OSTree locking fails sometimes

[Stefan Agner <stefan agner ch>]

Hello,

We are using meta-updater which makes use of OSTree. Every now and then
we encounter a locking issue in our CI build infrastructure. The issue
has been reported and is largely documented here:
https://github.com/advancedtelematic/meta-updater/issues/412

tl;dr version:

We are using:
ostree commit
and then
ostree summary -u

And get this every now and then:
"error: Locking repo exclusive failed: Resource temporarily unavailable"

While we run multiple builds in parallel which eventually commit into
the same OSTree, we do serialize them using bitbake's lockfiles feature.

The common storage is a NFS mount. OSTree seems to make use of the open
file description locks (according to strace) and seems to behave well.
Ideas what could cause that issue or hints on how to investigate
further?

--
Stefan