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path: root/drivers/tty/tty_mutex.c
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Diffstat (limited to 'drivers/tty/tty_mutex.c')
-rw-r--r--drivers/tty/tty_mutex.c49
1 files changed, 21 insertions, 28 deletions
diff --git a/drivers/tty/tty_mutex.c b/drivers/tty/tty_mutex.c
index 2e41abebbcba..4486741190c4 100644
--- 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);