*** This bug is a security vulnerability ***
Private security bug reported:
Description
-----------
Dell OptiPlex 7780 AIO (All-in-One), BIOS 1.46.0 (Dell build date 2026-08-28),
Ubuntu 24.04.5 LTS.
The kernel reports
workqueue: acpi_os_execute_deferred hogged CPU for >10000us N times,
consider switching to WQ_UNBOUND
continuously on EVERY boot, on all installed kernel series (6.8.0-142, -146,
-147), at least since 2026-09-28 (start of journal retention) and on BOTH the
previous BIOS version and the current one (see BIOS timeline below). Rate is
roughly
1-2 events/minute around the clock; the cumulative counter exceeds 32,000
events per multi-week boot. The reported N doubles over time because the
kernel prints at cumulative milestones; the RATE is steady, not accelerating.
Symptom impact: normally none visible (16-core i7-10700 absorbs it), but on
2026-10-27 09:31 CET the system hard-locked ~36 minutes after boot and had to
be power-cycled (journal of that boot ends abruptly; no shutdown/initrd
records). Causality between the ACPI hogging and the lockup is UNPROVEN.
Evidence: per-boot event timeline
---------------------------------
Format: kernel | boot span | N messages | reported counts
boot 6.8.0-142 | Sep 28 11:43 - Oct 5 17:20 | 21 |
4,8,16,32,64,128,256,512,1024,2048,4096,8192,16384,32768
boot 6.8.0-146 | Oct 6 08:54 - Oct 12 18:12 | 22 |
4,8,16,32,64,128,256,512,1024,2048,4096,8192,16384
boot 6.8.0-146 | Oct 13 09:00 - Oct 13 11:22 | 8 | 4,8,16,32,64,128,256
boot 6.8.0-146 | Oct 13 11:30 - Oct 26 18:23 | 21 |
4,8,16,32,64,128,256,512,1024,2048,4096,8192,16384,32768
boot 6.8.0-147 | Oct 27 08:56 - Oct 27 09:31 | 4 | 4,8,16,32 <- LOCKED UP,
hard reset
boot 6.8.0-147 | Oct 27 09:35 - Oct 27 10:05 | 4 | 4,8,16,32 <- manual
reboot, otherwise OK
boot 6.8.0-146 | Oct 27 10:05 - (running) | 3 | 4,8,16
Last journal line before the lockup (boot of 08:56):
Oct 27 09:31:54 wb33 kernel: workqueue: acpi_os_execute_deferred hogged CPU
for >10000us 32 times, consider switching to WQ_UNBOUND
(Counter at an entirely ordinary level -> lockup cause unattributed.)
Negative findings (already checked)
-----------------------------------
- No GPE/interrupt storm: /proc/interrupts ACPI line (irq 9) nearly idle;
no GPE counter >1000 in /sys/firmware/acpi/interrupts/
- Temperatures normal at time of inspection (38-42 C, fans 1500-1600 rpm)
- No ACPI Error/AE_ exceptions except a common benign
\_SB.PCI0.PEG0.PEGP._DSM argument-type warning (NVIDIAPEG)
- No OOM kills, no hung tasks, no NVMe/ATA resets or I/O errors in journal
- i801_smbus reports "BIOS is accessing SMBus registers" each boot
(ACPI opregion on SMBus; EC/SMBus polled heavily by firmware - suspected
source of the slow AML execution)
- No firmware flashed via fwupd since 2026-10-13 (BIOS timeline: 1.46.0 was
flashed 2026-10-13 ~11:30 via fwupd/UEFI capsule after a GNOME Software
notification, automatic BIOS updates enabled). IMPORTANT: the ACPI hogging
PREDATES this flash — boots from 2026-09-28 to 2026-10-12 ran the previous
BIOS and already showed the identical behaviour (~16384-32768 cumulative
events). The double reboot on 2026-10-13 was the flash reboot, not a stall.
1.46.0 neither introduced nor changed the hogging rate.
- Machine stable for multi-week uptimes despite the constant hogging,
except the single 2026-10-27 lockup
Reproduction
------------
Just boot the machine and run:
journalctl -k -b 0 --grep hogged
Message appears within ~5 minutes of boot and continues indefinitely.
Environment
-----------
sys_vendor / product : Dell Inc. / OptiPlex 7780 AIO
board / BIOS : 0D54VK / 1.46.0 (2026-08-28), flashed 2026-10-13 ~11:30
via fwupd/UEFI capsule (GNOME Software auto-update path);
previous BIOS version unknown (fwupd 2.0.20 kept no
accessible history)
CPU : Intel Core i7-10700 (16 threads)
GPU : Intel UHD 630 + NVIDIA GTX 1650 Mobile
(proprietary "nvidia" kernel driver in use, NOT nouveau)
Kernel cmdline : ro text mem_sleep_default=deep
SecureBoot : disabled
OS : Ubuntu 24.04.5 LTS
Journal retention : since 2026-09-28
ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: linux-image-6.8.0-146-generic 6.8.0-146.146
ProcVersionSignature: Ubuntu 6.8.0-146.146-generic 6.8.12
Uname: Linux 6.8.0-146-generic x86_64
ApportVersion: 2.28.3-0ubuntu0.1
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: ubuntu:GNOME
Date: Tue Oct 27 10:40:03 2026
DistributionChannelDescriptor:
# This is the distribution channel descriptor for the OEM CDs
# For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
canonical-oem-somerville-bionic-amd64-20190418-59+beaver-osp1+X00
InstallationDate: Installed on 2022-04-01 (1670 days ago)
InstallationMedia: Ubuntu 18.04 "Bionic" - Build amd64 LIVE Binary
20190418-12:10
MachineType: Dell Inc. OptiPlex 7780 AIO
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-6.8.0-146-generic
root=UUID=f1c19294-2c59-4faf-95f8-23364e4dea6f ro text mem_sleep_default=deep
PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No
PulseAudio daemon running, or not running as session daemon.
RelatedPackageVersions:
linux-restricted-modules-6.8.0-146-generic N/A
linux-backports-modules-6.8.0-146-generic N/A
linux-firmware 20240318.git3b128b60.0ubuntu3.1
SourcePackage: linux
UpgradeStatus: Upgraded to noble on 2024-05-29 (881 days ago)
dmi.bios.date: 08/28/2026
dmi.bios.release: 1.46
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.46.0
dmi.board.name: 0D54VK
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 13
dmi.chassis.vendor: Dell Inc.
dmi.modalias:
dmi:bvnDellInc.:bvr1.46.0:bd08/28/2026:br1.46:svnDellInc.:pnOptiPlex7780AIO:pvr:rvnDellInc.:rn0D54VK:rvrA00:cvnDellInc.:ct13:cvr:sku0986:
dmi.product.family: OptiPlex
dmi.product.name: OptiPlex 7780 AIO
dmi.product.sku: 0986
dmi.sys.vendor: Dell Inc.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug noble wayland-session
** Attachment added: "4 files, (acpi table dump...)"
https://bugs.launchpad.net/bugs/2172294/+attachment/6012928/+files/wb33-acpi-evidence-20261027.tar.gz
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https://bugs.launchpad.net/bugs/2172294
Title:
Dell OptiPlex 7780 AIO: acpi_os_execute_deferred continuously hogging
CPU on every boot (BIOS 1.46.0); one hard lockup
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