linux/drivers/tty/tty_mutex.c
Peter Hurley 2febdb632b 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: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-11-05 18:50:42 -08:00

67 lines
1.3 KiB
C

#include <linux/tty.h>
#include <linux/module.h>
#include <linux/kallsyms.h>
#include <linux/semaphore.h>
#include <linux/sched.h>
/*
* Nested tty locks are necessary for releasing pty pairs.
* The stable lock order is master pty first, then slave pty.
*/
/* Legacy tty mutex glue */
enum {
TTY_MUTEX_NORMAL,
TTY_MUTEX_SLAVE,
};
/*
* Getting the big tty mutex.
*/
void __lockfunc tty_lock(struct tty_struct *tty)
{
if (tty->magic != TTY_MAGIC) {
pr_err("L Bad %p\n", tty);
WARN_ON(1);
return;
}
tty_kref_get(tty);
mutex_lock(&tty->legacy_mutex);
}
EXPORT_SYMBOL(tty_lock);
void __lockfunc tty_unlock(struct tty_struct *tty)
{
if (tty->magic != TTY_MAGIC) {
pr_err("U Bad %p\n", tty);
WARN_ON(1);
return;
}
mutex_unlock(&tty->legacy_mutex);
tty_kref_put(tty);
}
EXPORT_SYMBOL(tty_unlock);
void __lockfunc tty_lock_slave(struct tty_struct *tty)
{
if (tty && tty != tty->link) {
WARN_ON(!mutex_is_locked(&tty->link->legacy_mutex) ||
!tty->driver->type == TTY_DRIVER_TYPE_PTY ||
!tty->driver->type == PTY_TYPE_SLAVE);
tty_lock(tty);
}
}
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);
}