I am trying to augment the 2.4.18 SCSI/USB code (usb-storage) code
to be able to hot-plug and detect usb-memory cards when
plugged in. I have things working, except when I pull
out a card when a lot of I/O is happening.
The general strategy that I am using is:
1. a task polls (READ_CAPACITY) for the 3 LUNs that i have
(using a Phison chip).
2. When it succeeds, it mounts the device
-- user process does file i/o --
3. When the card is pulled, ideally, a READ_CAPACITY fails
and the processes with open files are sent a kill signal (SIGHUP)
and the device unmounted.
PROBLEM
When a process is reading from the card, if the card is pulled
the Phison chip sometimes locks up, so I:
1. reset the hub port
2. Fail the pending read
However there is times when the usb (submit) does not come back
fast enough, so the READ_10 times out (seems to take over 10 seconds).
The abort handler is called (by scsi), which unlinks the urb
and says ok (to abort). I then return a DID_ERROR to the
SCSI-CMD. However the bottom half handler of this command
says that since the timer went off, it returns doing nothing.
In the meanwhile the user-process is stuck inside the file/io
routines (waiting on the buffer completion - in TASK_UNINTERRUPTIBLE
state). So I cannot unmount the device (or handle new mounts).
Questions:
1. Is there a better strategy than the above for dectecting
plug-unplug?
2. How do i handle the failure?
3. What am i supposed to do in abort handler, so that the SCSI
subsystem can continue working?
Thanks,
Dave
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