USB: Push BKL on open down into the drivers

Straightforward push into the drivers to allow
auditing individual drivers separately

Signed-off-by: Oliver Neukum <oliver@neukum.org>
Acked-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/hid/usbhid/hiddev.c b/drivers/hid/usbhid/hiddev.c
index 867e084..433602a 100644 (file)
--- a/drivers/hid/usbhid/hiddev.c
+++ b/drivers/hid/usbhid/hiddev.c
@@ -265,9 +265,10 @@ static int hiddev_release(struct inode * inode, struct file * file)
 static int hiddev_open(struct inode *inode, struct file *file)
 {
        struct hiddev_list *list;
-       int res;
+       int res, i;
 
-       int i = iminor(inode) - HIDDEV_MINOR_BASE;
+       lock_kernel();
+       i = iminor(inode) - HIDDEV_MINOR_BASE;
 
        if (i >= HIDDEV_MINORS || i < 0 || !hiddev_table[i])
                return -ENODEV;
@@ -313,10 +314,12 @@ static int hiddev_open(struct inode *inode, struct file *file)
                        usbhid_open(hid);
                }
 
+       unlock_kernel();
        return 0;
 bail:
        file->private_data = NULL;
        kfree(list);
+       unlock_kernel();
        return res;
 }
 

diff --git a/drivers/media/video/dabusb.c b/drivers/media/video/dabusb.c
index 9b413a3..0f50508 100644 (file)
--- a/drivers/media/video/dabusb.c
+++ b/drivers/media/video/dabusb.c
@@ -616,10 +616,12 @@ static int dabusb_open (struct inode *inode, struct file *file)
 {
        int devnum = iminor(inode);
        pdabusb_t s;
+       int r;
 
        if (devnum < DABUSB_MINOR || devnum >= (DABUSB_MINOR + NRDABUSB))
                return -EIO;
 
+       lock_kernel();
        s = &dabusb[devnum - DABUSB_MINOR];
 
        dbg("dabusb_open");
@@ -634,6 +636,7 @@ static int dabusb_open (struct inode *inode, struct file *file)
                msleep_interruptible(500);
 
                if (signal_pending (current)) {
+                       unlock_kernel();
                        return -EAGAIN;
                }
                mutex_lock(&s->mutex);
@@ -641,6 +644,7 @@ static int dabusb_open (struct inode *inode, struct file *file)
        if (usb_set_interface (s->usbdev, _DABUSB_IF, 1) < 0) {
                mutex_unlock(&s->mutex);
                dev_err(&s->usbdev->dev, "set_interface failed\n");
+               unlock_kernel();
                return -EINVAL;
        }
        s->opened = 1;
@@ -649,7 +653,9 @@ static int dabusb_open (struct inode *inode, struct file *file)
        file->f_pos = 0;
        file->private_data = s;
 
-       return nonseekable_open(inode, file);
+       r = nonseekable_open(inode, file);
+       unlock_kernel();
+       return r;
 }
 
 static int dabusb_release (struct inode *inode, struct file *file)

diff --git a/drivers/staging/frontier/alphatrack.c b/drivers/staging/frontier/alphatrack.c
index 15aed87..e2f82f0 100644 (file)
--- a/drivers/staging/frontier/alphatrack.c
+++ b/drivers/staging/frontier/alphatrack.c
@@ -41,6 +41,7 @@
 #include <linux/mutex.h>
 
 #include <linux/uaccess.h>
+#include <linux/smp_lock.h>
 #include <linux/input.h>
 #include <linux/usb.h>
 #include <linux/poll.h>
@@ -325,6 +326,7 @@ static int usb_alphatrack_open(struct inode *inode, struct file *file)
        int retval = 0;
        struct usb_interface *interface;
 
+       lock_kernel();
        nonseekable_open(inode, file);
        subminor = iminor(inode);
 
@@ -394,6 +396,7 @@ unlock_exit:
 
 unlock_disconnect_exit:
        mutex_unlock(&disconnect_mutex);
+       unlock_kernel();
 
        return retval;
 }

diff --git a/drivers/staging/frontier/tranzport.c b/drivers/staging/frontier/tranzport.c
index ef8fcc8..1d3f7dc 100644 (file)
--- a/drivers/staging/frontier/tranzport.c
+++ b/drivers/staging/frontier/tranzport.c
@@ -40,6 +40,7 @@
 #include <linux/mutex.h>
 
 #include <linux/uaccess.h>
+#include <linux/smp_lock.h>
 #include <linux/input.h>
 #include <linux/usb.h>
 #include <linux/poll.h>
@@ -343,6 +344,7 @@ static int usb_tranzport_open(struct inode *inode, struct file *file)
        int retval = 0;
        struct usb_interface *interface;
 
+       lock_kernel();
        nonseekable_open(inode, file);
        subminor = iminor(inode);
 
@@ -413,6 +415,7 @@ unlock_exit:
 
 unlock_disconnect_exit:
        mutex_unlock(&disconnect_mutex);
+       unlock_kernel();
 
        return retval;
 }

diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index 18aafcb..b75a3d8 100644 (file)
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -19,6 +19,7 @@
 #include <linux/uaccess.h>
 #include <linux/bitops.h>
 #include <linux/poll.h>
+#include <linux/smp_lock.h>
 #include <linux/usb.h>
 #include <linux/usb/cdc.h>
 #include <asm/byteorder.h>
@@ -516,6 +517,7 @@ static int wdm_open(struct inode *inode, struct file *file)
        struct usb_interface *intf;
        struct wdm_device *desc;
 
+       lock_kernel();
        mutex_lock(&wdm_mutex);
        intf = usb_find_interface(&wdm_driver, minor);
        if (!intf)
@@ -548,6 +550,7 @@ static int wdm_open(struct inode *inode, struct file *file)
        usb_autopm_put_interface(desc->intf);
 out:
        mutex_unlock(&wdm_mutex);
+       unlock_kernel();
        return rv;
 }
 

diff --git a/drivers/usb/class/usblp.c b/drivers/usb/class/usblp.c
index 93b5f85..d53f949 100644 (file)
--- a/drivers/usb/class/usblp.c
+++ b/drivers/usb/class/usblp.c
@@ -56,6 +56,7 @@
 #include <linux/slab.h>
 #include <linux/lp.h>
 #include <linux/mutex.h>
+#include <linux/smp_lock.h>
 #undef DEBUG
 #include <linux/usb.h>
 
@@ -395,6 +396,7 @@ static int usblp_open(struct inode *inode, struct file *file)
        if (minor < 0)
                return -ENODEV;
 
+       lock_kernel();
        mutex_lock (&usblp_mutex);
 
        retval = -ENODEV;
@@ -434,6 +436,7 @@ static int usblp_open(struct inode *inode, struct file *file)
        }
 out:
        mutex_unlock (&usblp_mutex);
+       unlock_kernel();
        return retval;
 }
 

diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
index 8588c09..426bfc7 100644 (file)
--- a/drivers/usb/class/usbtmc.c
+++ b/drivers/usb/class/usbtmc.c
@@ -26,6 +26,7 @@
 #include <linux/uaccess.h>
 #include <linux/kref.h>
 #include <linux/mutex.h>
+#include <linux/smp_lock.h>
 #include <linux/usb.h>
 #include <linux/usb/tmc.h>
 
@@ -113,6 +114,7 @@ static int usbtmc_open(struct inode *inode, struct file *filp)
        struct usbtmc_device_data *data;
        int retval = 0;
 
+       lock_kernel();
        intf = usb_find_interface(&usbtmc_driver, iminor(inode));
        if (!intf) {
                printk(KERN_ERR KBUILD_MODNAME
@@ -128,6 +130,7 @@ static int usbtmc_open(struct inode *inode, struct file *filp)
        filp->private_data = data;
 
 exit:
+       unlock_kernel();
        return retval;
 }
 

diff --git a/drivers/usb/core/file.c b/drivers/usb/core/file.c
index bfc6c2e..c3536f1 100644 (file)
--- a/drivers/usb/core/file.c
+++ b/drivers/usb/core/file.c
@@ -34,7 +34,6 @@ static int usb_open(struct inode * inode, struct file * file)
        int err = -ENODEV;
        const struct file_operations *old_fops, *new_fops = NULL;
 
