devfs and hot unplugging firewire device
M. L. Dodson
mldodson at houston.rr.com
Wed Sep 20 12:14:57 PDT 2006
More experimental results on firewire disks and hot unplugging:
Transcripts of two sessions can be retrieved from
To summarize, on two different machines (histidine and serine)
using two different brands of firewire PCI cards, but both using
Texas Instruments chips, plugging and unplugging an external
firewire device (Ultra ATA Seagate Barracuda 7200.7, 120GB disks
in a combo USB 2.0/Firewire device) in no case gave funky
/dev/da0s1a? devices, if the devices were never mounted (see
earlier postings in this thread). In addition plugging and
unplugging never destroyed the /dev/da0s1a - /dev/da0s1g nodes
created the first time the device was plugged in. The nodes
always persisted for at least 10 minutes past the hot unplug time.
This may be the expected behaviour, but I had thought that the
nodes in /dev for unplugged devices were deleted after some
timeout. I guess I was wrong.
However, after a lot of plugging/unplugging actions (see the
serine transcript), an attempt to mount one of the partitions
caused the machine to become mostly unresponsive: It responded to
the keyboard with the echo, but the contents of the input buffer
did not seem to get further. Attempts to ssh into the machine
were unsuccessful (unresponsive). Attempts to log on as root at
the physical console did not succeed (it went into catatonia after
typing the password and pressing return).
So something is not right with devfs and at least these firewire
cards and device, with multiple hot plug/unplug events.
My hypothesis is that the /dev/da0s1a? devices only appear if you
hot unplug one disk, then immediately plug in another disk (in the
same combo ATA->firewire adapter?). Mounting a partition may also
be necessary for their subsequent creation. Multiple
plugging/unplugging events cause the lockups when a subsequent
attempt to mount one of the partitions is tried.
Any ideas to clue me in? Who should I talk to about firewire
drivers and devfs on -STABLE/-RELEASE?
M. L. Dodson
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