Raspberry PI Compute Module 5 - eMMC write hungs in kernel during tar.gz unpack

[berndbenner]

Describe the bug

We have made a base board for a DIN Mounting Rail, with a Raspberry PI Compute Module 5 for data acquisition and control.
Now I am trying to run our python installation tool on the CM5 to setup the eMMC-partitions, filesystems and config files.
The tool is able to setup partitions and popule filesystems on PCIe-NVME, USB-Sticks and mmc/sd-cards by calling system tools like fdisk,parted, tar, pigz, df etc.

The tool is able to setup all other testet media [ NVME, slow and fast USB-sticks ] , but not the CM5 eMMC- flash.

What happens:

The tool will setup the partitions, format the target mmc-rootfs-partition with ext4 and extract a tar.gz ( with pigz ) over a pipe very fast from a tar container file ( loaded from the usb-boot device ) to the mountpoint-dir of the emmc-rootfs.

The error appears during extraction of a tar.gz with uncompressed/compressed size of 4.4 GB/1.8 GB to the rootfs partition mmcblk0p5.

I try to slow down the extraction, by using gzip instead of pigz-extraction, but this will affect only the frequency of hung/deadlock errors.

Our python tool will extract the gz-archive in a background thread calling os.system('tar ...').
A foreground thread will call os.system('df -lBk /mnt/mountpoint') every 0.5 s to get the progress information from the used-col of the df-output.

partition layout of the eMMC-device

The tool partitions the eMMC with 1 GB boot and 2 logical drives of 20 and 37 GB size.

root@rta-sl-mhinst-000:/projects# fdisk -l /dev/mmcblk0
Disk /dev/mmcblk0: 58.24 GiB, 62537072640 bytes, 122142720 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x6aaa2ac9
/dev/mmcblk0p1 *           8   2097167   2097160    1G  c W95 FAT32 (LBA)
/dev/mmcblk0p2       2097176 122142719 120045544 57.2G  f W95 Ext'd (LBA)
/dev/mmcblk0p5       2097184  44040231  41943048   20G 83 Linux
/dev/mmcblk0p6      44040240 122142719  78102480 37.2G 83 Linux

The error appears in 90 % of the starts of the tool. After hung of the tar-gz extraction I need to reboot, because the background tar-process will hung in a kernel function and I am unable to kill it. The access to the eMMC is blocked.

root@rta-sl-mhinst-000:/projects/rtflex# ps aux | grep tar
root        1085  0.0  0.0  11520  7760 ?        Ss   13:09   0:00 sshd: /usr/sbin/sshd -D [listener] 0 of 10-100 startups
root        7516  0.0  0.0   9024  4128 pts/0    D    13:27   0:01 tar -C /mnt/itarget -xzf -
root        7517  0.0  0.0      0     0 pts/0    Z    13:27   0:00 [tar] <defunct>
root       40460  0.0  0.0   6384  2128 pts/1    S+   14:27   0:00 grep tar

Our tool will execute 'echo 0 > /proc/sys/kernel/hung_task_timeout_secs' to avoid kernel hung messages of background ext4-journal sync processes.

If I do not switch off hung_task_timeout, I get the hung messages in the kernel log, but this will also happen on installations to slow usb-devices, but without a complete hung of the device.

With 'echo 0 > /proc/sys/kernel/hung_task_timeout_secs' there are no kernel error message.
The last message is the mount of the filesystem

root@rta-sl-mhinst-000:/projects/rtflex#journalctl -k -f
Feb 17 14:52:07 rta-sl-mhinst-000 kernel: EXT4-fs (mmcblk0p5): mounted filesystem 

I am using the newest kernel 6.12.62+rpt-rpi-2712
and a CM5 with 16GB RAM and 64 GB eMMC Flash.

Revision        : e04180
Serial          : 785aeb8744d30d55
Model           : Raspberry Pi Compute Module 5 Rev 1.0

Steps to reproduce the behaviour

The error can be reproduced on a similar prepared eMMC and a similar sized tar.gz archive with 2 terminals

first terminal:

mount /dev/mmcblk0p5 /mnt/mmcblk0p5
tar -C /mnt/mmcblk0p5 -xf setup-root.tar.gz --use-compress-program=pigz

second terminal:

watch df -lBk /dev/mmcblk0p5

Device (s)

Raspberry Pi CM5

System

Raspberry Pi reference 2025-12-04
Generated using pi-gen, https://github.com/RPi-Distro/pi-gen, 4997bf4e4e49bc3305eb182a4a08bd023529da04, stage4
root@rta-sl-mhinst-000:/projects/rtflex#

2025/12/08 19:29:54
Copyright (c) 2012 Broadcom
version 2226a853 (release) (embedded)

Logs

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Additional context

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