tty: Push the lock down further into the ldisc code

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 9 insertions, 3 deletions

diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c
index d914e77f7f01..3f653f7d849f 100644
--- a/drivers/char/tty_ldisc.c
+++ b/drivers/char/tty_ldisc.c
@@ -445,8 +445,14 @@ static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
 static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
 {
         WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags));
-        if (ld->ops->open)
-                return ld->ops->open(tty);
+        if (ld->ops->open) {
+                int ret;
+                /* BKL here locks verus a hangup event */
+                lock_kernel();
+                ret = ld->ops->open(tty);
+                unlock_kernel();
+                return ret;
+        }
         return 0;
 }
 
@@ -566,6 +572,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
                 return 0;
         }
 
+        unlock_kernel();
         /*
          *      Problem: What do we do if this blocks ?
          *      We could deadlock here
@@ -573,7 +580,6 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
 
         tty_wait_until_sent(tty, 0);
 
-        unlock_kernel();
         mutex_lock(&tty->ldisc_mutex);
 
         /*