-       lock_kernel();
        down_read(&minor_rwsem);
        c = usb_minors[minor];
 
@@ -53,7 +52,6 @@ static int usb_open(struct inode * inode, struct file * file)
        fops_put(old_fops);
  done:
        up_read(&minor_rwsem);
-       unlock_kernel();
        return err;
 }
 

diff --git a/drivers/usb/image/mdc800.c b/drivers/usb/image/mdc800.c
index e192e8f..dce4f7b 100644 (file)
--- a/drivers/usb/image/mdc800.c
+++ b/drivers/usb/image/mdc800.c
@@ -96,6 +96,7 @@
 #include <linux/module.h>
 #include <linux/wait.h>
 #include <linux/mutex.h>
+#include <linux/smp_lock.h>
 
 #include <linux/usb.h>
 #include <linux/fs.h>
@@ -622,6 +623,7 @@ static int mdc800_device_open (struct inode* inode, struct file *file)
        int retval=0;
        int errn=0;
 
+       lock_kernel();
        mutex_lock(&mdc800->io_lock);
        
        if (mdc800->state == NOT_CONNECTED)
@@ -660,6 +662,7 @@ static int mdc800_device_open (struct inode* inode, struct file *file)
 
 error_out:
        mutex_unlock(&mdc800->io_lock);
+       unlock_kernel();
        return errn;
 }
 

diff --git a/drivers/usb/misc/adutux.c b/drivers/usb/misc/adutux.c
index 306e978..ac8ad91 100644 (file)
--- a/drivers/usb/misc/adutux.c
+++ b/drivers/usb/misc/adutux.c
@@ -25,6 +25,7 @@
 #include <linux/module.h>
 #include <linux/usb.h>
 #include <linux/mutex.h>
+#include <linux/smp_lock.h>
 #include <asm/uaccess.h>
 
 #ifdef CONFIG_USB_DEBUG
@@ -274,6 +275,7 @@ static int adu_open(struct inode *inode, struct file *file)
 
        dbg(2,"%s : enter", __func__);
 
+       lock_kernel();
        subminor = iminor(inode);
 
        if ((retval = mutex_lock_interruptible(&adutux_mutex))) {
@@ -332,6 +334,7 @@ static int adu_open(struct inode *inode, struct file *file)
 exit_no_device:
        mutex_unlock(&adutux_mutex);
 exit_no_lock:
+       unlock_kernel();
        dbg(2,"%s : leave, return value %d ", __func__, retval);
        return retval;
 }

diff --git a/drivers/usb/misc/ftdi-elan.c b/drivers/usb/misc/ftdi-elan.c
index f21bf51..32c47fb 100644 (file)
--- a/drivers/usb/misc/ftdi-elan.c
+++ b/drivers/usb/misc/ftdi-elan.c
@@ -45,6 +45,7 @@
 #include <linux/module.h>
 #include <linux/kref.h>
 #include <linux/mutex.h>
+#include <linux/smp_lock.h>
 #include <asm/uaccess.h>
 #include <linux/usb.h>
 #include <linux/workqueue.h>
@@ -623,22 +624,30 @@ static void ftdi_elan_status_work(struct work_struct *work)
 */
 static int ftdi_elan_open(struct inode *inode, struct file *file)
 {
-        int subminor = iminor(inode);
-        struct usb_interface *interface = usb_find_interface(&ftdi_elan_driver,
-                subminor);
+       int subminor;
+       struct usb_interface *interface;
+
+       lock_kernel();
+        subminor = iminor(inode);
+        interface = usb_find_interface(&ftdi_elan_driver, subminor);
+
         if (!interface) {
+               unlock_kernel();
                 printk(KERN_ERR "can't find device for minor %d\n", subminor);
                 return -ENODEV;
         } else {
                 struct usb_ftdi *ftdi = usb_get_intfdata(interface);
                 if (!ftdi) {
+                       unlock_kernel();
                         return -ENODEV;
                 } else {
                         if (down_interruptible(&ftdi->sw_lock)) {
+                               unlock_kernel();
                                 return -EINTR;
                         } else {
                                 ftdi_elan_get_kref(ftdi);
                                 file->private_data = ftdi;
+                               unlock_kernel();
                                 return 0;
                         }
                 }

diff --git a/drivers/usb/misc/idmouse.c b/drivers/usb/misc/idmouse.c
index a54c3cb..68df9ac 100644 (file)
--- a/drivers/usb/misc/idmouse.c
+++ b/drivers/usb/misc/idmouse.c
@@ -24,6 +24,7 @@
 #include <linux/module.h>
 #include <linux/completion.h>
 #include <linux/mutex.h>
+#include <linux/smp_lock.h>
 #include <asm/uaccess.h>
 #include <linux/usb.h>
 
