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 /*
   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 }