Re: CVS commit: src/sys

[Michael van Elst <mlelstv%serpens.de@localhost>]

On Sun, Apr 28, 2013 at 10:31:19AM +0200, J. Hannken-Illjes wrote:
> On Apr 27, 2013, at 12:27 AM, Michael van Elst <mlelstv%netbsd.org@localhost> 
> wrote:
> 
> > Module Name:        src
> > Committed By:       mlelstv
> > Date:               Fri Apr 26 22:27:17 UTC 2013
> > 
> > Modified Files:
> >     src/sys/kern: vfs_mount.c
> >     src/sys/sys: mount.h
> > 
> > Log Message:
> > Correct umount semantics to return EBUSY when a filesystem is busy
> > instead of failing filesystem operations with EBUSY when attempting
> > an umount.
> > This fixes kern/38141.
> 
> Who did the review or where has it been discussed?

Christos with a former version and David Holland with the current.

> We now get a deadlock between mountlist_lock and mnt_unmounting,
> seen between dounmount() and do_sys_sync() for example.

Do you have a PR showing how to produce that deadlock?

> The lock order is mountlist_lock->mnt_unmounting, but dounmount()
> locks in reverse direction.

The locking order hasn't been changed, but the faulty tryenter has been
replaced with an enter. If there is a locking violation it just didn't
show up with the former code as even LOCKDEBUG had been hacked to allow
it.



Greetings,
-- 
                                Michael van Elst
Internet: mlelstv%serpens.de@localhost
                                "A potential Snark may lurk in every tree."