kern/145750: unionfs locks the machine

[Harald Schmalzbauer]

>Number:         145750
>Category:       kern
>Synopsis:       unionfs locks the machine
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Apr 16 07:20:00 UTC 2010
>Closed-Date:
>Last-Modified:
>Originator:     Harald Schmalzbauer
>Release:        FreeBSD 8.0-RELEASE-p2 amd64
>Organization:
>Environment:
System: FreeBSD devweb.dmz.sand.spsnetz.de 8.0-RELEASE-p2 FreeBSD 8.0-RELEASE-p2 #2: Fri Feb 5 15:06:19 CET 2010 admin at devweb.dmz.sand.spsnetz.de:/usr/obj/usr/src/sys/DELL-PE840 amd64


	
>Description:
	There are several LORs with unionfs reported. One seems to lead to a hard lock.
For example I used to mount /usr/local/etc via unionfs over read-only unerlaying ufs.
There are reproducably hanging processes with status D+ ofter a short time.
This used to work with FreeBSD-7, but also causes problems on -current (see kern/141950)
>How-To-Repeat:
	mount_unionfs /somedir/anotherdir /usr/local/etc and try starting lighttpd
with php-fastcgi for example.
mount_unionfs /somedir /root while / is readonly. Su will hang and force yout to hard reset the machine.
>Fix:

	


>Release-Note:
>Audit-Trail:
>Unformatted: