tty: Make lock subclasses available for other tty locks

Besides nested legacy_mutex locking which is required on pty pair
teardown, other nested pty operations require lock subclassing.

Move lock subclass definition to tty interface header, include/linux/tty.h,
and document its use.

Signed-off-by: Peter Hurley <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
This commit is contained in:
Peter Hurley 2015-01-17 15:42:04 -05:00 • committed by Greg Kroah-Hartman
commit 3abf87cd3e
2 changed files with 18 additions and 11 deletions

View file

@ -4,18 +4,8 @@
#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.
*/
@ -58,5 +48,5 @@ void __lockfunc tty_unlock_slave(struct tty_struct *tty)
void tty_set_lock_subclass(struct tty_struct *tty)
{
lockdep_set_subclass(&tty->legacy_mutex, TTY_MUTEX_SLAVE);
lockdep_set_subclass(&tty->legacy_mutex, TTY_LOCK_SLAVE);
}