tty: localise the lock

The termios and other changes mean the other protections needed on the driver
tty arrays should be adequate. Turn it all back on.

This contains pieces folded in from the fixes made to the original patches

| From: Geert Uytterhoeven <[e-mail]> (fix m68k)
| From: Paul Gortmaker <[e-mail]> (fix cris)
| From: Jiri Kosina <[e-mail]> (lockdep)
| From: Eric Dumazet <[e-mail]> (lockdep)

Signed-off-by: Alan Cox <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/amiserial.c

···
 	if (!retinfo)
 		return -EFAULT;
 	memset(&tmp, 0, sizeof(tmp));
-	tty_lock();
+	tty_lock(tty);
 	tmp.line = tty->index;
 	tmp.port = state->port;
 	tmp.flags = state->tport.flags;
···
 	tmp.close_delay = state->tport.close_delay;
 	tmp.closing_wait = state->tport.closing_wait;
 	tmp.custom_divisor = state->custom_divisor;
-	tty_unlock();
+	tty_unlock(tty);
 	if (copy_to_user(retinfo,&tmp,sizeof(*retinfo)))
 		return -EFAULT;
 	return 0;
···
 	if (copy_from_user(&new_serial,new_info,sizeof(new_serial)))
 		return -EFAULT;
 
-	tty_lock();
+	tty_lock(tty);
 	change_spd = ((new_serial.flags ^ port->flags) & ASYNC_SPD_MASK) ||
 		new_serial.custom_divisor != state->custom_divisor;
 	if (new_serial.irq || new_serial.port != state->port ||
 			new_serial.xmit_fifo_size != state->xmit_fifo_size) {
-		tty_unlock();
+		tty_unlock(tty);
 		return -EINVAL;
 	}
   
···
 		    (new_serial.xmit_fifo_size != state->xmit_fifo_size) ||
 		    ((new_serial.flags & ~ASYNC_USR_MASK) !=
 		     (port->flags & ~ASYNC_USR_MASK))) {
-			tty_unlock();
+			tty_unlock(tty);
 			return -EPERM;
 		}
 		port->flags = ((port->flags & ~ASYNC_USR_MASK) |
···
 	}
 
 	if (new_serial.baud_base < 9600) {
-		tty_unlock();
+		tty_unlock(tty);
 		return -EINVAL;
 	}
 
···
 		}
 	} else
 		retval = startup(tty, state);
-	tty_unlock();
+	tty_unlock(tty);
 	return retval;
 }
 

drivers/tty/cyclades.c

···
 	 * If the port is the middle of closing, bail out now
 	 */
 	if (tty_hung_up_p(filp) || (info->port.flags & ASYNC_CLOSING)) {
-		wait_event_interruptible_tty(info->port.close_wait,
+		wait_event_interruptible_tty(tty, info->port.close_wait,
 				!(info->port.flags & ASYNC_CLOSING));
 		return (info->port.flags & ASYNC_HUP_NOTIFY) ? -EAGAIN: -ERESTARTSYS;
 	}

drivers/tty/n_r3964.c

···
 
 	TRACE_L("read()");
 
-	tty_lock();
+	tty_lock(tty);
 
 	pClient = findClient(pInfo, task_pid(current));
 	if (pClient) {
···
 				goto unlock;
 			}
 			/* block until there is a message: */
-			wait_event_interruptible_tty(pInfo->read_wait,
+			wait_event_interruptible_tty(tty, pInfo->read_wait,
 					(pMsg = remove_msg(pInfo, pClient)));
 		}
 
···
 	}
 	ret = -EPERM;
 unlock:
-	tty_unlock();
+	tty_unlock(tty);
 	return ret;
 }
 
···
 	pHeader->locks = 0;
 	pHeader->owner = NULL;
 
-	tty_lock();
+	tty_lock(tty);
 
 	pClient = findClient(pInfo, task_pid(current));
 	if (pClient) {
···
 	add_tx_queue(pInfo, pHeader);
 	trigger_transmit(pInfo);
 
-	tty_unlock();
+	tty_unlock(tty);
 
 	return 0;
 }

drivers/tty/pty.c

···
 	wake_up_interruptible(&tty->read_wait);
 	wake_up_interruptible(&tty->write_wait);
 	tty->packet = 0;
+	/* Review - krefs on tty_link ?? */
 	if (!tty->link)
 		return;
 	tty->link->packet = 0;
···
 		        mutex_unlock(&devpts_mutex);
 		}
 #endif
-		tty_unlock();
+		tty_unlock(tty);
 		tty_vhangup(tty->link);
-		tty_lock();
+		tty_lock(tty);
 	}
 }
 
···
 		return retval;
 
 	/* find a device that is not in use. */
-	tty_lock();
+	mutex_lock(&devpts_mutex);
 	index = devpts_new_index(inode);
-	tty_unlock();
 	if (index < 0) {
 		retval = index;
 		goto err_file;
 	}
 
-	mutex_lock(&tty_mutex);
-	mutex_lock(&devpts_mutex);
-	tty = tty_init_dev(ptm_driver, index);
 	mutex_unlock(&devpts_mutex);
-	tty_lock();
-	mutex_unlock(&tty_mutex);
+
+	mutex_lock(&tty_mutex);
+	tty = tty_init_dev(ptm_driver, index);
 
 	if (IS_ERR(tty)) {
 		retval = PTR_ERR(tty);
 		goto out;
 	}
+
+	/* The tty returned here is locked so we can safely
+	   drop the mutex */
+	mutex_unlock(&tty_mutex);
 
 	set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 
···
 	if (retval)
 		goto err_release;
 
-	tty_unlock();
+	tty_unlock(tty);
 	return 0;
 err_release:
-	tty_unlock();
+	tty_unlock(tty);
 	tty_release(inode, filp);
 	return retval;
 out:
+	mutex_unlock(&tty_mutex);
 	devpts_kill_index(inode, index);
-	tty_unlock();
 err_file:
+        mutex_unlock(&devpts_mutex);
 	tty_free_file(filp);
 	return retval;
 }

drivers/tty/serial/crisv10.c

···
 	 */
 	if (tty_hung_up_p(filp) ||
 	    (info->flags & ASYNC_CLOSING)) {
-		wait_event_interruptible_tty(info->close_wait,
+		wait_event_interruptible_tty(tty, info->close_wait,
 			!(info->flags & ASYNC_CLOSING));
 #ifdef SERIAL_DO_RESTART
 		if (info->flags & ASYNC_HUP_NOTIFY)
···
 		printk("block_til_ready blocking: ttyS%d, count = %d\n",
 		       info->line, info->count);
 #endif
-		tty_unlock();
+		tty_unlock(tty);
 		schedule();
-		tty_lock();
+		tty_lock(tty);
 	}
 	set_current_state(TASK_RUNNING);
 	remove_wait_queue(&info->open_wait, &wait);
···
 	 */
 	if (tty_hung_up_p(filp) ||
 	    (info->flags & ASYNC_CLOSING)) {
-		wait_event_interruptible_tty(info->close_wait,
+		wait_event_interruptible_tty(tty, info->close_wait,
 			!(info->flags & ASYNC_CLOSING));
 #ifdef SERIAL_DO_RESTART
 		return ((info->flags & ASYNC_HUP_NOTIFY) ?

drivers/tty/synclink.c

···
 			printk("%s(%d):block_til_ready blocking on %s count=%d\n",
 				 __FILE__,__LINE__, tty->driver->name, port->count );
 				 
-		tty_unlock();
+		tty_unlock(tty);
 		schedule();
-		tty_lock();
+		tty_lock(tty);
 	}
 	
 	set_current_state(TASK_RUNNING);

drivers/tty/synclink_gt.c

···
 		}
 
 		DBGINFO(("%s block_til_ready wait\n", tty->driver->name));
-		tty_unlock();
+		tty_unlock(tty);
 		schedule();
-		tty_lock();
+		tty_lock(tty);
 	}
 
 	set_current_state(TASK_RUNNING);

drivers/tty/synclinkmp.c

···
 			printk("%s(%d):%s block_til_ready() count=%d\n",
 				 __FILE__,__LINE__, tty->driver->name, port->count );
 
