Input: serio - fix potential deadlock when unbinding drivers

sysfs_remove_group() waits for sysfs attributes to be removed, therefore
we do not need to worry about driver-specific attributes being accessed
after driver has been detached from the device. In fact, attempts to take
serio->drv_mutex in attribute methods may lead to the following deadlock:

                                          sysfs_read_file()
                                            fill_read_buffer()
                                              sysfs_get_active_two()
                                                psmouse_attr_show_helper()
                                                  serio_pin_driver()
serio_disconnect_driver()
  mutex_lock(&serio->drv_mutex);
                                <-------->        mutex_lock(&serio_drv_mutex);
    psmouse_disconnect()
      sysfs_remove_group(... psmouse_attr_group);
        ....
        sysfs_deactivate();
          wait_for_completion();

Fix this by removing calls to serio_[un]pin_driver() and functions themselves
and using driver-private mutexes to serialize access to attribute's set()
methods that may change device state.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

1 files changed, 0 insertions, 19 deletions

diff --git a/include/linux/serio.h b/include/linux/serio.h
index e2f3044..813d26c 100644
--- a/include/linux/serio.h
+++ b/include/linux/serio.h
@@ -136,25 +136,6 @@ static inline void serio_continue_rx(struct serio *serio)
 	spin_unlock_irq(&serio->lock);
 }
 
-/*
- * Use the following functions to pin serio's driver in process context
- */
-static inline int serio_pin_driver(struct serio *serio)
-{
-	return mutex_lock_interruptible(&serio->drv_mutex);
-}
-
-static inline void serio_pin_driver_uninterruptible(struct serio *serio)
-{
-	mutex_lock(&serio->drv_mutex);
-}
-
-static inline void serio_unpin_driver(struct serio *serio)
-{
-	mutex_unlock(&serio->drv_mutex);
-}
-
-
 #endif
 
 /*