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Commit f0de0e8d authored by Linus Torvalds's avatar Linus Torvalds Committed by Live-CD User
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tty-ldisc: make /proc/tty/ldiscs use ldisc_ops instead of ldiscs 



The /proc/tty/ldiscs file is totally and utterly un-interested in the
"struct tty_ldisc" structures, and only cares about the underlying ldisc
operations.

So don't make it create a dummy 'struct ldisc' only to get a pointer to
the operations, and then destroy it.  Instead, we split up the function
'tty_ldisc_try_get()', and create a 'get_ldops()' helper that just looks
up the ldisc operations based on the ldisc number.

That makes the code simpler to read (smaller and more well-defined
helper functions), and allows the /proc functions to avoid creating that
useless dummy only to immediately free it again.

Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Tested-by: default avatarSergey Senozhatsky <sergey.senozhatsky@mail.by>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 7a4b2310

drivers/char/tty_ldisc.c

+39 −26
Original line number Diff line number Diff line
@@ -145,6 +145,34 @@ int tty_unregister_ldisc(int disc) 
}

EXPORT_SYMBOL(tty_unregister_ldisc);



static struct tty_ldisc_ops *get_ldops(int disc)

{

	unsigned long flags;

	struct tty_ldisc_ops *ldops, *ret;



	spin_lock_irqsave(&tty_ldisc_lock, flags);

	ret = ERR_PTR(-EINVAL);

	ldops = tty_ldiscs[disc];

	if (ldops) {

		ret = ERR_PTR(-EAGAIN);

		if (try_module_get(ldops->owner)) {

			ldops->refcount++;

			ret = ldops;

		}

	}

	spin_unlock_irqrestore(&tty_ldisc_lock, flags);

	return ret;

}



static void put_ldops(struct tty_ldisc_ops *ldops)

{

	unsigned long flags;



	spin_lock_irqsave(&tty_ldisc_lock, flags);

	ldops->refcount--;

	module_put(ldops->owner);

	spin_unlock_irqrestore(&tty_ldisc_lock, flags);

}



/**

 *	tty_ldisc_try_get	-	try and reference an ldisc
@@ -156,36 +184,21 @@ EXPORT_SYMBOL(tty_unregister_ldisc); 


static struct tty_ldisc *tty_ldisc_try_get(int disc)

{

	unsigned long flags;

	struct tty_ldisc *ld;

	struct tty_ldisc_ops *ldops;

	int err = -EINVAL;



	ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL);

	if (ld == NULL)

		return ERR_PTR(-ENOMEM);



	spin_lock_irqsave(&tty_ldisc_lock, flags);

	ld->ops = NULL;

	ldops = tty_ldiscs[disc];

	/* Check the entry is defined */

	if (ldops) {

		/* If the module is being unloaded we can't use it */

		if (!try_module_get(ldops->owner))

			err = -EAGAIN;

		else {

			/* lock it */

			ldops->refcount++;

			ld->ops = ldops;

			atomic_set(&ld->users, 1);

			err = 0;

		}

	}

	spin_unlock_irqrestore(&tty_ldisc_lock, flags);

	if (err) {

	ldops = get_ldops(disc);

	if (IS_ERR(ldops)) {

		kfree(ld);

		return ERR_PTR(err);

		return ERR_CAST(ldops);

	}



	ld->ops = ldops;

	atomic_set(&ld->users, 1);

	return ld;

}
@@ -234,13 +247,13 @@ static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) 
static int tty_ldiscs_seq_show(struct seq_file *m, void *v)

{

	int i = *(loff_t *)v;

	struct tty_ldisc *ld;

	struct tty_ldisc_ops *ldops;



	ld = tty_ldisc_try_get(i);

	if (IS_ERR(ld))

	ldops = get_ldops(i);

	if (IS_ERR(ldops))

		return 0;

	seq_printf(m, "%-10s %2d\n", ld->ops->name ? ld->ops->name : "???", i);

	put_ldisc(ld);

	seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i);

	put_ldops(ldops);

	return 0;

}