USB: fix BUG: sleeping function called from invalid context at...

USB: fix BUG: sleeping function called from invalid context at /home/jeremy/hg/xen/paravirt/linux/drivers/usb/core/urb.c:524, in_atomic():1, irqs_disabled():0

Clearly there's a bug in
drivers/usb/serial/usb-serial.c:usb_serial_put().  It shouldn't call
kref_put() while holding a spinlock.
Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/usb-serial.c

@@ -60,19 +60,19 @@ static struct usb_driver usb_serial_driver = {
 
 static int debug;
 static struct usb_serial *serial_table[SERIAL_TTY_MINORS];	/* initially all NULL */
-static spinlock_t table_lock;
+static DEFINE_MUTEX(table_lock);
 static LIST_HEAD(usb_serial_driver_list);
 
 struct usb_serial *usb_serial_get_by_index(unsigned index)
 {
 	struct usb_serial *serial;
 
-	spin_lock(&table_lock);
+	mutex_lock(&table_lock);
 	serial = serial_table[index];
 
 	if (serial)
 		kref_get(&serial->kref);
-	spin_unlock(&table_lock);
+	mutex_unlock(&table_lock);
 	return serial;
 }
 
@@ -84,7 +84,7 @@ static struct usb_serial *get_free_serial (struct usb_serial *serial, int num_po
 	dbg("%s %d", __FUNCTION__, num_ports);
 
 	*minor = 0;
-	spin_lock(&table_lock);
+	mutex_lock(&table_lock);
 	for (i = 0; i < SERIAL_TTY_MINORS; ++i) {
 		if (serial_table[i])
 			continue;
@@ -106,10 +106,10 @@ static struct usb_serial *get_free_serial (struct usb_serial *serial, int num_po
 			serial_table[i] = serial;
 			serial->port[j++]->number = i;
 		}
-		spin_unlock(&table_lock);
+		mutex_unlock(&table_lock);
 		return serial;
 	}
-	spin_unlock(&table_lock);
+	mutex_unlock(&table_lock);
 	return NULL;
 }
 
@@ -172,9 +172,9 @@ static void destroy_serial(struct kref *kref)
 
 void usb_serial_put(struct usb_serial *serial)
 {
-	spin_lock(&table_lock);
+	mutex_lock(&table_lock);
 	kref_put(&serial->kref, destroy_serial);
-	spin_unlock(&table_lock);
+	mutex_unlock(&table_lock);
 }
 
 /*****************************************************************************
@@ -1129,7 +1129,6 @@ static int __init usb_serial_init(void)
 		return -ENOMEM;
 
 	/* Initialize our global data */
-	spin_lock_init(&table_lock);
 	for (i = 0; i < SERIAL_TTY_MINORS; ++i) {
 		serial_table[i] = NULL;
 	}