LXR linux/drivers/tty/tty

   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
  14enum {
  15        TTY_MUTEX_NORMAL,
  16        TTY_MUTEX_SLAVE,
  17};
  18
  19/*
  20 * Getting the big tty mutex.
  21 */
  22
  23void __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}
  33EXPORT_SYMBOL(tty_lock);
  34
  35int tty_lock_interruptible(struct tty_struct *tty)
  36{
  37        int ret;
  38
  39        if (WARN(tty->magic != TTY_MAGIC, "L Bad %p\n", tty))
  40                return -EIO;
  41        tty_kref_get(tty);
  42        ret = mutex_lock_interruptible(&tty->legacy_mutex);
  43        if (ret)
  44                tty_kref_put(tty);
  45        return ret;
  46}
  47
  48void __lockfunc tty_unlock(struct tty_struct *tty)
  49{
  50        if (tty->magic != TTY_MAGIC) {
  51                pr_err("U Bad %p\n", tty);
  52                WARN_ON(1);
  53                return;
  54        }
  55        mutex_unlock(&tty->legacy_mutex);
  56        tty_kref_put(tty);
  57}
  58EXPORT_SYMBOL(tty_unlock);
  59
  60void __lockfunc tty_lock_slave(struct tty_struct *tty)
  61{
  62        if (tty && tty != tty->link)
  63                tty_lock(tty);
  64}
  65
  66void __lockfunc tty_unlock_slave(struct tty_struct *tty)
  67{
  68        if (tty && tty != tty->link)
  69                tty_unlock(tty);
  70}
  71
  72void tty_set_lock_subclass(struct tty_struct *tty)
  73{
  74        lockdep_set_subclass(&tty->legacy_mutex, TTY_MUTEX_SLAVE);
  75}
  76