[solved] systemd 230 automount: hangups with kernels <4.6.2

[crashmaster]

With release 230 of systemd i've got problems with automount (local and remote filesystems).
The first mount works always fine, but a later mount (after an internal umount) lets processes wait forever (hangup)
First you think it's a bug in systemd but it is a kernel bug (lock/unlock problem). The responsible function for this has been completely rewritten and it seems that this code is in the kernel since some versions ago.

The situation is:
- using a kernel which is old enough (i tested it with 4.0.x on Intel Edison) automount in systemd 230 works fine
- using systemd <230 and it works fine with all kernel versions

With systemd 230 i have the problem on Raspberry (4.4.13 kernel) and Cubieboard (4.6.1 kernel).
Kernel 4.6.2 was just released and it solves this problem. Everything works fine again (in the x86 world of Arch).

It seems like systemd 230 uses some new features of the rewritten kernel function so the bug may happen only in this combination.

My question is: Will there be any patches for the older 4.4. kernels on RPi or do we have to wait for a kernel >= 4.6.2 ?

Thanks, CM.

P.S. I don't want to use 229 so far because it has a "OnCalendar=" scheduling problem using timer units.

[WarheadsSE]

Please check the system journal/coredumps for syscall errors.

[crashmaster]

There is no really helpful content. It's not a bug which has to be found, it's one which has been found.
see this please: https://github.com/systemd/systemd/issues/3410

P.S.: sorry about my English (not my home language) - maybe and hopefully only sometimes it's probably confusing.

[crashmaster]

To make things a little bit more clear:

If you use systemd automount either in fstab or in a mount unit file AND the "OnCalendar=xx-xx-xx yy:yy:yy" param is used in a timer unit with the current kernel you should use systemd 226 (229 has this "OnCalendar" bug which is fixed in 230).
Hence If you don't use automounts (resp. autofs) you should have fun with the current 4.4 kernel and systemd 230 - you don't have to take care for anything.

Details for the "OnCalendar=" bug, see this: https://github.com/systemd/systemd/issues/2682
It was fixed by the systemd people at the end of February, in Arch we've got the fix with 230 now.

If you run into the automount bug which means a process is hanging (it waits forever for an unlock), it should help to do a "systemctl daemon-reload" from another shell and the hanging process continues immediately. That's what was fixed in kernel 4.6.2 (see changelog at kernel.org) and it is my workaround at the moment.

[crashmaster]

These issues were solved now.

Also systemd automount works again perfectly after installing the updates coming in the last days.
It also works fine on RPi 1 with kernel 4.4.14 (i guess it has got the necessary patches).

Many thanks !