Created attachment 287833 [details] Dmesg when disconnecting power, rebooting and freeze. Hello, I have a Lenovo C940 with Manjaro, tested with kernels 5.4, 5.5 and 5.6-rc4. If I reboot/shutdown the laptop after connecting/disconnecting the usb-c charger it "may" leads to system freeze during reboot after OS shutdown. This is not a systematic bug, when it happens, the OS cleanly shutdown, the screen becomes black but with backlight still on and freeze. Sysreq keys do not work at this stage. Nothing else is connected to the laptop. I need to force shutdown by keeping the power button pushed for a few seconds. When powering on back the laptop, if I do not plug/unplug anything on the usb-c power port, bug will most probably occur again at the next reboot. The only systematic way to be able to keep the laptop rebooting correctly is to plug back the power usb-c when the laptop is off. I joined the dmesg/system journal logs after a first clean boot, with power disconnection and then a reboot with freeze. Under Windows all seems to work fine. Also, this is not happening 100% of the time. I may have several successful reboots while having connected/disconnected usb-c. Most of the time, only repeating a connection/disconnection is enough to get the bug. I tried also with a usb-c dock and same bug appeared. Not sure how to get more logs from kernel after journal daemon is turned off by the OS. I welcome any suggestions to narrow down this bug. Thanks for the help.
Created attachment 287835 [details] Journalctl when disconnecting power usb-c, rebooting and freeze.
we know that it could causes an interrupts storm. please try 1. grep . /sys/firmware/acpi/interrupts > interrupt-before-1; sleep 10; grep . /sys/firmware/acpi/interrupts > interrupt-after-1 2. connect/disconnect the USB-C Charger 3. grep . /sys/firmware/acpi/interrupts > interrupt-before-2; sleep 10; grep . /sys/firmware/acpi/interrupts > interrupt-after-2 it is probably an interrupt storm has occurred and it freezes the reboot process.
Created attachment 290303 [details] Interrupts counters cd /sys/firmware/acpi/interrupts/ grep . * > /tmp/interrupt-before-1; sleep 10; grep . * > /tmp/interrupt-after-1 grep . * > /tmp/interrupt-before-2; sleep 10; grep . * > /tmp/interrupt-after-2
(In reply to Zhang Rui from comment #2) > we know that it could causes an interrupts storm. > please try > 1. grep . /sys/firmware/acpi/interrupts > interrupt-before-1; sleep 10; grep > . /sys/firmware/acpi/interrupts > interrupt-after-1 > 2. connect/disconnect the USB-C Charger > 3. grep . /sys/firmware/acpi/interrupts > interrupt-before-2; sleep 10; grep > . /sys/firmware/acpi/interrupts > interrupt-after-2 > > it is probably an interrupt storm has occurred and it freezes the reboot > process. Thanks for your feedback, I joined the results for your command. It has been executed under Fedora 32 with Kernel 5.7.8-200.fc32.x86_64.
Finally I was able to avoid the freeze by adding intel_iommu=off to Grub. Disabling the VT-d option in the Bios works too. This seems related to: https://bugzilla.kernel.org/show_bug.cgi?id=206571