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Commit 18eac1cc authored by Linus Torvalds's avatar Linus Torvalds Committed by Greg Kroah-Hartman
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tty-ldisc: make refcount be atomic_t 'users' count 



This is pure preparation of changing the ldisc reference counting to be
a true refcount that defines the lifetime of the ldisc.  But this is a
purely syntactic change for now to make the next steps easier.

This patch should make no semantic changes at all. But I wanted to make
the ldisc refcount be an atomic (I will be touching it without locks
soon enough), and I wanted to rename it so that there isn't quite as
much confusion between 'ldo->refcount' (ldisk operations refcount) and
'ld->refcount' (ldisc refcount itself) in the same file.

So it's now an atomic 'ld->users' count. It still starts at zero,
despite having a reference from 'tty->ldisc', but that will change once
we turn it into a _real_ refcount.

Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Tested-by: default avatarOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Tested-by: default avatarSergey Senozhatsky <sergey.senozhatsky@mail.by>
Acked-by: default avatarAlan Cox <alan@linux.intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent a33a052f

drivers/char/tty_ldisc.c

+8 −10
Original line number Original line Diff line number Diff line
@@ -142,7 +142,7 @@ static struct tty_ldisc *tty_ldisc_try_get(int disc) 
			/* lock it */

			/* lock it */

			ldops->refcount++;

			ldops->refcount++;

			ld->ops = ldops;

			ld->ops = ldops;

			ld->refcount = 0;

			atomic_set(&ld->users, 0);

			err = 0;

			err = 0;

		}

		}

	}

	}
@@ -206,7 +206,7 @@ static void tty_ldisc_put(struct tty_ldisc *ld) 
	ldo->refcount--;

	ldo->refcount--;

	module_put(ldo->owner);

	module_put(ldo->owner);

	spin_unlock_irqrestore(&tty_ldisc_lock, flags);

	spin_unlock_irqrestore(&tty_ldisc_lock, flags);

	WARN_ON(ld->refcount);

	WARN_ON(atomic_read(&ld->users));

	kfree(ld);

	kfree(ld);

}

}
@@ -297,7 +297,7 @@ static int tty_ldisc_try(struct tty_struct *tty) 
	spin_lock_irqsave(&tty_ldisc_lock, flags);

	spin_lock_irqsave(&tty_ldisc_lock, flags);

	ld = tty->ldisc;

	ld = tty->ldisc;

	if (test_bit(TTY_LDISC, &tty->flags)) {

	if (test_bit(TTY_LDISC, &tty->flags)) {

		ld->refcount++;

		atomic_inc(&ld->users);

		ret = 1;

		ret = 1;

	}

	}

	spin_unlock_irqrestore(&tty_ldisc_lock, flags);

	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
@@ -324,7 +324,7 @@ struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) 
{

{

	/* wait_event is a macro */

	/* wait_event is a macro */

	wait_event(tty_ldisc_wait, tty_ldisc_try(tty));

	wait_event(tty_ldisc_wait, tty_ldisc_try(tty));

	WARN_ON(tty->ldisc->refcount == 0);

	WARN_ON(atomic_read(&tty->ldisc->users) == 0);

	return tty->ldisc;

	return tty->ldisc;

}

}

EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);

EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);
@@ -365,11 +365,9 @@ void tty_ldisc_deref(struct tty_ldisc *ld) 
	BUG_ON(ld == NULL);

	BUG_ON(ld == NULL);





	spin_lock_irqsave(&tty_ldisc_lock, flags);

	spin_lock_irqsave(&tty_ldisc_lock, flags);

	if (ld->refcount == 0)

	if (atomic_read(&ld->users) == 0)

		printk(KERN_ERR "tty_ldisc_deref: no references.\n");

		printk(KERN_ERR "tty_ldisc_deref: no references.\n");

	else

	else if (atomic_dec_and_test(&ld->users))

		ld->refcount--;

	if (ld->refcount == 0)

		wake_up(&tty_ldisc_wait);

		wake_up(&tty_ldisc_wait);

	spin_unlock_irqrestore(&tty_ldisc_lock, flags);

	spin_unlock_irqrestore(&tty_ldisc_lock, flags);

}

}
@@ -536,10 +534,10 @@ static int tty_ldisc_wait_idle(struct tty_struct *tty) 
{

{

	unsigned long flags;

	unsigned long flags;

	spin_lock_irqsave(&tty_ldisc_lock, flags);

	spin_lock_irqsave(&tty_ldisc_lock, flags);

	while (tty->ldisc->refcount) {

	while (atomic_read(&tty->ldisc->users)) {

		spin_unlock_irqrestore(&tty_ldisc_lock, flags);

		spin_unlock_irqrestore(&tty_ldisc_lock, flags);

		if (wait_event_timeout(tty_ldisc_wait,

		if (wait_event_timeout(tty_ldisc_wait,

				tty->ldisc->refcount == 0, 5 * HZ) == 0)

				atomic_read(&tty->ldisc->users) == 0, 5 * HZ) == 0)

			return -EBUSY;

			return -EBUSY;

		spin_lock_irqsave(&tty_ldisc_lock, flags);

		spin_lock_irqsave(&tty_ldisc_lock, flags);

	}

	}

include/linux/tty_ldisc.h

+1 −1
Original line number Original line Diff line number Diff line
@@ -144,7 +144,7 @@ struct tty_ldisc_ops { 




struct tty_ldisc {

struct tty_ldisc {

	struct tty_ldisc_ops *ops;

	struct tty_ldisc_ops *ops;

	int refcount;

	atomic_t users;

};

};





#define TTY_LDISC_MAGIC	0x5403

#define TTY_LDISC_MAGIC	0x5403