@@ -226,16 +227,20 @@ static int idmouse_open(struct inode *inode, struct file *file)
        struct usb_interface *interface;
        int result;
 
+       lock_kernel();
        /* get the interface from minor number and driver information */
        interface = usb_find_interface (&idmouse_driver, iminor (inode));
-       if (!interface)
+       if (!interface) {
+               unlock_kernel();
                return -ENODEV;
+       }
 
        mutex_lock(&open_disc_mutex);
        /* get the device information block from the interface */
        dev = usb_get_intfdata(interface);
        if (!dev) {
                mutex_unlock(&open_disc_mutex);
+               unlock_kernel();
                return -ENODEV;
        }
 
@@ -272,6 +277,7 @@ error:
 
        /* unlock this device */
        mutex_unlock(&dev->lock);
+       unlock_kernel();
        return result;
 }
 

diff --git a/drivers/usb/misc/iowarrior.c b/drivers/usb/misc/iowarrior.c
index 5206423..d3c8523 100644 (file)
--- a/drivers/usb/misc/iowarrior.c
+++ b/drivers/usb/misc/iowarrior.c
@@ -602,10 +602,12 @@ static int iowarrior_open(struct inode *inode, struct file *file)
 
        dbg("%s", __func__);
 
+       lock_kernel();
        subminor = iminor(inode);
 
        interface = usb_find_interface(&iowarrior_driver, subminor);
        if (!interface) {
+               unlock_kernel();
                err("%s - error, can't find device for minor %d", __func__,
                    subminor);
                return -ENODEV;
@@ -615,6 +617,7 @@ static int iowarrior_open(struct inode *inode, struct file *file)
        dev = usb_get_intfdata(interface);
        if (!dev) {
                mutex_unlock(&iowarrior_open_disc_lock);
+               unlock_kernel();
                return -ENODEV;
        }
 
@@ -641,6 +644,7 @@ static int iowarrior_open(struct inode *inode, struct file *file)
 
 out:
        mutex_unlock(&dev->mutex);
+       unlock_kernel();
        return retval;
 }
 

diff --git a/drivers/usb/misc/ldusb.c b/drivers/usb/misc/ldusb.c
index 7c0bd13..8de32df 100644 (file)
--- a/drivers/usb/misc/ldusb.c
+++ b/drivers/usb/misc/ldusb.c
@@ -33,6 +33,7 @@
 #include <linux/slab.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
+#include <linux/smp_lock.h>
 
 #include <asm/uaccess.h>
 #include <linux/input.h>
@@ -296,12 +297,14 @@ static int ld_usb_open(struct inode *inode, struct file *file)
        int retval;
        struct usb_interface *interface;
 
+       lock_kernel();
        nonseekable_open(inode, file);
        subminor = iminor(inode);
 
        interface = usb_find_interface(&ld_usb_driver, subminor);
 
        if (!interface) {
+               unlock_kernel();
                err("%s - error, can't find device for minor %d\n",
                     __func__, subminor);
                return -ENODEV;
@@ -309,12 +312,16 @@ static int ld_usb_open(struct inode *inode, struct file *file)
 
        dev = usb_get_intfdata(interface);
 
-       if (!dev)
+       if (!dev) {
+               unlock_kernel();
                return -ENODEV;
+       }
 
        /* lock this device */
-       if (mutex_lock_interruptible(&dev->mutex))
+       if (mutex_lock_interruptible(&dev->mutex)) {
+               unlock_kernel();
                return -ERESTARTSYS;
+       }
 
