Kernel panic when serial device resets

[benlye]

Describe the bug
I maintain a plugin for the 3D printer host software OctoPrint which is used to update printer firmware. One of the types of printer is updated by resetting the serial device. I have observed that resetting this serial device will periodically cause a kernel panic.

I have reproduced this problem on two different Pi 3 Model B including one which was a clean install of Raspbian, fully updated this morning.

To reproduce
Running this shell script with the printer board plugged in will eventually crash the Pi (typically after 5-15 resets):

stty -F /dev/ttyACM0 115200 -echo > /dev/null
i=0; while true; do echo $i; echo M997 >> /dev/ttyACM0; ((i=i+1)); sleep 15; done

'M997' is the command that triggers the board to reset. It resets almost immediately on receiving the command. My last test took 20 resets before it crashed but it's been as few as 1. I can reproduce the problem at will by running the code above for a few minutes

The board in this case is a BTT SKR v1.4 Turbo, which has an LPC1769 MCU. The board presents its on-board SD card as a USB storage device and a cdc_acm serial port to the host. I've had the same problem with other boards of a similar configuration.

Expected behaviour
A kernel panic should not occur after resetting the serial device

Actual behaviour
The system crashes with a kernel panic.

Kernel panic output captured from the serial console:
https://pastebin.com/zSiAAZCg

System

• raspinfo output
  https://pastebin.com/FyhjskHU

• Which model of Raspberry Pi? e.g. Pi3B+, PiZeroW
  Pi 3 model B

• Which OS and version (cat /etc/rpi-issue)?

pi@raspberrypi:~ $ cat /etc/rpi-issue
Raspberry Pi reference 2021-01-11
Generated using pi-gen, https://github.com/RPi-Distro/pi-gen, 21090519d85bdaa1615d5d5057d37b09368ea5d2, stage2

• Which firmware version (vcgencmd version)?

pi@raspberrypi:~ $ vcgencmd version
Jan 27 2021 22:26:53
Copyright (c) 2012 Broadcom
version 99d9a48302e4553cff3688692bb7e9ac760a03fa (clean) (release) (start)

• Which kernel version (uname -a)?

pi@raspberrypi:~ $ uname -a
Linux raspberrypi 5.10.11-v7+ #1399 SMP Thu Jan 28 12:06:05 GMT 2021 armv7l GNU/Linux

[pelwell]

I don't see any Pi-specific software in that stack trace - have you tried in a different Linux system such as a PC?

[benlye]

I don't see any Pi-specific software in that stack trace - have you tried in a different Linux system such as a PC?

I can set up a PC to try it on. Any suggestions for best (most approximate to Raspbian) distribution to use? Just a vanilla Buster install?

[benlye]

Testing on a Lenovo M93p PC:

• Ubuntu 20.04 - 50 consecutive resets with no panics.
• Debian Buster - 100 consecutive resets with no panics.

On both Pi 3s I have I get a panic after at most 20-25 resets, so I'm fairly sure the problem won't happen on the other hardware.

What can I do/test on the Pi to gather more information?

[benlye]

If building a debug kernel (or anything similar) would be useful, I'm happy to give it a go. I'm willing to do whatever is helpful to dig into this, but I need some pointers.

[benlye]

Another data point - I can also make the crash occur on a Pi 4 Model B using the same script.

[kantlivelong]

Seeing this as well.