Commit 19475209 authored by Jiri Slaby's avatar Jiri Slaby Committed by Greg Kroah-Hartman
Browse files

tty: drop tty_ldisc_ops::refcount 



The refcount is checked only in tty_unregister_ldisc and EBUSY returned
if it is nonzero. But none of the tty_unregister_ldisc callers act
anyhow if this (or any other) error is returned. So remove
tty_ldisc_ops::refcount completely and make tty_unregister_ldisc return
'void' in the next patches. That means we assume tty_unregister_ldisc is
not called while the ldisc might be in use. That relies on
try_module_get in get_ldops and module_put in put_ldops.

Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210505091928.22010-18-jslaby@suse.cz


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent f81ee8b8

drivers/tty/n_tty.c

+1 −1
Original line number Diff line number Diff line
@@ -2450,7 +2450,7 @@ void n_tty_inherit_ops(struct tty_ldisc_ops *ops) 
{

	*ops = n_tty_ops;

	ops->owner = NULL;

	ops->refcount = ops->flags = 0;

	ops->flags = 0;

}

EXPORT_SYMBOL_GPL(n_tty_inherit_ops);

drivers/tty/tty_ldisc.c

+3 −11
Original line number Diff line number Diff line
@@ -69,7 +69,6 @@ int tty_register_ldisc(struct tty_ldisc_ops *new_ldisc) 


	raw_spin_lock_irqsave(&tty_ldiscs_lock, flags);

	tty_ldiscs[new_ldisc->num] = new_ldisc;

	new_ldisc->refcount = 0;

	raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags);



	return ret;
@@ -90,16 +89,12 @@ EXPORT_SYMBOL(tty_register_ldisc); 
int tty_unregister_ldisc(struct tty_ldisc_ops *ldisc)

{

	unsigned long flags;

	int ret = 0;



	raw_spin_lock_irqsave(&tty_ldiscs_lock, flags);

	if (tty_ldiscs[ldisc->num]->refcount)

		ret = -EBUSY;

	else

	tty_ldiscs[ldisc->num] = NULL;

	raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags);



	return ret;

	return 0;

}

EXPORT_SYMBOL(tty_unregister_ldisc);
@@ -113,11 +108,9 @@ static struct tty_ldisc_ops *get_ldops(int disc) 
	ldops = tty_ldiscs[disc];

	if (ldops) {

		ret = ERR_PTR(-EAGAIN);

		if (try_module_get(ldops->owner)) {

			ldops->refcount++;

		if (try_module_get(ldops->owner))

			ret = ldops;

	}

	}

	raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags);

	return ret;

}
@@ -127,7 +120,6 @@ static void put_ldops(struct tty_ldisc_ops *ldops) 
	unsigned long flags;



	raw_spin_lock_irqsave(&tty_ldiscs_lock, flags);

	ldops->refcount--;

	module_put(ldops->owner);

	raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags);

}

include/linux/tty_ldisc.h

+0 −2
Original line number Diff line number Diff line
@@ -208,8 +208,6 @@ struct tty_ldisc_ops { 
				const char *fp, int count);



	struct  module *owner;



	int refcount;

};



struct tty_ldisc {