[systemd-devel] udev and probing of eMMC partition devices

[Lennart Poettering]

On Mo, 21.09.20 19:03, Alan Perry (alanp at snowmoose.com) wrote:

>
> Hi,
>
> I am trying to understand behavior that I am seeing with udev and eMMC
> partition devices and was hoping that someone here could help.
>
> The system that I am running has an eMMC device with something like 7-8
> partitions. The kernel does add block events for the device and each of it
> partitions and the logs show them being queued up by udevd. Then things get
> interesting. Sometimes processing of the add event for the device itself
> gets to a probe step and, in the time frame of the logs that I have, never
> gets further in that processing and the add block device events for the
> partitions are never processed. However, usually, it will process the add
> block device event for the entire device and after that (as per the
> implementation of is_devpath_busy()) start processing the add block events
> for the partition devices. Often times, the processing of the partition
> device add events will get stuck at the probe step.

"Get stuck"? What does that mean? What is it actually doing? What does
a stack trace say? Anything in the logs?

> The partition devices
> stuck at the probe are then "waiting" and the services that depend on them
> blocked.
>
> Can anyone here give me some insight into what is going on, in particular,
> how there is such difference in behavior between test runs on the same
> system?

Have you checked the logs?

Please always start with saying which systemd version this is, and
which distro, otherwise it's very hard to grok what your setup is
like?

Maybe the eMMC driver has issues and simply hangs? dmesg might show
something in that case.

Lennart

--
Lennart Poettering, Berlin