RFR: 8253435: Cgroup: 'stomping of _mount_path' crash if manually mounted cpusets exist [v2]

[Severin Gehwolf]

On Fri, 25 Sep 2020 14:24:22 GMT, Bob Vandette <bobv at openjdk.org> wrote:

> In my suggestion, it doesn't matter which entry is first. If we see the manual on first, record it. When the second one
> comes around, replace the first one if it's /sys/fs/cgroup. In the very unlikely event that there isn't a second
> non-manual one, I think we still want to record the manaul mount point since there could be a cpuset limit setup which
> we should respect.  As for the second point about /sys/fs/cgroup, I think that using this string is just as good if not
> better than assuming they are all mounted in the same subdirectory.  If you follow my suggestion, then we will only be
> subjected to a failure to mount if there are two cpuset mount entries AND neither are mounted on /sys/fs/cgroup/cpuset.

Like this perhaps?
https://github.com/jerboaa/jdk/commit/45608cf9a13068f3724cc65d12d8dc819bb2d066

I tend to think that in actual container workloads it might be unlikely to actually see multiple cpuset mounts. So in a
sense that's a special case. The general case, before this bug, shouldn't be penalized. So perhaps the above would be
worth considering.

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PR: https://git.openjdk.java.net/jdk/pull/295