This weekend I was hacking around with a trivial USB driver for talking
to the boot load firmware of a USB Bit Whacker. It's running the
MicroChip Pic18 boot loader firmware and I'm putting together a flash
program for writing new FW to the thing.
Anyway in my use of the usb-skeleton.c as my starting point I discovered
my test program was getting hung up after attempting to write a buffer.
The application and driver where hung in a way that required me to
reboot to get it to clean up so I could try again.
It turned out the code path through skel_open can grap the driver's
io_mutex lock and forget to release it.
The following patch fixes the problem for me.
--mgross
Signed-off-by: Mark Gross <mgross@linux.intel.com>
diff -urN -X linux-2.6.23-rc7/Documentation/dontdiff linux-2.6.23-rc7/drivers/usb/usb-skeleton.c linux-2.6.23-rc7-bugfix/drivers/usb/usb-skeleton.c
--- linux-2.6.23-rc7/drivers/usb/usb-skeleton.c 2007-09-24 08:57:54.000000000 -0700
+++ linux-2.6.23-rc7-bugfix/drivers/usb/usb-skeleton.c 2007-09-24 09:01:43.000000000 -0700
@@ -125,6 +125,7 @@
/* save our object in the file's private structure */
file->private_data = dev;
+ mutex_unlock(&dev->io_mutex);
exit:
return retval;
-