        /* allow opening only once */
        if (dev->open_count) {
@@ -353,6 +360,7 @@ static int ld_usb_open(struct inode *inode, struct file *file)
 
 unlock_exit:
        mutex_unlock(&dev->mutex);
+       unlock_kernel();
 
        return retval;
 }

diff --git a/drivers/usb/misc/legousbtower.c b/drivers/usb/misc/legousbtower.c
index 3d4378f..94e1b84 100644 (file)
--- a/drivers/usb/misc/legousbtower.c
+++ b/drivers/usb/misc/legousbtower.c
@@ -82,6 +82,7 @@
 #include <linux/module.h>
 #include <linux/completion.h>
 #include <linux/mutex.h>
+#include <linux/smp_lock.h>
 #include <asm/uaccess.h>
 #include <linux/usb.h>
 #include <linux/poll.h>
@@ -345,6 +346,7 @@ static int tower_open (struct inode *inode, struct file *file)
 
        dbg(2, "%s: enter", __func__);
 
+       lock_kernel();
        nonseekable_open(inode, file);
        subminor = iminor(inode);
 
@@ -430,6 +432,7 @@ unlock_exit:
        mutex_unlock(&dev->lock);
 
 exit:
+       unlock_kernel();
        dbg(2, "%s: leave, return value %d ", __func__, retval);
 
        return retval;

diff --git a/drivers/usb/misc/rio500.c b/drivers/usb/misc/rio500.c
index 17e4eec..47ce46b 100644 (file)
--- a/drivers/usb/misc/rio500.c
+++ b/drivers/usb/misc/rio500.c
@@ -77,7 +77,7 @@ static struct rio_usb_data rio_instance;
 static int open_rio(struct inode *inode, struct file *file)
 {
        struct rio_usb_data *rio = &rio_instance;
-
+       lock_kernel();
        mutex_lock(&(rio->lock));
 
        if (rio->isopen || !rio->present) {
@@ -91,6 +91,7 @@ static int open_rio(struct inode *inode, struct file *file)
        mutex_unlock(&(rio->lock));
 
        dev_info(&rio->rio_dev->dev, "Rio opened.\n");
+       unlock_kernel();
 
        return 0;
 }

diff --git a/drivers/usb/misc/sisusbvga/sisusb.c b/drivers/usb/misc/sisusbvga/sisusb.c
index bb0b315..3991655 100644 (file)
--- a/drivers/usb/misc/sisusbvga/sisusb.c
+++ b/drivers/usb/misc/sisusbvga/sisusb.c
@@ -2416,21 +2416,28 @@ sisusb_open(struct inode *inode, struct file *file)
        struct usb_interface *interface;
        int subminor = iminor(inode);
 
-       if (!(interface = usb_find_interface(&sisusb_driver, subminor)))
+       lock_kernel();
+       if (!(interface = usb_find_interface(&sisusb_driver, subminor))) {
+               unlock_kernel();
                return -ENODEV;
+       }
 
-       if (!(sisusb = usb_get_intfdata(interface)))
+       if (!(sisusb = usb_get_intfdata(interface))) {
+               unlock_kernel();
                return -ENODEV;
+       }
 
        mutex_lock(&sisusb->lock);
 
        if (!sisusb->present || !sisusb->ready) {
                mutex_unlock(&sisusb->lock);
+               unlock_kernel();
                return -ENODEV;
        }
 
        if (sisusb->isopen) {
                mutex_unlock(&sisusb->lock);
+               unlock_kernel();
                return -EBUSY;
        }
 
@@ -2439,11 +2446,13 @@ sisusb_open(struct inode *inode, struct file *file)
                        if (sisusb_init_gfxdevice(sisusb, 0)) {
                                mutex_unlock(&sisusb->lock);
                                dev_err(&sisusb->sisusb_dev->dev, "Failed to initialize device\n");
+                               unlock_kernel();
                                return -EIO;
                        }
                } else {
                        mutex_unlock(&sisusb->lock);
                        dev_err(&sisusb->sisusb_dev->dev, "Device not attached to USB 2.0 hub\n");
+                       unlock_kernel();
                        return -EIO;
                }
        }
@@ -2456,6 +2465,7 @@ sisusb_open(struct inode *inode, struct file *file)
        file->private_data = sisusb;
 
        mutex_unlock(&sisusb->lock);
+       unlock_kernel();
 
        return 0;
 }

diff --git a/drivers/usb/misc/usblcd.c b/drivers/usb/misc/usblcd.c
index 499d750..90aede9 100644 (file)
--- a/drivers/usb/misc/usblcd.c
+++ b/drivers/usb/misc/usblcd.c
@@ -74,10 +74,12 @@ static int lcd_open(struct inode *inode, struct file *file)
        struct usb_interface *interface;
        int subminor, r;
 
