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_NESTED,
  17 };
  18
  19 /*
  20  * Getting the big tty mutex.
  21  */
  22
  23 static void __lockfunc tty_lock_nested(struct tty_struct *tty,
  24                                        unsigned int subclass)
  25 {
  26         if (tty->magic != TTY_MAGIC) {
  27                 pr_err("L Bad %p\n", tty);
  28                 WARN_ON(1);
  29                 return;
  30         }
  31         tty_kref_get(tty);
  32         mutex_lock_nested(&tty->legacy_mutex, subclass);
  33 }
  34
  35 void __lockfunc tty_lock(struct tty_struct *tty)
  36 {
  37         return tty_lock_nested(tty, TTY_MUTEX_NORMAL);
  38 }
  39 EXPORT_SYMBOL(tty_lock);
  40
  41 void __lockfunc tty_unlock(struct tty_struct *tty)
  42 {
  43         if (tty->magic != TTY_MAGIC) {
  44                 pr_err("U Bad %p\n", tty);
  45                 WARN_ON(1);
  46                 return;
  47         }
  48         mutex_unlock(&tty->legacy_mutex);
  49         tty_kref_put(tty);
  50 }
  51 EXPORT_SYMBOL(tty_unlock);
  52
  53 void __lockfunc tty_lock_slave(struct tty_struct *tty)
  54 {
  55         if (tty && tty != tty->link) {
  56                 WARN_ON(!mutex_is_locked(&tty->link->legacy_mutex) ||
  57                         !tty->driver->type == TTY_DRIVER_TYPE_PTY ||
  58                         !tty->driver->type == PTY_TYPE_SLAVE);
  59                 tty_lock_nested(tty, TTY_MUTEX_NESTED);
  60         }
  61 }
  62
  63 void __lockfunc tty_unlock_slave(struct tty_struct *tty)
  64 {
  65         if (tty && tty != tty->link)
  66                 tty_unlock(tty);
  67 }