kern/77289: system hangs while trying to unmount previously removed media

Björn König bkoenig at
Tue Feb 8 18:40:24 PST 2005

>Number:         77289
>Category:       kern
>Synopsis:       system hangs while trying to unmount previously removed media
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Feb 09 02:40:22 GMT 2005
>Originator:     Björn König
>Release:        FreeBSD 5.3-RELEASE-p4 i386
System: FreeBSD hoppel.local 5.3-RELEASE-p4 FreeBSD 5.3-RELEASE-p4 #0: Mon Jan 10 10:02:44 CET 2005 root at hoppel.local:/usr/obj/usr/branch/RELENG_5_3/src/sys/HOPPEL i386

	The system hangs while trying to unmount a filesystem of a removable media
	which was already physically removed and also if it was inserted again before.
	This concerns floppy disks. I also noticed similar odd behaviour with usb
	pen drives, but the system reboots instead and there is lot of console output.

	mount a floppy disk

		% mount /dev/fd0 /mnt

	remove media now and unmount the file system
		% umount /mnt
	the following message appears on console:
		fsync: giving up on dirty: 0xc1ec5420: tag devfs, type VCHR,
		usecount 4, writecount 0, refcount 4, flags (VV_OBJBUF),
		lock type devfs: EXCL (count 1) by thread 0xc19adaf0 (pid 590)
		dev fd0

	and mount shows that the filesystem is still mounted. trying to unmount
	it twice let the system stop working immediately.

	a similar case occurs if you mount a floppy disk, remove media, insert
	disk again and then unmount the file system:
		umount: unmount of /mnt failed: Device not configured

	try to unmount it twice - system hangs.


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