The following commit make console open fails while booting:

	commit d966976924119acd35a431adbb95292082f73f8c
	Author: Alan Cox <alan@linux.intel.com>
	Date:   Tue Aug 11 10:23:05 2009 +1000

	tty: make the kref destructor occur asynchronously

Due to tty release routines runs in workqueue now, error like following
will be reported while booting:

INIT open /dev/console Input/output error

The reason is that now there's latency issue with closing, but when we
open a "closing not finished" tty, -EIO will be returned.

Fix it as alan's following suggestion:

Fun but its actually not a bug and the fix is wrong in itself as the port
may be closing but not yet being destructed, in which case it seems to do
the wrong thing.  Opening a tty that is closing (and could be closing for
long periods) is supposed to return -EIO.

I suspect a better way to deal with this and keep the old console timing
is to split tty->shutdown into two functions.

tty->shutdown() - called synchronously just before we dump the tty onto
the waitqueue for destruction

tty->cleanup() - called when the destructor runs.

We would then do the shutdown part which can occur in IRQ context fine,
before queueing the rest of the release (from tty->magic = 0 ...  the end)
to occur asynchronously

The USB update in -next would then need a call like

       if (tty->cleanup)
               tty->cleanup(tty);

at the top of the async function and the USB shutdown to be split between
shutdown and cleanup as the USB resource cleanup and final tidy cannot
occur synchronously as it needs to sleep.

In other words the logic becomes

       final kref put
               make object unfindable

       async
               clean it up
Signed-off-by: Dave Young <hidave.darkstar@gmail.com>
Cc: Greg KH <greg@kroah.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Emmanuel Benisty <benisty.e@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

drivers/char/tty_io.c

@@ -1389,7 +1389,7 @@ EXPORT_SYMBOL(tty_shutdown);
  *	of ttys that the driver keeps.
  *
  *	This method gets called from a work queue so that the driver private
- *	shutdown ops can sleep (needed for USB at least)
+ *	cleanup ops can sleep (needed for USB at least)
  */
 static void release_one_tty(struct work_struct *work)
 {
@@ -1397,10 +1397,9 @@ static void release_one_tty(struct work_struct *work)
 		container_of(work, struct tty_struct, hangup_work);
 	struct tty_driver *driver = tty->driver;
 
-	if (tty->ops->shutdown)
-		tty->ops->shutdown(tty);
-	else
-		tty_shutdown(tty);
+	if (tty->ops->cleanup)
+		tty->ops->cleanup(tty);
+
 	tty->magic = 0;
 	tty_driver_kref_put(driver);
 	module_put(driver->owner);
@@ -1415,6 +1414,12 @@ static void release_one_tty(struct work_struct *work)
 static void queue_release_one_tty(struct kref *kref)
 {
 	struct tty_struct *tty = container_of(kref, struct tty_struct, kref);
+
+	if (tty->ops->shutdown)
+		tty->ops->shutdown(tty);
+	else
+		tty_shutdown(tty);
+
 	/* The hangup queue is now free so we can reuse it rather than
 	   waste a chunk of memory for each port */
 	INIT_WORK(&tty->hangup_work, release_one_tty);

drivers/usb/serial/usb-serial.c

@@ -1269,7 +1269,7 @@ static const struct tty_operations serial_ops = {
 	.chars_in_buffer =	serial_chars_in_buffer,
 	.tiocmget =		serial_tiocmget,
 	.tiocmset =		serial_tiocmset,
-	.shutdown = 		serial_do_free,
+	.cleanup = 		serial_do_free,
 	.install = 		serial_install,
 	.proc_fops =		&serial_proc_fops,
 };

include/linux/tty_driver.h

@@ -45,8 +45,16 @@
  *
  * void (*shutdown)(struct tty_struct * tty);
  *
- * 	This routine is called when a particular tty device is closed for
- *	the last time freeing up the resources.
+ * 	This routine is called synchronously when a particular tty device
+ *	is closed for the last time freeing up the resources.
+ *
+ *
+ * void (*cleanup)(struct tty_struct * tty);
+ *
+ *	This routine is called asynchronously when a particular tty device
+ *	is closed for the last time freeing up the resources. This is
+ *	actually the second part of shutdown for routines that might sleep.
+ *
  *
  * int (*write)(struct tty_struct * tty,
  * 		 const unsigned char *buf, int count);
@@ -233,6 +241,7 @@ struct tty_operations {
 	int  (*open)(struct tty_struct * tty, struct file * filp);
 	void (*close)(struct tty_struct * tty, struct file * filp);
 	void (*shutdown)(struct tty_struct *tty);
+	void (*cleanup)(struct tty_struct *tty);
 	int  (*write)(struct tty_struct * tty,
 		      const unsigned char *buf, int count);
 	int  (*put_char)(struct tty_struct *tty, unsigned char ch);