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Commit 2febdb63 authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
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tty: Preset lock subclass for nested tty locks 



Eliminate the requirement of specifying the tty lock nesting at
lock time; instead, set the lock subclass for slave ptys at pty
install (normal ttys and master ptys use subclass 0).

Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 2aff5e2b

drivers/tty/pty.c

+2 −0
Original line number Diff line number Diff line
@@ -399,6 +399,8 @@ static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty, 
	if (!o_tty)

		goto err_put_module;



	tty_set_lock_subclass(o_tty);



	if (legacy) {

		/* We always use new tty termios data so we can do this

		   the easy way .. */

drivers/tty/tty_mutex.c

+9 −10
Original line number Diff line number Diff line
@@ -13,15 +13,14 @@ 


enum {

	TTY_MUTEX_NORMAL,

	TTY_MUTEX_NESTED,

	TTY_MUTEX_SLAVE,

};



/*

 * Getting the big tty mutex.

 */



static void __lockfunc tty_lock_nested(struct tty_struct *tty,

				       unsigned int subclass)

void __lockfunc tty_lock(struct tty_struct *tty)

{

	if (tty->magic != TTY_MAGIC) {

		pr_err("L Bad %p\n", tty);
@@ -29,12 +28,7 @@ static void __lockfunc tty_lock_nested(struct tty_struct *tty, 
		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);

	mutex_lock(&tty->legacy_mutex);

}

EXPORT_SYMBOL(tty_lock);
@@ -56,7 +50,7 @@ void __lockfunc tty_lock_slave(struct tty_struct *tty) 
		WARN_ON(!mutex_is_locked(&tty->link->legacy_mutex) ||

			!tty->driver->type == TTY_DRIVER_TYPE_PTY ||

			!tty->driver->type == PTY_TYPE_SLAVE);

		tty_lock_nested(tty, TTY_MUTEX_NESTED);

		tty_lock(tty);

	}

}
@@ -65,3 +59,8 @@ void __lockfunc tty_unlock_slave(struct tty_struct *tty) 
	if (tty && tty != tty->link)

		tty_unlock(tty);

}



void tty_set_lock_subclass(struct tty_struct *tty)

{

	lockdep_set_subclass(&tty->legacy_mutex, TTY_MUTEX_SLAVE);

}

include/linux/tty.h

+1 −0
Original line number Diff line number Diff line
@@ -640,6 +640,7 @@ extern void __lockfunc tty_lock(struct tty_struct *tty); 
extern void __lockfunc tty_unlock(struct tty_struct *tty);

extern void __lockfunc tty_lock_slave(struct tty_struct *tty);

extern void __lockfunc tty_unlock_slave(struct tty_struct *tty);

extern void tty_set_lock_subclass(struct tty_struct *tty);

/*

 * this shall be called only from where BTM is held (like close)

 *