Public bug reported:
Summary
-------
After a kernel update from 6.8.0-111-generic to 6.8.0-117-generic on Ubuntu
24.04 (noble), a USB-attached 4-bay DAS enclosure (TerraMaster D4-320, ASMedia
174c:235c bridges behind a Realtek 0bda:0423 hub) entered a continuous
xhci_hcd reset loop. Booting back into 6.8.0-111-generic on identical hardware
completely resolves the issue. This appears to be a regression introduced
somewhere in the 6.8.0-112/-114/-116/-117 range.
Impact
------
On 6.8.0-117, one downstream bay resets roughly 1.5 times per second
continuously, even with the array idle and no I/O queued. Under write load the
resets cause I/O timeouts (-110/DID_ERROR), failed writes (-28 / ENOSPC in the
write path due to stalled drains), and XFS writeback errors. Left running, this
risks filesystem corruption. The drives themselves are healthy (SMART PASSED,
zero reallocated/pending/uncorrectable sectors, zero UDMA CRC errors).
Reproducibility
---------------
100% reproducible across multiple cold boots:
- 6.8.0-117-generic: ~280-600 reset events within the first few minutes of
uptime, drives idle, array deactivated. Reset count climbs continuously.
- 6.8.0-111-generic: zero reset events. Bus completely stable, including
under sustained heavy write load (24/7 NVR workload, ~14 video streams).
Same enclosure, same USB-C cable, same drives, same port. Only the kernel
version differs.
Hardware
--------
Host USB: xHCI (Bus 004, 10 Gbit root hub)
Enclosure: TerraMaster D4-320
- Internal hub: Realtek 0bda:0423 (4-Port USB 3.2 Hub)
- 4x bridge: ASMedia Technology Inc. TDAS, 174c:235c, bcdDevice 1.00
Kernel applies these quirks automatically for 174c:235c:
"UAS is ignored for this device, using usb-storage instead"
"Quirks match for vid 174c pid 235c: 800000" (US_FL_NO_REPORT_OPCODES)
Drives: 2x Seagate Exos 22TB + 2x 12TB, LVM RAID1, XFS.
Representative dmesg (6.8.0-117, drives idle)
---------------------------------------------
usb 4-2.1: reset SuperSpeed Plus Gen 2x1 USB device number 4 using xhci_hcd
usb 4-2.1: reset SuperSpeed Plus Gen 2x1 USB device number 4 using xhci_hcd
(repeating ~1.5x/sec continuously)
Under load it escalates to:
sd 4:0:0:0: [sdc] tag#0 FAILED Result: hostbyte=DID_ERROR driverbyte=DRIVER_OK
I/O error, dev sdc, sector ... op 0x1:(WRITE)
dm-5: writeback error on inode ...
Workaround
----------
Boot 6.8.0-111-generic and pin it (apt-mark hold). Stable indefinitely.
Notes for triage
----------------
The reset loop occurs at the xhci_hcd layer with the device on the conservative
usb-storage driver (UAS already disabled by quirk), so this is not a UAS-path
issue. The regression window is 6.8.0-112 through -117. Suspect area: xHCI
transfer-event / endpoint-reset handling or link power management changes
backported into the noble 6.8 tree in that window. Happy to bisect or test
candidate kernels if useful.
ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: linux-image-6.8.0-111-generic 6.8.0-111.111
ProcVersionSignature: Ubuntu 6.8.0-111.111-generic 6.8.12
Uname: Linux 6.8.0-111-generic x86_64
AlsaVersion: Advanced Linux Sound Architecture Driver Version
k6.8.0-111-generic.
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay'
ApportVersion: 2.28.1-0ubuntu3.8
Architecture: amd64
ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord'
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/by-path',
'/dev/snd/controlC0', '/dev/snd/hwC0D2', '/dev/snd/hwC0D0',
'/dev/snd/pcmC0D9p', '/dev/snd/pcmC0D8p', '/dev/snd/pcmC0D7p',
'/dev/snd/pcmC0D3p', '/dev/snd/pcmC0D2c', '/dev/snd/pcmC0D0c',
'/dev/snd/pcmC0D0p', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
CRDA: N/A
Card0.Amixer.info: Error: [Errno 2] No such file or directory: 'amixer'
Card0.Amixer.values: Error: [Errno 2] No such file or directory: 'amixer'
CasperMD5CheckResult: pass
CurrentDmesg: Error: command ['dmesg'] failed with exit code 1: dmesg: read
kernel buffer failed: Operation not permitted
Date: Wed May 20 09:20:05 2026
InstallationDate: Installed on 2026-03-01 (80 days ago)
InstallationMedia: Ubuntu-Server 24.04.4 LTS "Noble Numbat" - Release amd64
(20260210)
IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig'
MachineType: AZW EQ
ProcEnviron:
LANG=en_US.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
ProcFB:
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-6.8.0-111-generic
root=/dev/mapper/ubuntu--vg-ubuntu--lv ro usb-storage.quirks=174c:235c:u
RelatedPackageVersions:
linux-restricted-modules-6.8.0-111-generic N/A
linux-backports-modules-6.8.0-111-generic N/A
linux-firmware 20240318.git3b128b60-0ubuntu2.27
RfKill: Error: [Errno 2] No such file or directory: 'rfkill'
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
acpidump:
dmi.bios.date: 07/21/2025
dmi.bios.release: 5.27
dmi.bios.vendor: American Megatrends International, LLC.
dmi.bios.version: EQI12D405
dmi.board.asset.tag: Default string
dmi.board.name: EQ
dmi.board.vendor: AZW
dmi.board.version: Default string
dmi.chassis.asset.tag: Default string
dmi.chassis.type: 3
dmi.chassis.vendor: Default string
dmi.chassis.version: Default string
dmi.modalias:
dmi:bvnAmericanMegatrendsInternational,LLC.:bvrEQI12D405:bd07/21/2025:br5.27:svnAZW:pnEQ:pvrDefaultstring:rvnAZW:rnEQ:rvrDefaultstring:cvnDefaultstring:ct3:cvrDefaultstring:skuDefaultstring:
dmi.product.family: Default string
dmi.product.name: EQ
dmi.product.sku: Default string
dmi.product.version: Default string
dmi.sys.vendor: AZW
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug noble
--
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https://bugs.launchpad.net/bugs/2153431
Title:
xhci_hcd: continuous SuperSpeed USB resets with ASMedia 174c:235c
(TerraMaster D4-320) on 6.8.0-117, regression from 6.8.0-111
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