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, 2 insertions, 2 deletions

diff --git a/include/linux/tty.h b/include/linux/tty.h
index 265831ccaa88..4d3702bade03 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -183,6 +183,7 @@ struct tty_struct {
         int index;
         struct tty_ldisc ldisc;
         struct mutex termios_mutex;
+        spinlock_t ctrl_lock;
         struct ktermios *termios, *termios_locked;
         char name[64];
         struct pid *pgrp;
@@ -323,8 +324,7 @@ extern void tty_ldisc_put(int);
 extern void tty_wakeup(struct tty_struct *tty);
 extern void tty_ldisc_flush(struct tty_struct *tty);
 
-extern int tty_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
-                     unsigned long arg);
+extern long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
 extern int tty_mode_ioctl(struct tty_struct *tty, struct file *file,
                         unsigned int cmd, unsigned long arg);
 extern int tty_perform_flush(struct tty_struct *tty, unsigned long arg);