Merge tag 'iwlwifi-next-for-kalle-2014-12-30' of https://git.kernel.org/pub/scm/linux...

[cascardo/linux.git] / drivers / tty / tty_mutex.c

diff --git a/drivers/tty/tty_mutex.c b/drivers/tty/tty_mutex.c
index 2e41abe..4486741 100644 (file)
--- a/drivers/tty/tty_mutex.c
+++ b/drivers/tty/tty_mutex.c
@@ -4,19 +4,23 @@
 #include <linux/semaphore.h>
 #include <linux/sched.h>
 
+/*
+ * Nested tty locks are necessary for releasing pty pairs.
+ * The stable lock order is master pty first, then slave pty.
+ */
+
 /* Legacy tty mutex glue */
 
 enum {
        TTY_MUTEX_NORMAL,
-       TTY_MUTEX_NESTED,
+       TTY_MUTEX_SLAVE,
 };
 
 /*
  * Getting the big tty mutex.
  */
 
-static void __lockfunc tty_lock_nested(struct tty_struct *tty,
-                                      unsigned int subclass)
+void __lockfunc tty_lock(struct tty_struct *tty)
 {
        if (tty->magic != TTY_MAGIC) {
                pr_err("L Bad %p\n", tty);
@@ -24,12 +28,7 @@ static void __lockfunc tty_lock_nested(struct tty_struct *tty,
                return;
        }
        tty_kref_get(tty);
-       mutex_lock_nested(&tty->legacy_mutex, subclass);
-}
-
-void __lockfunc tty_lock(struct tty_struct *tty)
-{
-       return tty_lock_nested(tty, TTY_MUTEX_NORMAL);
+       mutex_lock(&tty->legacy_mutex);
 }
 EXPORT_SYMBOL(tty_lock);
 
@@ -45,29 +44,23 @@ void __lockfunc tty_unlock(struct tty_struct *tty)
 }
 EXPORT_SYMBOL(tty_unlock);
 
-/*
- * Getting the big tty mutex for a pair of ttys with lock ordering
- * On a non pty/tty pair tty2 can be NULL which is just fine.
- */
-void __lockfunc tty_lock_pair(struct tty_struct *tty,
-                                       struct tty_struct *tty2)
+void __lockfunc tty_lock_slave(struct tty_struct *tty)
 {
-       if (tty < tty2) {
+       if (tty && tty != tty->link) {
+               WARN_ON(!mutex_is_locked(&tty->link->legacy_mutex) ||
+                       !tty->driver->type == TTY_DRIVER_TYPE_PTY ||
+                       !tty->driver->type == PTY_TYPE_SLAVE);
                tty_lock(tty);
-               tty_lock_nested(tty2, TTY_MUTEX_NESTED);
-       } else {
-               if (tty2 && tty2 != tty)
-                       tty_lock(tty2);
-               tty_lock_nested(tty, TTY_MUTEX_NESTED);
        }
 }
-EXPORT_SYMBOL(tty_lock_pair);
 
-void __lockfunc tty_unlock_pair(struct tty_struct *tty,
-                                               struct tty_struct *tty2)
+void __lockfunc tty_unlock_slave(struct tty_struct *tty)
+{
+       if (tty && tty != tty->link)
+               tty_unlock(tty);
+}
+
+void tty_set_lock_subclass(struct tty_struct *tty)
 {
-       tty_unlock(tty);
-       if (tty2 && tty2 != tty)
-               tty_unlock(tty2);
+       lockdep_set_subclass(&tty->legacy_mutex, TTY_MUTEX_SLAVE);
 }
-EXPORT_SYMBOL(tty_unlock_pair);