kern/38556: pkgbuild with nullfs frequently locks up on MP systems

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>Number:         38556
>Category:       kern
>Synopsis:       pkgbuild with nullfs frequently locks up on MP systems
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu May 01 12:30:00 +0000 2008
>Originator:     Andrew Doran
>Release:        NetBSD 4.99.62
>Organization:
The NetBSD Project
>Environment:
n/a
>Description:
The pkgbuild system frequently locks up on MP systems when making
extensive use of null mounts. It appears that vnode locks are being
leaked somewhere. Leaked vnode locks appear to have been taken by
vn_open(), however tracing all the code paths involved show no way
that vnode locks could be leaked there. It may be something more
evil.
>How-To-Repeat:
Run a large pkgbuild system, watch it soft lock-up, try to debug.
>Fix:
Not known.