Bug 5237

Created attachment 5983 [details]
info.050913.bz2

It seems that even the perl sample code is translated into python. The write()
can still finish with "Segmentation fault". The thread must be used so the
write() will hang and cause scsi_eh_XX to hang also. The code is as below:

=====================================================================
#!/usr/bin/python

import os
import sys
import time
import thread

n = int(sys.argv[1])

deviceDir = '/sys/devices/pci0000:00/0000:00:1d.7/usb5/5-1/5-1:1.0/'
rescanFile = deviceDir + 'host%d/target%d:0:0/%d:0:0:0/rescan' % ((n,) * 3)
sizeFile = deviceDir + 'host%d/target%d:0:0/%d:0:0:0/block/size' % ((n,) * 3)

bDone = False

def Run():
	while True:
		if not os.path.isdir(deviceDir):
			print '"%s" is gone!' % deviceDir
			break

		if not os.path.exists(sizeFile):
			print '"%s" is gone!' % sizeFile
			break

		size = file(sizeFile, 'r').read()
		if size == "0\n":
			print "Size becomes 0!"
			break

		print '***open ' + rescanFile
		try:
			fd = os.open(rescanFile, os.O_WRONLY);

			print "write 1 to rescan file";
			os.write(fd, "1")

			print 'try to close'
			os.close(fd)
			print 'close done'
		except (IOError, OSError):
			break

		time.sleep(0.1);	# 0.1 second

if __name__ == "__main__":

	thread.start_new_thread(Run, ())

	while not bDone:
		time.sleep(0.2)

	print 'Finish!!!!!!'

=====================================================================

I don't understand, is the kernel oopsing when you do this?

If so, please provide the oops message.

Greg, sorry I don't understand what you mean (My English is bad...) and reply
this so lately since I seemed not got notified. What I want is that the storage
driver can just remove the /sys files for that device when I try to do rescan
without hanging the write() function call.

When the card reader is removed while the rescan operation (write() function
call) is continuously tried, the usb_storage driver will disappear as expected.
The corresponding sys files in /sys/class/usb_device/, /sys/class/scsi_host/,
/sys/class/scsi_device/,  and /sys/class/usb_device/ will also disappear.
Howerver, the scsi_eh_X driver won't get released and my write() is pended
forever even after my program is terminated by CTRL-C.

Now I try linux-2.6.14-rc4 with squashfs and unionfs patches. The error
condition still happens. I tried several times to produce the error and the ps
result is different from what I previously reported:

~ 1000$ ps -eo pid,tid,class,rtprio,ni,pri,psr,pcpu,stat,wchan:30,comm | grep usb
~ 1001$ ps -eo pid,tid,class,rtprio,ni,pri,psr,pcpu,stat,wchan:30,comm | grep scsi
 3838  3838 TS       -  -5  28   0  0.0 S<   scsi_error_handler            
scsi_eh_0
~ 1002$ 

By the way, I wrongly filled the "Most recent kernel where this bug did not
occur:" field. It should be "2.6.11" instead of "2.6.13-mm1"

The usb storage verbose message "info.051011.bz2" is as attached.

Created attachment 6275 [details]
/var/log/kernel/info

Hi,
This time I enabled the SCS log function to log all SCSI messages. Two logs are
attached. The first one (info.expected) is for the non-thread version. The
rescan operation will fail and my program will terminate as expected. The second
one (info.hang) is for the threaded version and the write() hangs. After I
CTRL-C the program after some delay, the log is still the same (no more messages
appended). I also attached my simple python program (use the variable bUseThread
to enable/disable thread). The kernel symbol file is also attached. It seems the
problem is in the SCSI module....

Created attachment 6339 [details]
info.expected

Created attachment 6340 [details]
info.hang

Created attachment 6341 [details]
rescan.py

Created attachment 6342 [details]
kallsyms

Can you try this again using 2.6.14?

Created attachment 6431 [details]
info.051101.bz2

Hi,
    The result is the same for 2.6.14 (with unionfs and squashfs patches). I
also update the kernel log and kallsyms here.

[root@fsyang fsyang]# ps -eo
pid,tid,class,rtprio,ni,pri,psr,pcpu,stat,wchan:30,comm | grep usb
[root@fsyang fsyang]# ps -eo
pid,tid,class,rtprio,ni,pri,psr,pcpu,stat,wchan:30,comm | grep scsi
 4913  4913 TS	     -	-5  28	 0  0.0 S<   scsi_error_handler 	   
scsi_eh_3

By the way, could any body tell me why I am not notified when this bug is
modified? I had ever received some notifications before. But now I am not
notified so that I must check this bug daily... Thanks...

Created attachment 6432 [details]
kallsyms.051101.bz2

I am able to reproduce the failure on my computer, and I'm working to fix it.

You should be receiving email notifications about updates to this bug.  Bugzilla
does send out a message automatically to the address listed as the Submitter.

Created attachment 6452 [details]
Fix race between sd_rescan and sd_remove

Try the attached patch.  It fixed the problem on my computer.

Hi,
    I have tried your patch and things worked as expected so far. Thanks a lot.