Lennart Poettering
1483892a42
Notifications from /proc/self/mountinfo are async, so if we stop a service (and while doing so get rid of the credentials mount point of it), then it will take a while until the notification reaches us and we actually scan the table again. In particular as we nowadays ratelimit notifications on the table, since it's so inefficient. And as I learnt the ratelimiting is actually quite regularly hit during shutdown, where a flurry of umount events are genreated. Hence, let's check if a mount point is actually a mountpoint before trying to unmount it. And if it isn't let's wait for the notification to come in. (This race might be triggred not just by us on ourselves btw: there are other daemons that unmount stuff when stopping where the race also exists, but might simply be harder to trigger: if during service shutdown these services remove some mount then they might collide with us doing the same. After all, we have the rule to unmount everything mounted automatically for you during shutdown.) In the long run we should also start making us of this when it becomes available: https://github.com/util-linux/util-linux/issues/2132 With that we can make issues like this go away entirely from our side of things at least. Fixes: #25527
System and Service Manager
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