Hi,
In linux-2.4 kernels, I notice an empty Scsi_Device structure being
added at the end of Scsi_Host list while detecting the scsi devices
[scan_scsis( ) in scsi_scan.c].  This empty structure would get filled
later in scan_scsis_single( ), in which case, again an empty device is
appended.

This being the case, there is a race condition being noticed. Taking a
scenario, if we are adding a scsi driver as a module and at the same
time if we are running a script trying to write to a device (for this
controller), insmod results in seg faults (oops) while accessing invalid
fields of this structure.  The script trying to remove the scsi device
(on the same controller) is attached below (script.txt).  I have
attached the oops message for reference (this is on my RH7.3,  2.4.18-3
kernel):  oops.txt.

The patch for the same is to increment  'access_count' during scanning
of devices.  This patch for 2.4.18 vanilla kernel  is attached below
(2418v.patch)

There is also a race condition when we are trying to read
'/proc/scsi/scsi' continuously in a script and at the same time adding
the module for the controller.   Invalid fields are noticed till the
scanning is complete.  The attached file (proc_read.txt) shows it.  But,
the same logic of incrementing 'access_count' doesn't work here (as you
know) since this field is also
related to mounting of the devices.  This problem looks to be a
limitation.

Please let me know your comments.