Kernel Dump when accessing second drive

[YONETANI Tomokazu]

On Sun, May 09, 2010 at 12:15:55AM -0700, Dylan Reinhold wrote:
> I added a second drive, to copy ~100GB's to my machine, but the
> kernel panics when I try and rsync the data.
> The second drive is formated ext2 and mounted as readonly.
			:
> Unread portion of the kernel message buffer:
> ad6: FAILURE - device detached
> subdisk6: detached
> ad6: detached
			:
> #16 0xc032f0ac in devstat_end_transaction_buf (ds=0x18,
> bp=0xc1f6f5d0) at /usr/src/sys/kern/subr_devstat.c:248
> #17 0xc01bb669 in ad_done (request=0xc1d6f7e8) at
> /usr/src/sys/dev/disk/nata/ata-disk.c:368

   358  ad_done(struct ata_request *request)
   359  {
   360      struct ad_softc *adp = device_get_ivars(request->dev);
   361      struct bio *bp = request->bio;
   362      struct buf *bbp = bp->bio_buf;
   363
   364      /* finish up transfer */
   365      if ((bbp->b_error = request->result))
   366          bbp->b_flags |= B_ERROR;
   367      bbp->b_resid = bbp->b_bcount - request->donecount;
*  368      devstat_end_transaction_buf(&adp->stats, bbp);

I'm under the impression that the machine was panicked because
the interrupt was delivered after ad6 was detached for some reason.
ad_detach() in fact sets NULL to the device's ivars.

So probably you need to look into the log and find out why it was
detached in the first place.