Root/drivers/tty/tty_mutex.c

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/* Legacy tty mutex glue */
8
9enum {
10    TTY_MUTEX_NORMAL,
11    TTY_MUTEX_NESTED,
12};
13
14/*
15 * Getting the big tty mutex.
16 */
17
18static void __lockfunc tty_lock_nested(struct tty_struct *tty,
19                       unsigned int subclass)
20{
21    if (tty->magic != TTY_MAGIC) {
22        pr_err("L Bad %p\n", tty);
23        WARN_ON(1);
24        return;
25    }
26    tty_kref_get(tty);
27    mutex_lock_nested(&tty->legacy_mutex, subclass);
28}
29
30void __lockfunc tty_lock(struct tty_struct *tty)
31{
32    return tty_lock_nested(tty, TTY_MUTEX_NORMAL);
33}
34EXPORT_SYMBOL(tty_lock);
35
36void __lockfunc tty_unlock(struct tty_struct *tty)
37{
38    if (tty->magic != TTY_MAGIC) {
39        pr_err("U Bad %p\n", tty);
40        WARN_ON(1);
41        return;
42    }
43    mutex_unlock(&tty->legacy_mutex);
44    tty_kref_put(tty);
45}
46EXPORT_SYMBOL(tty_unlock);
47
48/*
49 * Getting the big tty mutex for a pair of ttys with lock ordering
50 * On a non pty/tty pair tty2 can be NULL which is just fine.
51 */
52void __lockfunc tty_lock_pair(struct tty_struct *tty,
53                    struct tty_struct *tty2)
54{
55    if (tty < tty2) {
56        tty_lock(tty);
57        tty_lock_nested(tty2, TTY_MUTEX_NESTED);
58    } else {
59        if (tty2 && tty2 != tty)
60            tty_lock(tty2);
61        tty_lock_nested(tty, TTY_MUTEX_NESTED);
62    }
63}
64EXPORT_SYMBOL(tty_lock_pair);
65
66void __lockfunc tty_unlock_pair(struct tty_struct *tty,
67                        struct tty_struct *tty2)
68{
69    tty_unlock(tty);
70    if (tty2 && tty2 != tty)
71        tty_unlock(tty2);
72}
73EXPORT_SYMBOL(tty_unlock_pair);
74

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