1 files changed, 15 insertions, 11 deletions

diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c
index 913aa8d3f1c5..acd76b767d4c 100644
--- a/drivers/char/tty_ldisc.c
+++ b/drivers/char/tty_ldisc.c
@@ -21,7 +21,6 @@
 #include <linux/proc_fs.h>
 #include <linux/init.h>
 #include <linux/module.h>
-#include <linux/smp_lock.h>
 #include <linux/device.h>
 #include <linux/wait.h>
 #include <linux/bitops.h>
@@ -791,17 +790,20 @@ void tty_ldisc_hangup(struct tty_struct *tty)
          * N_TTY.
          */
         if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) {
-                /* Avoid racing set_ldisc */
+                /* Avoid racing set_ldisc or tty_ldisc_release */
                 mutex_lock(&tty->ldisc_mutex);
-                /* Switch back to N_TTY */
-                tty_ldisc_halt(tty);
-                tty_ldisc_wait_idle(tty);
-                tty_ldisc_reinit(tty);
-                /* At this point we have a closed ldisc and we want to
-                   reopen it. We could defer this to the next open but
-                   it means auditing a lot of other paths so this is a FIXME */
-                WARN_ON(tty_ldisc_open(tty, tty->ldisc));
-                tty_ldisc_enable(tty);
+                if (tty->ldisc) {       /* Not yet closed */
+                        /* Switch back to N_TTY */
+                        tty_ldisc_halt(tty);
+                        tty_ldisc_wait_idle(tty);
+                        tty_ldisc_reinit(tty);
+                        /* At this point we have a closed ldisc and we want to
+                           reopen it. We could defer this to the next open but
+                           it means auditing a lot of other paths so this is
+                           a FIXME */
+                        WARN_ON(tty_ldisc_open(tty, tty->ldisc));
+                        tty_ldisc_enable(tty);
+                }
                 mutex_unlock(&tty->ldisc_mutex);
                 tty_reset_termios(tty);
         }
@@ -866,6 +868,7 @@ void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
 
         tty_ldisc_wait_idle(tty);
 
+        mutex_lock(&tty->ldisc_mutex);
         /*
          * Now kill off the ldisc
          */
@@ -876,6 +879,7 @@ void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
 
         /* Ensure the next open requests the N_TTY ldisc */
         tty_set_termios_ldisc(tty, N_TTY);
+        mutex_unlock(&tty->ldisc_mutex);
 
         /* This will need doing differently if we need to lock */
         if (o_tty)