-		tty_unlock();
+		tty_unlock(tty);
 		schedule();
-		tty_lock();
+		tty_lock(tty);
 	}
 
 	set_current_state(TASK_RUNNING);

drivers/tty/tty_io.c

···
 		put_device(tty->dev);
 	kfree(tty->write_buf);
 	tty_buffer_free_all(tty);
+	tty->magic = 0xDEADDEAD;
 	kfree(tty);
 }
 
···
 	}
 	spin_unlock(&redirect_lock);
 
-	tty_lock();
+	tty_lock(tty);
 
 	/* some functions below drop BTM, so we need this bit */
 	set_bit(TTY_HUPPING, &tty->flags);
···
 	clear_bit(TTY_HUPPING, &tty->flags);
 	tty_ldisc_enable(tty);
 
-	tty_unlock();
+	tty_unlock(tty);
 
 	if (f)
 		fput(f);
···
 {
 	if (tty) {
 		mutex_lock(&tty->atomic_write_lock);
-		tty_lock();
+		tty_lock(tty);
 		if (tty->ops->write && !test_bit(TTY_CLOSING, &tty->flags)) {
-			tty_unlock();
+			tty_unlock(tty);
 			tty->ops->write(tty, msg, strlen(msg));
 		} else
-			tty_unlock();
+			tty_unlock(tty);
 		tty_write_unlock(tty);
 	}
 	return;
···
 	}
 	initialize_tty_struct(tty, driver, idx);
 
+	tty_lock(tty);
 	retval = tty_driver_install_tty(driver, tty);
 	if (retval < 0)
 		goto err_deinit_tty;
···
 	retval = tty_ldisc_setup(tty, tty->link);
 	if (retval)
 		goto err_release_tty;
+	/* Return the tty locked so that it cannot vanish under the caller */
 	return tty;
 
 err_deinit_tty:
+	tty_unlock(tty);
 	deinitialize_tty_struct(tty);
 	free_tty_struct(tty);
 err_module_put:
···
 
 	/* call the tty release_tty routine to clean out this slot */
 err_release_tty:
+	tty_unlock(tty);
 	printk_ratelimited(KERN_INFO "tty_init_dev: ldisc open failed, "
 				 "clearing slot %d\n", idx);
 	release_tty(tty, idx);
···
 	if (tty_paranoia_check(tty, inode, __func__))
 		return 0;
 
-	tty_lock();
+	tty_lock(tty);
 	check_tty_count(tty, __func__);
 
 	__tty_fasync(-1, filp, 0);
···
 	pty_master = (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
 		      tty->driver->subtype == PTY_TYPE_MASTER);
 	devpts = (tty->driver->flags & TTY_DRIVER_DEVPTS_MEM) != 0;
+	/* Review: parallel close */
 	o_tty = tty->link;
 
 	if (tty_release_checks(tty, o_tty, idx)) {
-		tty_unlock();
+		tty_unlock(tty);
 		return 0;
 	}
 
···
 	if (tty->ops->close)
 		tty->ops->close(tty, filp);
 
-	tty_unlock();
+	tty_unlock(tty);
 	/*
 	 * Sanity check: if tty->count is going to zero, there shouldn't be
 	 * any waiters on tty->read_wait or tty->write_wait.  We test the
···
 		   opens on /dev/tty */
 
 		mutex_lock(&tty_mutex);
-		tty_lock();
+		tty_lock_pair(tty, o_tty);
 		tty_closing = tty->count <= 1;
 		o_tty_closing = o_tty &&
 			(o_tty->count <= (pty_master ? 1 : 0));
···
 
 		printk(KERN_WARNING "%s: %s: read/write wait queue active!\n",
 				__func__, tty_name(tty, buf));
-		tty_unlock();
+		tty_unlock_pair(tty, o_tty);
 		mutex_unlock(&tty_mutex);
 		schedule();
 	}
···
 	}
 
 	mutex_unlock(&tty_mutex);
-	tty_unlock();
+	tty_unlock_pair(tty, o_tty);
 	/* At this point the TTY_CLOSING flag should ensure a dead tty
 	   cannot be re-opened by a racing opener */
 
···
 	tty_ldisc_release(tty, o_tty);
 	/*
 	 * The release_tty function takes care of the details of clearing
-	 * the slots and preserving the termios structure.
+	 * the slots and preserving the termios structure. The tty_unlock_pair
+	 * should be safe as we keep a kref while the tty is locked (so the
+	 * unlock never unlocks a freed tty).
 	 */
 	mutex_lock(&tty_mutex);
 	release_tty(tty, idx);
···
 	/* Make this pty number available for reallocation */
 	if (devpts)
 		devpts_kill_index(inode, idx);
-
 	return 0;
 }
 
···
  *	Locking: tty_mutex protects tty, tty_lookup_driver and tty_init_dev.
  *		 tty->count should protect the rest.
  *		 ->siglock protects ->signal/->sighand
+ *
+ *	Note: the tty_unlock/lock cases without a ref are only safe due to
+ *	tty_mutex
  */
 
 static int tty_open(struct inode *inode, struct file *filp)
···
 	retval = 0;
 
 	mutex_lock(&tty_mutex);
-	tty_lock();
-
+	/* This is protected by the tty_mutex */
 	tty = tty_open_current_tty(device, filp);
 	if (IS_ERR(tty)) {
 		retval = PTR_ERR(tty);
···
 	}
 
 	if (tty) {
+		tty_lock(tty);
 		retval = tty_reopen(tty);
-		if (retval)
+		if (retval < 0) {
+			tty_unlock(tty);
 			tty = ERR_PTR(retval);
-	} else
+		}
+	} else	/* Returns with the tty_lock held for now */
 		tty = tty_init_dev(driver, index);
 
 	mutex_unlock(&tty_mutex);
 	if (driver)
 		tty_driver_kref_put(driver);
 	if (IS_ERR(tty)) {
-		tty_unlock();
 		retval = PTR_ERR(tty);
 		goto err_file;
 	}
···
 		printk(KERN_DEBUG "%s: error %d in opening %s...\n", __func__,
 				retval, tty->name);
 #endif
-		tty_unlock(); /* need to call tty_release without BTM */
+		tty_unlock(tty); /* need to call tty_release without BTM */
 		tty_release(inode, filp);
 		if (retval != -ERESTARTSYS)
 			return retval;
···
 		/*
 		 * Need to reset f_op in case a hangup happened.
 		 */
-		tty_lock();
 		if (filp->f_op == &hung_up_tty_fops)
 			filp->f_op = &tty_fops;
-		tty_unlock();
 		goto retry_open;
 	}
-	tty_unlock();
+	tty_unlock(tty);
 
 
 	mutex_lock(&tty_mutex);
-	tty_lock();
+	tty_lock(tty);
 	spin_lock_irq(&current->sighand->siglock);
 	if (!noctty &&
 	    current->signal->leader &&
···
 	    tty->session == NULL)
 		__proc_set_tty(current, tty);
 	spin_unlock_irq(&current->sighand->siglock);
-	tty_unlock();
+	tty_unlock(tty);
 	mutex_unlock(&tty_mutex);
 	return 0;
 err_unlock:
-	tty_unlock();
 	mutex_unlock(&tty_mutex);
 	/* after locks to avoid deadlock */
 	if (!IS_ERR_OR_NULL(driver))
···
 
 static int tty_fasync(int fd, struct file *filp, int on)
 {
+	struct tty_struct *tty = file_tty(filp);
 	int retval;
-	tty_lock();
+
+	tty_lock(tty);
 	retval = __tty_fasync(fd, filp, on);
-	tty_unlock();
+	tty_unlock(tty);
+
 	return retval;
 }
 
···
 	tty->pgrp = NULL;
 	tty->overrun_time = jiffies;
 	tty_buffer_init(tty);
+	mutex_init(&tty->legacy_mutex);
 	mutex_init(&tty->termios_mutex);
 	mutex_init(&tty->ldisc_mutex);
 	init_waitqueue_head(&tty->write_wait);

drivers/tty/tty_ldisc.c

···
 	if (IS_ERR(new_ldisc))
 		return PTR_ERR(new_ldisc);
 
-	tty_lock();
+	tty_lock(tty);
 	/*
 	 *	We need to look at the tty locking here for pty/tty pairs
 	 *	when both sides try to change in parallel.
···
 	 */
 
 	if (tty->ldisc->ops->num == ldisc) {
-		tty_unlock();
+		tty_unlock(tty);
 		tty_ldisc_put(new_ldisc);
 		return 0;
 	}
 
-	tty_unlock();
+	tty_unlock(tty);
 	/*
 	 *	Problem: What do we do if this blocks ?
 	 *	We could deadlock here
···
 
 	tty_wait_until_sent(tty, 0);
 
-	tty_lock();
+	tty_lock(tty);
 	mutex_lock(&tty->ldisc_mutex);
 
 	/*
···
 
 	while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) {
 		mutex_unlock(&tty->ldisc_mutex);
-		tty_unlock();
+		tty_unlock(tty);
 		wait_event(tty_ldisc_wait,
 			test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0);
-		tty_lock();
+		tty_lock(tty);
 		mutex_lock(&tty->ldisc_mutex);
 	}
 
···
 
 	o_ldisc = tty->ldisc;
 
-	tty_unlock();
+	tty_unlock(tty);
 	/*
 	 *	Make sure we don't change while someone holds a
 	 *	reference to the line discipline. The TTY_LDISC bit
···
 
 	retval = tty_ldisc_wait_idle(tty, 5 * HZ);
 
-	tty_lock();
+	tty_lock(tty);
 	mutex_lock(&tty->ldisc_mutex);
 
 	/* handle wait idle failure locked */
···
 		clear_bit(TTY_LDISC_CHANGING, &tty->flags);
 		mutex_unlock(&tty->ldisc_mutex);
 		tty_ldisc_put(new_ldisc);
-		tty_unlock();
+		tty_unlock(tty);
 		return -EIO;
 	}
 
···
 	if (o_work)
 		schedule_work(&o_tty->buf.work);
 	mutex_unlock(&tty->ldisc_mutex);
-	tty_unlock();
+	tty_unlock(tty);
 	return retval;
 }
 
···
 	 * need to wait for another function taking the BTM
 	 */
 	clear_bit(TTY_LDISC, &tty->flags);
-	tty_unlock();
+	tty_unlock(tty);
 	cancel_work_sync(&tty->buf.work);
 	mutex_unlock(&tty->ldisc_mutex);
 retry:
-	tty_lock();
+	tty_lock(tty);
 	mutex_lock(&tty->ldisc_mutex);
 
 	/* At this point we have a closed ldisc and we want to
···
 		if (atomic_read(&tty->ldisc->users) != 1) {
 			char cur_n[TASK_COMM_LEN], tty_n[64];
 			long timeout = 3 * HZ;
-			tty_unlock();
+			tty_unlock(tty);
 
 			while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) {
 				timeout = MAX_SCHEDULE_TIMEOUT;
···
 	tty_ldisc_enable(tty);
 	return 0;
 }
+
+static void tty_ldisc_kill(struct tty_struct *tty)
+{
+	mutex_lock(&tty->ldisc_mutex);
+	/*
+	 * Now kill off the ldisc
+	 */
+	tty_ldisc_close(tty, tty->ldisc);
+	tty_ldisc_put(tty->ldisc);
+	/* Force an oops if we mess this up */
+	tty->ldisc = NULL;
+
+	/* Ensure the next open requests the N_TTY ldisc */
+	tty_set_termios_ldisc(tty, N_TTY);
+	mutex_unlock(&tty->ldisc_mutex);
+}
+
 /**
  *	tty_ldisc_release		-	release line discipline
  *	@tty: tty being shut down
···
 	 * race with the set_ldisc code path.
 	 */
 
+	tty_lock_pair(tty, o_tty);
 	tty_ldisc_halt(tty);
 	tty_ldisc_flush_works(tty);
-	tty_lock();
-
-	mutex_lock(&tty->ldisc_mutex);
-	/*
-	 * Now kill off the ldisc
-	 */
-	tty_ldisc_close(tty, tty->ldisc);
-	tty_ldisc_put(tty->ldisc);
-	/* Force an oops if we mess this up */
-	tty->ldisc = NULL;
-
-	/* Ensure the next open requests the N_TTY ldisc */
-	tty_set_termios_ldisc(tty, N_TTY);
-	mutex_unlock(&tty->ldisc_mutex);
-
-	tty_unlock();
+	if (o_tty) {
+		tty_ldisc_halt(o_tty);
+		tty_ldisc_flush_works(o_tty);
+	}
 
 	/* This will need doing differently if we need to lock */
-	if (o_tty)
-		tty_ldisc_release(o_tty, NULL);
+	tty_ldisc_kill(tty);
 
+	if (o_tty)
+		tty_ldisc_kill(o_tty);
+
+	tty_unlock_pair(tty, o_tty);
 	/* And the memory resources remaining (buffers, termios) will be
 	   disposed of when the kref hits zero */
 }

drivers/tty/tty_mutex.c

···
 #include <linux/semaphore.h>
 #include <linux/sched.h>
 
-/*
- * The 'big tty mutex'
- *
- * This mutex is taken and released by tty_lock() and tty_unlock(),
- * replacing the older big kernel lock.
- * It can no longer be taken recursively, and does not get
- * released implicitly while sleeping.
- *
- * Don't use in new code.
- */
-static DEFINE_MUTEX(big_tty_mutex);
+/* Legacy tty mutex glue */
+
+enum {
+	TTY_MUTEX_NORMAL,
+	TTY_MUTEX_NESTED,
+};
 
 /*
  * Getting the big tty mutex.
  */
-void __lockfunc tty_lock(void)
+
+static void __lockfunc tty_lock_nested(struct tty_struct *tty,
+				       unsigned int subclass)
 {
-	mutex_lock(&big_tty_mutex);
+	if (tty->magic != TTY_MAGIC) {
+		printk(KERN_ERR "L Bad %p\n", tty);
+		WARN_ON(1);
+		return;
+	}
+	tty_kref_get(tty);
+	mutex_lock_nested(&tty->legacy_mutex, subclass);
+}
+
+void __lockfunc tty_lock(struct tty_struct *tty)
+{
+	return tty_lock_nested(tty, TTY_MUTEX_NORMAL);
 }
 EXPORT_SYMBOL(tty_lock);
 
-void __lockfunc tty_unlock(void)
+void __lockfunc tty_unlock(struct tty_struct *tty)
 {
-	mutex_unlock(&big_tty_mutex);
+	if (tty->magic != TTY_MAGIC) {
+		printk(KERN_ERR "U Bad %p\n", tty);
+		WARN_ON(1);
+		return;
+	}
+	mutex_unlock(&tty->legacy_mutex);
+	tty_kref_put(tty);
 }
 EXPORT_SYMBOL(tty_unlock);
+
+/*
+ * Getting the big tty mutex for a pair of ttys with lock ordering
+ * On a non pty/tty pair tty2 can be NULL which is just fine.
+ */
+void __lockfunc tty_lock_pair(struct tty_struct *tty,
+					struct tty_struct *tty2)
+{
+	if (tty < tty2) {
+		tty_lock(tty);
+		tty_lock_nested(tty2, TTY_MUTEX_NESTED);
+	} else {
+		if (tty2 && tty2 != tty)
+			tty_lock(tty2);
+		tty_lock_nested(tty, TTY_MUTEX_NESTED);
+	}
+}
+EXPORT_SYMBOL(tty_lock_pair);
+
+void __lockfunc tty_unlock_pair(struct tty_struct *tty,
+						struct tty_struct *tty2)
+{
+	tty_unlock(tty);
+	if (tty2 && tty2 != tty)
+		tty_unlock(tty2);
+}
+EXPORT_SYMBOL(tty_unlock_pair);

drivers/tty/tty_port.c

···
 
 	/* block if port is in the process of being closed */
 	if (tty_hung_up_p(filp) || port->flags & ASYNC_CLOSING) {
-		wait_event_interruptible_tty(port->close_wait,
+		wait_event_interruptible_tty(tty, port->close_wait,
 				!(port->flags & ASYNC_CLOSING));
 		if (port->flags & ASYNC_HUP_NOTIFY)
 			return -EAGAIN;
···
 			retval = -ERESTARTSYS;
 			break;
 		}
-		tty_unlock();
+		tty_unlock(tty);
 		schedule();
-		tty_lock();
+		tty_lock(tty);
 	}
 	finish_wait(&port->open_wait, &wait);
 

include/linux/tty.h

···
 	struct mutex ldisc_mutex;
 	struct tty_ldisc *ldisc;
 
+	struct mutex legacy_mutex;
 	struct mutex termios_mutex;
 	spinlock_t ctrl_lock;
 	/* Termios values are protected by the termios mutex */
···
 
 /* tty_mutex.c */
 /* functions for preparation of BKL removal */
-extern void __lockfunc tty_lock(void) __acquires(tty_lock);
-extern void __lockfunc tty_unlock(void) __releases(tty_lock);
+extern void __lockfunc tty_lock(struct tty_struct *tty);
+extern void __lockfunc tty_unlock(struct tty_struct *tty);
+extern void __lockfunc tty_lock_pair(struct tty_struct *tty,
+				struct tty_struct *tty2);
+extern void __lockfunc tty_unlock_pair(struct tty_struct *tty,
+				struct tty_struct *tty2);
 
 /*
  * this shall be called only from where BTM is held (like close)
···
 static inline void tty_wait_until_sent_from_close(struct tty_struct *tty,
 		long timeout)
 {
-	tty_unlock(); /* tty->ops->close holds the BTM, drop it while waiting */
+	tty_unlock(tty); /* tty->ops->close holds the BTM, drop it while waiting */
 	tty_wait_until_sent(tty, timeout);
-	tty_lock();
+	tty_lock(tty);
 }
 
 /*
···
  *
  * Do not use in new code.
  */
-#define wait_event_interruptible_tty(wq, condition)			\
+#define wait_event_interruptible_tty(tty, wq, condition)		\
 ({									\
 	int __ret = 0;							\
 	if (!(condition)) {						\
-		__wait_event_interruptible_tty(wq, condition, __ret);	\
+		__wait_event_interruptible_tty(tty, wq, condition, __ret);	\
 	}								\
 	__ret;								\
 })
 
-#define __wait_event_interruptible_tty(wq, condition, ret)		\
+#define __wait_event_interruptible_tty(tty, wq, condition, ret)		\
 do {									\
 	DEFINE_WAIT(__wait);						\
 									\
···
 		if (condition)						\
 			break;						\
 		if (!signal_pending(current)) {				\
-			tty_unlock();					\
+			tty_unlock(tty);					\
 			schedule();					\
-			tty_lock();					\
+			tty_lock(tty);					\
 			continue;					\
 		}							\
 		ret = -ERESTARTSYS;					\

net/bluetooth/rfcomm/tty.c

···
 			break;
 		}
 
-		tty_unlock();
+		tty_unlock(tty);
 		schedule();
-		tty_lock();
+		tty_lock(tty);
 	}
 	set_current_state(TASK_RUNNING);
 	remove_wait_queue(&dev->wait, &wait);