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Date:      Mon, 23 Apr 2001 15:10:07 -0700 (PDT)
From:      John Baldwin <jhb@FreeBSD.org>
To:        Jens Schweikhardt <schweikh@schweikhardt.net>
Cc:        freebsd-current@FreeBSD.org
Subject:   RE: duplicate locks and lock order reversal
Message-ID:  <XFMail.010423151007.jhb@FreeBSD.org>
In-Reply-To: <20010423225230.A974@schweikhardt.net>

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On 23-Apr-01 Jens Schweikhardt wrote:
> hello, world\n
> 
> my current kernel cvsupped around Apr 14th tells me about
> duplicate locks and lock order reversal. Is this reason to worry?
> ...
> Apr 23 22:23:09 hal9000 /boot/kernel/kernel: da0 at ahc0 bus 0 target 2 lun 0
> Apr 23 22:23:10 hal9000 /boot/kernel/kernel: da0: <IBM DCAS-34330 S65A> Fixed
> Direct Access SCSI-2 device 
> Apr 23 22:23:10 hal9000 /boot/kernel/kernel: da0: 20.000MB/s transfers
> (20.000MHz, offset 15)
> Apr 23 22:23:10 hal9000 /boot/kernel/kernel: da0: 4134MB (8467200 512 byte
> sectors: 255H 63S/T 527C)
> Apr 23 22:23:10 hal9000 /boot/kernel/kernel: acquring duplicate lock of same
> type: "allproc"
> Apr 23 22:23:10 hal9000 /boot/kernel/kernel: 1st @
> /usr/src/sys/kern/kern_proc.c:584
> Apr 23 22:23:10 hal9000 /boot/kernel/kernel: 2nd @
> /usr/src/sys/kern/kern_proc.c:143
> Apr 23 22:23:10 hal9000 /boot/kernel/kernel: lock order reversal
> Apr 23 22:23:10 hal9000 /boot/kernel/kernel: 1st vnode interlock last
> acquired @ /usr/src/sys/kern/vfs_vnops.c:625
> Apr 23 22:23:10 hal9000 /boot/kernel/kernel: 2nd 0xc03c0120 mntvnode @
> /usr/src/sys/ufs/ffs/ffs_vfsops.c:967
> Apr 23 22:23:10 hal9000 /boot/kernel/kernel: 3rd 0xc8f68eac vnode interlock @
> /usr/src/sys/ufs/ffs/ffs_vfsops.c:976
> Apr 23 22:23:10 hal9000 lpd[315]: lpd startup: logging=0
> Apr 23 22:24:08 hal9000 /boot/kernel/kernel: cd0 at ahc0 bus 0 target 3 lun 0
> Apr 23 22:24:08 hal9000 /boot/kernel/kernel: cd0: <YAMAHA CRW6416S 1.0b>
> Removable CD-ROM SCSI-2 device 
> Apr 23 22:24:08 hal9000 /boot/kernel/kernel: cd0: 10.000MB/s transfers
> (10.000MHz, offset 15)
> Apr 23 22:24:08 hal9000 /boot/kernel/kernel: cd0: Attempt to query device
> size failed: NOT READY, Medium not present - tray closed
> Apr 23 22:26:44 hal9000 /boot/kernel/kernel: i4b: unit 0, assigned TEI = 126
> = 0x7e
> Apr 23 22:27:08 hal9000 /boot/kernel/kernel: [agree] 

This is a FAQ.  Please keep up with -current if you are tracking it.  These are
known and not a problem right now.  The VFS reversals have been around for a
long time unfortunately, and the allproc warning is due to witness still
needing some work to better handle recursing on sx locks.

-- 

John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/
PGP Key: http://www.baldwin.cx/~john/pgpkey.asc
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

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