> > how can vn_lock(LK_EXCLUSIVE | LK_RETRY) fail in this case?
> 
> Somehow the lock is dying.

dying?  can you please be more specific?

> Yes, for it to happen we have to have
> wandered into the weeds, but this code methodology is to try and help us 
> get somewhere a bit safer. i.e. not add more error states on top if we 
> don't have to.

we have many code which assume that vn_lock with LK_RETRY never fails.
are you going to add error checks on all of them?
i think that it just bloats the code without any benefits.

YAMAMOTO Takashi