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tty: BKL pushdown

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- 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>
This commit is contained in:
Alan Cox
2008-04-30 00:53:29 -07:00
committed by Linus Torvalds
parent e523844260
commit 04f378b198
9 changed files with 149 additions and 53 deletions
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6
drivers/char/tty_ioctl.c
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@ -395,6 +395,7 @@ static void change_termios(struct tty_struct *tty, struct ktermios *new_termios)
int canon_change;
struct ktermios old_termios = *tty->termios;
struct tty_ldisc *ld;
unsigned long flags;
/*
* Perform the actual termios internal changes under lock.
@ -429,11 +430,13 @@ static void change_termios(struct tty_struct *tty, struct ktermios *new_termios)
STOP_CHAR(tty) == '\023' &&
START_CHAR(tty) == '\021');
if (old_flow != new_flow) {
spin_lock_irqsave(&tty->ctrl_lock, flags);
tty->ctrl_status &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
if (new_flow)
tty->ctrl_status |= TIOCPKT_DOSTOP;
else
tty->ctrl_status |= TIOCPKT_NOSTOP;
spin_unlock_irqrestore(&tty->ctrl_lock, flags);
wake_up_interruptible(&tty->link->read_wait);
}
}
@ -905,6 +908,7 @@ int n_tty_ioctl(struct tty_struct *tty, struct file *file,
unsigned int cmd, unsigned long arg)
{
struct tty_struct *real_tty;
unsigned long flags;
int retval;
if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
@ -963,6 +967,7 @@ int n_tty_ioctl(struct tty_struct *tty, struct file *file,
return -ENOTTY;
if (get_user(pktmode, (int __user *) arg))
return -EFAULT;
spin_lock_irqsave(&tty->ctrl_lock, flags);
if (pktmode) {
if (!tty->packet) {
tty->packet = 1;
@ -970,6 +975,7 @@ int n_tty_ioctl(struct tty_struct *tty, struct file *file,
}
} else
tty->packet = 0;
spin_unlock_irqrestore(&tty->ctrl_lock, flags);
return 0;
}
default: