Re: kern/45305: umount says device busy without any process having current directory in the mount or file open

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

The following reply was made to PR kern/45305; it has been noted by GNATS.

From: David Holland <dholland-bugs%netbsd.org@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: kern/45305: umount says device busy without any process having
 current directory in the mount or file open
Date: Thu, 29 Sep 2011 00:29:43 +0000

 On Tue, Sep 27, 2011 at 02:10:06PM +0000, Matthias Kretschmer wrote:
  >  Are there any counters of open/etc. files for a mount-point?  Am I able
  >  to output these somehow?  As there is no record of anything accessing
  >  the corresponding mount-points I'm wondering why the systems thinks it
  >  is busy.
 
 The usual cause of this problem is refcount leaks on vnodes, which are
 a royal pain to track down. Figuring out a sequence of actions that
 causes it makes it much easier, as it allows restricting the search to
 a particular code path.
 
 I've been thinking about writing vnode refdebug code (similar in
 concept to LOCKDEBUG) but it's not entirely trivial...
 
 -- 
 David A. Holland
 dholland%netbsd.org@localhost