Input: keyboard - add locking around event handling

Keyboard input handler is multiplexing events form all keyboard-like
devices in the system. Because of that per-device lock provided by
input core is not enough to prevent clashes in ked_event() and we
need our own lock to ensure that only one thread at a time executing
kbd_event().
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/char/keyboard.c

@@ -132,6 +132,7 @@ int shift_state = 0;
  */
 
 static struct input_handler kbd_handler;
+static DEFINE_SPINLOCK(kbd_event_lock);
 static unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];	/* keyboard key bitmap */
 static unsigned char shift_down[NR_SHIFT];		/* shift state counters.. */
 static int dead_key_next;
@@ -1296,10 +1297,16 @@ static void kbd_keycode(unsigned int keycode, int down, int hw_raw)
 static void kbd_event(struct input_handle *handle, unsigned int event_type,
 		      unsigned int event_code, int value)
 {
+	/* We are called with interrupts disabled, just take the lock */
+	spin_lock(&kbd_event_lock);
+
 	if (event_type == EV_MSC && event_code == MSC_RAW && HW_RAW(handle->dev))
 		kbd_rawcode(value);
 	if (event_type == EV_KEY)
 		kbd_keycode(event_code, value, HW_RAW(handle->dev));
+
+	spin_unlock(&kbd_event_lock);
+
 	tasklet_schedule(&keyboard_tasklet);
 	do_poke_blanked_console = 1;
 	schedule_console_callback();