tty: BKL pushdown

- Push the BKL down into the line disciplines
- Switch the tty layer to unlocked_ioctl
- Introduce a new ctrl_lock spin lock for the control bits
- Eliminate much of the lock_kernel use in n_tty
- Prepare to (but don't yet) call the drivers with the lock dropped
  on the paths that historically held the lock

BKL now primarily protects open/close/ldisc change in the tty layer

[jirislaby@gmail.com: a couple of fixes]
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/drivers/char/vt.c b/drivers/char/vt.c
index 1c2660477135..e64f0bf3624e 100644
--- a/drivers/char/vt.c
+++ b/drivers/char/vt.c
@@ -2541,6 +2541,9 @@ int tioclinux(struct tty_struct *tty, unsigned long arg)
         if (get_user(type, p))
                 return -EFAULT;
         ret = 0;
+
+        lock_kernel();
+
         switch (type)
         {
                 case TIOCL_SETSEL:
@@ -2560,7 +2563,7 @@ int tioclinux(struct tty_struct *tty, unsigned long arg)
                         ret = sel_loadlut(p);
                         break;
                 case TIOCL_GETSHIFTSTATE:
-                        
+
         /*
          * Make it possible to react to Shift+Mousebutton.
          * Note that 'shift_state' is an undocumented
@@ -2615,6 +2618,7 @@ int tioclinux(struct tty_struct *tty, unsigned long arg)
                         ret = -EINVAL;
                         break;
         }
+        unlock_kernel();
         return ret;
 }
 
@@ -3829,7 +3833,7 @@ static int con_font_get(struct vc_data *vc, struct console_font_op *op)
                 goto out;
 
         c = (font.width+7)/8 * 32 * font.charcount;
-        
+
         if (op->data && font.charcount > op->charcount)
                 rc = -ENOSPC;
         if (!(op->flags & KD_FONT_FLAG_OLD)) {