--- a/master/cdev.c	Mon Jun 30 15:51:46 2008 +0000
+++ b/master/cdev.c	Tue Jul 01 15:38:20 2008 +0000
@@ -138,8 +138,8 @@
         EC_DBG("ioctl(filp = %x, cmd = %u (%u), arg = %x)\n",
                 (u32) filp, (u32) cmd, (u32) _IOC_NR(cmd), (u32) arg);
 
-    // FIXME lock
-    
+    down(&master->master_sem);
+
     switch (cmd) {
         case EC_IOCTL_MASTER:
             {
@@ -1012,6 +1012,7 @@
             retval = -ENOTTY;
     }
 
+    up(&master->master_sem);
     return retval;
 }