[patch] usb-skeleton leaking locks on open.

From: Mark Gross
Date: Mon Sep 24 2007 - 12:18:53 EST

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.


Signed-off-by: Mark Gross <mgross@xxxxxxxxxxxxxxx>

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);

return retval;
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