Is it possible to unmount resctrl once the system is in this state?No, it can't be unmounted, as there is no mount exist.
root@localhost:~# mount -t resctrl resctrl /test# mount -t resctrl resctrl /sys/fs/resctrl
mount: /sys/fs/resctrl: mount point does not exist.
What if you now try to mount resctrl somewhere else, e.g.:
# mount -t resctrl resctrl /mnt
if "resctrl" is nonfunctional in this state, then this comment[1] here does *not* make sense.
I'm guessing this _should_ fail if you weren't able to unmount resctrl,
since resctrl seems to forbid multiple mount instances.
I'm not sure what the best behaviour is here. Leaving resctrl "half-
mounted" might be a good thing: at this point the system is in a semi-
bad state we want to make sure it can't be remounted. Unregistering the
resctrl filesystem from the fs core feels cleaner if feasible though.
Leaving an impossible unmount operation for init to do during reboot/
shutdown feels unfortunate.
We might have to look at what other filesystems do in this area.
The mount machinery does provide other ways of getting into broken,
impossible situations from userspace, so this doesn't feel like an
entirely new problem.
Additionally, a question regarding this, Is a complete system restart
necessary to regain the mount?
Thanks
-Amit
I think James will need to comment on this, but I think that yes, it
is probably appropriate to require a reboot. I think an MPAM error
interrupt should only happen if the software did something wrong, so
it's a bit like hitting a BUG(): we don't promise that everything works
100% properly until the system is restarted. Misbehaviour should be
contained to MPAM though.