drivers.
The bug occurrs when a userland process has the driver instance
open and the underlying device goes away. We get the devfs
callback that the device node has been destroyed, but not all of
the closes necessary to fully decrement the reference count on the
CAM peripheral.
The reason is that once devfs calls back and says the device has
been destroyed, it is moved off to deadfs, and devfs guarantees
that there will be no more open or close calls. So the solution
is to keep track of how many outstanding open calls there are on
the device, and just release that many references when we get the
callback from devfs.
scsi_pass.c,
scsi_enc.c,
scsi_enc_internal.h: Add an open count to the softc in these
drivers. Increment it on open and
decrement it on close.
When we get a devfs callback to say that
the device node has gone away, decrement
the peripheral reference count by the
number of still outstanding opens.
Make sure we don't access the peripheral
with cam_periph_unlock() after what might
be the final call to
cam_periph_release_locked(). The
peripheral might have been freed, and we
will be dereferencing freed memory.
scsi_ch.c,
scsi_sg.c: For the ch(4) and sg(4) drivers, add the
same changes described above, and in
addition, fix another bug that was
previously fixed in the pass(4) and enc(4)
drivers.
These drivers were calling destroy_dev()
from their cleanup routine, but that could
cause a deadlock because the cleanup
routine could be indirectly called from
the driver's close routine. This would
cause a deadlock, because the device node
is being held open by the active close
call, and can't be destroyed.
Sponsored by: Spectra Logic Corporation
MFC after: 1 week
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