Public bug reported:
My 2017 Apple iMac (iMac18,2) fails to wake reliably from suspend under
Kubuntu 26.04.
Kernels tested:
- 7.0.0-30-generic
- 7.0.0-31-generic
- 7.0.0-38-generic
Wake failures occurred with all three kernels. The detailed tests below
were performed with 7.0.0-38-generic.
Relevant hardware:
0000:08:00.0 USB controller:
Intel JHL6540 Thunderbolt 3 USB Controller (C step)
[Alpine Ridge 4C 2016] [8086:15d4], revision 02
Kernel driver: xhci_hcd
Expected result:
The system should suspend and wake reliably, including on repeated
suspend/resume cycles.
Actual result:
The system fails to wake, or unexpectedly reboots after an attempted wake. One
successful cycle does not guarantee that the next cycle works.
Tests performed:
1. Normal deep suspend:
Wake failure. Earlier diagnostic testing recorded these messages:
xhci_hcd 0000:08:00.0: not ready 32767ms after resume; waiting
xhci_hcd 0000:08:00.0: not ready 65535ms after resume; giving up
xhci_hcd 0000:08:00.0: Host halt failed, -19
xhci_hcd 0000:08:00.0: Host not accessible, reset failed.
The controller was subsequently removed, and a PCI warning reported:
xhci_hcd 0000:08:00.0: disabling already-disabled device
2. Thunderbolt driver unloaded, using deep suspend:
sudo modprobe -r thunderbolt
echo deep | sudo tee /sys/power/mem_sleep
sudo systemctl suspend
One cycle successfully resumed, with:
PM: suspend entry (deep)
xhci_hcd 0000:08:00.0: xHC error in resume, USBSTS 0x401, Reinit
PM: suspend exit
Thunderbolt was reloaded after that successful cycle, then unloaded
again before another suspend attempt. That attempt failed and the system
unexpectedly rebooted.
3. Thunderbolt driver unloaded, using s2idle:
echo none | sudo tee /sys/power/pm_test
echo s2idle | sudo tee /sys/power/mem_sleep
sudo modprobe -r thunderbolt
sudo systemctl suspend
The first cycle successfully resumed:
Oct 07 19:45:29: ACPI: bus type thunderbolt unregistered
Oct 07 19:46:06: PM: suspend entry (s2idle)
Oct 07 19:46:50: usb 1-10: reset low-speed USB device number 5 using xhci_hcd
Oct 07 19:46:50: PM: suspend exit
The Alpine Ridge USB controller remained present and bound to xhci_hcd
afterward.
Without reloading Thunderbolt or rebooting, I ran:
sudo systemctl suspend
On this second cycle, the mouse LED turned off and later turned on
again. After I pressed a key, the system unexpectedly rebooted.
The failed cycle's saved journal ends at:
Oct 07 19:49:11: systemd-sleep: Performing sleep operation 'suspend'...
There is no saved resume sequence, kernel panic, or orderly reboot
sequence for that failure.
Crash-record checks after reboot:
- /sys/fs/pstore was empty.
- /var/lib/systemd/pstore was empty.
- systemd-pstore.service was skipped because /sys/fs/pstore was empty.
The earlier Thunderbolt/xHCI errors may be relevant, but the cause of
the unexpected resets is not established. Unloading Thunderbolt and
selecting s2idle did not provide a reliable workaround.
I have stopped further suspend tests because of the unexpected resets.
Diagnostic information collected by ubuntu-bug accompanies this report.
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: linux-image-7.0.0-38-generic 7.0.0-38.38
ProcVersionSignature: Ubuntu 7.0.0-38.38-generic 7.0.14
Uname: Linux 7.0.0-38-generic x86_64
ApportVersion: 2.34.1-0ubuntu0.1
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: markusulink 1440 F.... wireplumber
/dev/snd/controlC1: markusulink 1440 F.... wireplumber
/dev/snd/seq: markusulink 1414 F.... pipewire
CasperMD5CheckResult: unknown
CurrentDesktop: KDE
Date: Wed Oct 7 19:55:39 2026
MachineType: Apple Inc. iMac18,2
ProcFB: 0 amdgpudrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-7.0.0-38-generic
root=UUID=b2a73e82-ce5c-4b21-9ac1-f5ea9294c807 ro quiet splash
PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No
PulseAudio daemon running, or not running as session daemon.
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 06/23/2024
dmi.bios.release: 0.1
dmi.bios.vendor: Apple Inc.
dmi.bios.version: 529.140.2.0.0
dmi.board.name: Mac-77F17D7DA9285301
dmi.board.vendor: Apple Inc.
dmi.board.version: iMac18,2
dmi.chassis.type: 9
dmi.chassis.vendor: Apple Inc.
dmi.chassis.version: Mac-77F17D7DA9285301
dmi.modalias:
dmi:bvnAppleInc.:bvr529.140.2.0.0:bd06/23/2024:br0.1:svnAppleInc.:pniMac18,2:pvr1.0:rvnAppleInc.:rnMac-77F17D7DA9285301:rvriMac18,2:cvnAppleInc.:ct9:cvrMac-77F17D7DA9285301:sku:pfaiMac:
dmi.product.family: iMac
dmi.product.name: iMac18,2
dmi.product.version: 1.0
dmi.sys.vendor: Apple Inc.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute wayland-session
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https://bugs.launchpad.net/bugs/2169882
Title:
iMac18,2: suspend/wake failure and unexpected reset on second cycle
with Thunderbolt unloaded
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