8 5a 24 f9 ff 66 90 c3 e8 8e 18 02 00 66 90 c3 f6 47 26 20 75 
02 <0f> 0b 48 8b 87 a8 04 00 00 c3 e8 eb ff ff ff 48 8b 40 18 c3 65 48 
[Fri Sep  3 17:48:01 2021] RSP: e02b:ffffc90020267b90 EFLAGS: 00010046 
[Fri Sep  3 17:48:01 2021] RAX: ffff889886e2a2c0 RBX: ffffc90020267c10 RCX: 
ffff889886f00000 
[Fri Sep  3 17:48:01 2021] RDX: 0000000000000000 RSI: ffffc90020267c10 RDI: 
ffff889140a38ec0 
[Fri Sep  3 17:48:01 2021] RBP: ffff889140a38ec0 R08: 000188e909deff76 R09: 
0000000000000040 
[Fri Sep  3 17:48:01 2021] R10: 0000000000000004 R11: 0000000000000001 R12: 
0000000000000000 
[Fri Sep  3 17:48:01 2021] R13: 0000000000000000 R14: 0000000000000000 R15: 
ffff889140a38f68 
[Fri Sep  3 17:48:01 2021] FS:  0000000000000000(0000) 
GS:ffff889886e00000(0000) knlGS:0000000000000000 
[Fri Sep  3 17:48:01 2021] CS:  10000e030 DS: 0000 ES: 0000 CR0: 
0000000080050033 
[Fri Sep  3 17:48:01 2021] CR2: 000055e9dec50978 CR3: 000000011ed0c000 CR4: 
0000000000050660 
[Fri Sep  3 17:48:01 2021] Call Trace: 
[Fri Sep  3 17:48:01 2021]  kthread_is_per_cpu+0x5/0x16 
[Fri Sep  3 17:48:01 2021]  can_migrate_task+0x65/0x17a 
[Fri Sep  3 17:48:01 2021]  load_balance+0x3e8/0x83e 
[Fri Sep  3 17:48:01 2021]  newidle_balance+0x1d0/0x2a7 
[Fri Sep  3 17:48:01 2021]  pick_next_task_fair+0x196/0x1f7 
[Fri Sep  3 17:48:01 2021]  __schedule+0x1ab/0x515 
[Fri Sep  3 17:48:01 2021]  ? _raw_spin_unlock_irqrestore+0xd/0xe 
[Fri Sep  3 17:48:01 2021]  ? __mod_timer+0x21f/0x246 
[Fri Sep  3 17:48:01 2021]  schedule+0x73/0x99 
[Fri Sep  3 17:48:01 2021]  schedule_timeout+0x9e/0xd7 
[Fri Sep  3 17:48:01 2021]  ? __next_timer_interrupt+0xe3/0xe3 
[Fri Sep  3 17:48:01 2021]  xen_blkif_schedule+0x251/0xb5e 
[Fri Sep  3 17:48:01 2021]  ? __wake_up_locked_sync_key+0x15/0x15 
[Fri Sep  3 17:48:01 2021]  ? __schedule+0x4f2/0x515 
[Fri Sep  3 17:48:01 2021]  ? arch_local_irq_disable+0x5/0x8 
[Fri Sep  3 17:48:01 2021]  ? arch_local_irq_save+0x11/0x17 
[Fri Sep  3 17:48:01 2021]  ? xen_blkif_be_int+0x22/0x22 
[Fri Sep  3 17:48:01 2021]  kthread+0xea/0xef 
[Fri Sep  3 17:48:01 2021]  ? kthread_mod_delayed_work+0xb8/0xb8 
[Fri Sep  3 17:48:01 2021]  ret_from_fork+0x22/0x30 
[Fri Sep  3 17:48:01 2021] ---[ end trace 9280d21445c4f71b ]---
====