tty: replace BKL with a new tty_lock

As a preparation for replacing the big kernel lock
in the TTY layer, wrap all the callers in new
macros tty_lock, tty_lock_nested and tty_unlock.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 13 insertions, 11 deletions

diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c
index 500e740ec5e4..97681ffd6cbd 100644
--- a/drivers/char/tty_ldisc.c
+++ b/drivers/char/tty_ldisc.c
@@ -440,6 +440,8 @@ static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
  *
  *      A helper opening method. Also a convenient debugging and check
  *      point.
+ *
+ *      Locking: always called with BTM already held.
  */
 
 static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
@@ -447,10 +449,10 @@ 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) {
                 int ret;
-                /* BKL here locks verus a hangup event */
-                lock_kernel();
+                /* BTM here locks versus a hangup event */
+                tty_lock_nested(); /* always held here already */
                 ret = ld->ops->open(tty);
-                unlock_kernel();
+                tty_unlock();
                 return ret;
         }
         return 0;
@@ -553,7 +555,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
         if (IS_ERR(new_ldisc))
                 return PTR_ERR(new_ldisc);
 
-        lock_kernel();
+        tty_lock();
         /*
          *      We need to look at the tty locking here for pty/tty pairs
          *      when both sides try to change in parallel.
@@ -567,12 +569,12 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
          */
 
         if (tty->ldisc->ops->num == ldisc) {
-                unlock_kernel();
+                tty_unlock();
                 tty_ldisc_put(new_ldisc);
                 return 0;
         }
 
-        unlock_kernel();
+        tty_unlock();
         /*
          *      Problem: What do we do if this blocks ?
          *      We could deadlock here
@@ -594,7 +596,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
                 mutex_lock(&tty->ldisc_mutex);
         }
 
-        lock_kernel();
+        tty_lock();
 
         set_bit(TTY_LDISC_CHANGING, &tty->flags);
 
@@ -607,7 +609,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
 
         o_ldisc = tty->ldisc;
 
-        unlock_kernel();
+        tty_unlock();
         /*
          *      Make sure we don't change while someone holds a
          *      reference to the line discipline. The TTY_LDISC bit
@@ -633,14 +635,14 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
         flush_scheduled_work();
 
         mutex_lock(&tty->ldisc_mutex);
-        lock_kernel();
+        tty_lock();
         if (test_bit(TTY_HUPPED, &tty->flags)) {
                 /* We were raced by the hangup method. It will have stomped
                    the ldisc data and closed the ldisc down */
                 clear_bit(TTY_LDISC_CHANGING, &tty->flags);
                 mutex_unlock(&tty->ldisc_mutex);
                 tty_ldisc_put(new_ldisc);
-                unlock_kernel();
+                tty_unlock();
                 return -EIO;
         }
 
@@ -682,7 +684,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
         if (o_work)
                 schedule_delayed_work(&o_tty->buf.work, 1);
         mutex_unlock(&tty->ldisc_mutex);
-        unlock_kernel();
+        tty_unlock();
         return retval;
 }