Re: Another force unmount failure

[David Holland <dholland-tech%netbsd.org@localhost>]

On Thu, Jul 16, 2015 at 07:34:20PM +0200, Emmanuel Dreyfus wrote:
 > David Holland <dholland-tech%netbsd.org@localhost> wrote:
 > 
 > > Either make vnode locks interruptible, or debug puffs.
 > > 
 > > I favor the former, but lost the argument a few years back. Others
 > > (including e.g. yamt) said no.
 > 
 > Even as not interruptible, I can call VOP_LOCK with LK_NOWAIT and loop
 > on it until I decide it is time to give up.

Busy-looping like that on a vnode lock is Wrong(TM).

 > But once I failed to acquire
 > filesystem root vnode lock, how can I forcibly unmount it?

You probably can't. It would be nice to have recovery logic for that
level of problem, but it's not likely to happen anytime soon.

-- 
David A. Holland
dholland%netbsd.org@localhost