| 1 | #include <linux/tty.h> |
| 2 | #include <linux/module.h> |
| 3 | #include <linux/kallsyms.h> |
| 4 | #include <linux/semaphore.h> |
| 5 | #include <linux/sched.h> |
| 6 | |
| 7 | /* |
| 8 | * Nested tty locks are necessary for releasing pty pairs. |
| 9 | * The stable lock order is master pty first, then slave pty. |
| 10 | */ |
| 11 | |
| 12 | /* Legacy tty mutex glue */ |
| 13 | |
| 14 | enum { |
| 15 | TTY_MUTEX_NORMAL, |
| 16 | TTY_MUTEX_SLAVE, |
| 17 | }; |
| 18 | |
| 19 | /* |
| 20 | * Getting the big tty mutex. |
| 21 | */ |
| 22 | |
| 23 | void __lockfunc tty_lock(struct tty_struct *tty) |
| 24 | { |
| 25 | if (tty->magic != TTY_MAGIC) { |
| 26 | pr_err("L Bad %p\n", tty); |
| 27 | WARN_ON(1); |
| 28 | return; |
| 29 | } |
| 30 | tty_kref_get(tty); |
| 31 | mutex_lock(&tty->legacy_mutex); |
| 32 | } |
| 33 | EXPORT_SYMBOL(tty_lock); |
| 34 | |
| 35 | void __lockfunc tty_unlock(struct tty_struct *tty) |
| 36 | { |
| 37 | if (tty->magic != TTY_MAGIC) { |
| 38 | pr_err("U Bad %p\n", tty); |
| 39 | WARN_ON(1); |
| 40 | return; |
| 41 | } |
| 42 | mutex_unlock(&tty->legacy_mutex); |
| 43 | tty_kref_put(tty); |
| 44 | } |
| 45 | EXPORT_SYMBOL(tty_unlock); |
| 46 | |
| 47 | void __lockfunc tty_lock_slave(struct tty_struct *tty) |
| 48 | { |
| 49 | if (tty && tty != tty->link) { |
| 50 | WARN_ON(!mutex_is_locked(&tty->link->legacy_mutex) || |
| 51 | !tty->driver->type == TTY_DRIVER_TYPE_PTY || |
| 52 | !tty->driver->type == PTY_TYPE_SLAVE); |
| 53 | tty_lock(tty); |
| 54 | } |
| 55 | } |
| 56 | |
| 57 | void __lockfunc tty_unlock_slave(struct tty_struct *tty) |
| 58 | { |
| 59 | if (tty && tty != tty->link) |
| 60 | tty_unlock(tty); |
| 61 | } |
| 62 | |
| 63 | void tty_set_lock_subclass(struct tty_struct *tty) |
| 64 | { |
| 65 | lockdep_set_subclass(&tty->legacy_mutex, TTY_MUTEX_SLAVE); |
| 66 | } |