+       lock_kernel();
        subminor = iminor(inode);
 
        interface = usb_find_interface(&lcd_driver, subminor);
        if (!interface) {
+               unlock_kernel();
                err ("USBLCD: %s - error, can't find device for minor %d",
                     __func__, subminor);
                return -ENODEV;
@@ -87,6 +89,7 @@ static int lcd_open(struct inode *inode, struct file *file)
        dev = usb_get_intfdata(interface);
        if (!dev) {
                mutex_unlock(&open_disc_mutex);
+               unlock_kernel();
                return -ENODEV;
        }
 
@@ -98,11 +101,13 @@ static int lcd_open(struct inode *inode, struct file *file)
        r = usb_autopm_get_interface(interface);
        if (r < 0) {
                kref_put(&dev->kref, lcd_delete);
+               unlock_kernel();
                return r;
        }
 
        /* save our object in the file's private structure */
        file->private_data = dev;
+       unlock_kernel();
 
        return 0;
 }

diff --git a/drivers/usb/misc/vstusb.c b/drivers/usb/misc/vstusb.c
index 874c81b..b787b25 100644 (file)
--- a/drivers/usb/misc/vstusb.c
+++ b/drivers/usb/misc/vstusb.c
@@ -27,6 +27,7 @@
 #include <linux/slab.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
+#include <linux/smp_lock.h>
 #include <linux/uaccess.h>
 #include <linux/usb.h>
 
@@ -103,19 +104,23 @@ static int vstusb_open(struct inode *inode, struct file *file)
        struct vstusb_device *vstdev;
        struct usb_interface *interface;
 
+       lock_kernel();
        interface = usb_find_interface(&vstusb_driver, iminor(inode));
 
        if (!interface) {
                printk(KERN_ERR KBUILD_MODNAME
                       ": %s - error, can't find device for minor %d\n",
                       __func__, iminor(inode));
+               unlock_kernel();
                return -ENODEV;
        }
 
        vstdev = usb_get_intfdata(interface);
 
-       if (!vstdev)
+       if (!vstdev) {
+               unlock_kernel();
                return -ENODEV;
+       }
 
        /* lock this device */
        mutex_lock(&vstdev->lock);
@@ -123,6 +128,7 @@ static int vstusb_open(struct inode *inode, struct file *file)
        /* can only open one time */
        if ((!vstdev->present) || (vstdev->isopen)) {
                mutex_unlock(&vstdev->lock);
+               unlock_kernel();
                return -EBUSY;
        }
 
@@ -137,6 +143,7 @@ static int vstusb_open(struct inode *inode, struct file *file)
        dev_dbg(&vstdev->usb_dev->dev, "%s: opened\n", __func__);
 
        mutex_unlock(&vstdev->lock);
+       unlock_kernel();
 
        return 0;
 }

diff --git a/drivers/usb/usb-skeleton.c b/drivers/usb/usb-skeleton.c
index 6152278..e94176b 100644 (file)
--- a/drivers/usb/usb-skeleton.c
+++ b/drivers/usb/usb-skeleton.c
@@ -18,6 +18,7 @@
 #include <linux/slab.h>
 #include <linux/module.h>
 #include <linux/kref.h>
+#include <linux/smp_lock.h>
 #include <linux/uaccess.h>
 #include <linux/usb.h>
 #include <linux/mutex.h>
@@ -90,6 +91,7 @@ static int skel_open(struct inode *inode, struct file *file)
        int subminor;
        int retval = 0;
 
+       lock_kernel();
        subminor = iminor(inode);
 
        interface = usb_find_interface(&skel_driver, subminor);
@@ -135,6 +137,7 @@ static int skel_open(struct inode *inode, struct file *file)
        mutex_unlock(&dev->io_mutex);
 
 exit:
+       unlock_kernel();
        return retval;
 }