[Xen-devel] Kernel trace when using xl block-attach - 4.14.25

[Steven Haigh <netwiz@xxxxxxxxx>]

Hi all,

I've noticed recently that once every now and again I get a kernel traceback 
when attaching a drive to a DomU.

The drive in question is attached to the system via eSATA, opened via 
cryptsetup, then added to the DomU. When this crash occurs, any process trying 
to access either the /dev/mapper entry, or the DomU accessing the associated 
block device will hang and never come back.

The only real resolution is to forcefully destroy the DomU (which fails) and 
then eventually hit the reset button on the Dom0.

The trace from dmesg is as follows:
[504869.792058] xen-blkback: backend/vbd/4/51745: using 2 queues, protocol 1 
(x86_64-abi) persistent grants
[504877.624108] ------------[ cut here ]------------
[504877.624117] WARNING: CPU: 0 PID: 0 at kernel/rcu/tree.c:2725 
rcu_process_callbacks+0x495/0x4b0
[504877.624118] Modules linked in: dm_crypt algif_skcipher af_alg xt_physdev 
br_netfilter iptable_filter bridge 8021q garp stp llc btrfs zstd_decompress 
zstd_compress xxhash it87 hwmon_vid dm_mod dax raid456 async_raid6_recov 
async_memcp
y async_pq async_xor async_tx xor crct10dif_pclmul ghash_clmulni_intel pcbc 
raid6_pq aesni_intel iTCO_wdt aes_x86_64 iTCO_vendor_support crypto_simd 
glue_helper cryptd pl2303 pcspkr usbserial sg lpc_ich mei_me mei shpchp 
i2c_i801 mfd_cor
e xenfs xen_privcmd ip_tables xfs libcrc32c raid1 sd_mod i915 iosf_mbi 
i2c_algo_bit drm_kms_helper drm crc32c_intel r8169 serio_raw ahci libahci mii 
i2c_core sata_mv video xen_acpi_processor xen_pciback xen_netback xen_gntalloc 
xen_gntde
v xen_evtchn ipv6 crc_ccitt autofs4
[504877.624167] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 
4.14.25-5.el7xen.x86_64 #2
[504877.624168] Hardware name: Gigabyte Technology Co., Ltd. To be filled by 
O.E.M./Z68M-D2H, BIOS U1G 03/06/2013
[504877.624169] task: ffffffff820124c0 task.stack: ffffffff82000000
[504877.624172] RIP: e030:rcu_process_callbacks+0x495/0x4b0
[504877.624173] RSP: e02b:ffff880080203f20 EFLAGS: 00010002
[504877.624175] RAX: 0000000000000000 RBX: ffff880080222cc0 RCX: 
00000000172f7355
[504877.624177] RDX: ffffffffffffd801 RSI: ffff880080203f30 RDI: 
ffff880080222cf8
[504877.624178] RBP: ffffffff82059880 R08: 0000000000025200 R09: 
ffffffff815dc988
[504877.624179] R10: ffff880080225200 R11: ffffea0000f325c0 R12: 
ffffffff820124c0
[504877.624180] R13: 0000000000000001 R14: ffff880080222cf8 R15: 
7fffffffffffffff
[504877.624194] FS:  00007fa23850c740(0000) GS:ffff880080200000(0000) knlGS:
0000000000000000
[504877.624196] CS:  e033 DS: 0000 ES: 0000 CR0: 0000000080050033
[504877.624197] CR2: 00007f82fda14000 CR3: 0000000061b88000 CR4: 
0000000000042660
[504877.624199] Call Trace:
[504877.624203]  <IRQ>
[504877.624208]  __do_softirq+0xc8/0x26b
[504877.624211]  irq_exit+0x93/0xb0
[504877.624215]  xen_evtchn_do_upcall+0x2c/0x40
[504877.624219]  xen_do_hypervisor_callback+0x29/0x40
[504877.624221]  </IRQ>
[504877.624224] RIP: e030:xen_hypercall_sched_op+0xa/0x20
[504877.624225] RSP: e02b:ffffffff82003e90 EFLAGS: 00000246
[504877.624227] RAX: 0000000000000000 RBX: ffffffff820124c0 RCX: 
ffffffff810013aa
[504877.624228] RDX: 00000000ab50466e RSI: 0000000000000000 RDI: 
0000000000000001
[504877.624229] RBP: 0000000000000000 R08: 0000000000000002 R09: 
0000000000000000
[504877.624230] R10: 0000000000007ff0 R11: 0000000000000246 R12: 
ffffffff820124c0
[504877.624231] R13: 0000000000000000 R14: 0000000000000000 R15: 
0000000000000000
[504877.624234]  ? xen_hypercall_sched_op+0xa/0x20
[504877.624238]  ? xen_safe_halt+0xc/0x20
[504877.624240]  ? default_idle+0x18/0xf0
[504877.624242]  ? do_idle+0x164/0x1a0
[504877.624244]  ? cpu_startup_entry+0x5f/0x70
[504877.624247]  ? start_kernel+0x4e1/0x4ec
[504877.624248]  ? set_init_arg+0x55/0x55
[504877.624251]  ? xen_start_kernel+0x52e/0x538
[504877.624253] Code: 12 ff 5e 00 e9 45 fc ff ff 0f 0b e9 23 fc ff ff 0f 0b 0f 
1f 40 00 e9 f3 fc ff ff 0f 0b 66 0f 1f 84 00 00 00 00 00 e9 d5 fb ff ff <0f> 
0b 66 0f 1f 84 00 00 00 00 00 e9 d0 fd ff ff 90 66 2e 0f 1f
[504877.624290] ---[ end trace 62909e6ca83c56bf ]---

Has anyone seen this before or is aware of its cause?

-- 
Steven Haigh

📧 netwiz@xxxxxxxxx       💻 http://www.crc.id.au
📞 +61 (3) 9001 6090    📱 0412 935 897

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