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
   9 enum {
  10         TTY_MUTEX_NORMAL,
  11         TTY_MUTEX_NESTED,
  12 };
  13
  14 /*
  15  * Getting the big tty mutex.
  16  */
  17
  18 static 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
  30 void __lockfunc tty_lock(struct tty_struct *tty)
  31 {
  32         return tty_lock_nested(tty, TTY_MUTEX_NORMAL);
  33 }
  34 EXPORT_SYMBOL(tty_lock);
  35
  36 void __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 }
  46 EXPORT_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  */
  52 void __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 }
  64 EXPORT_SYMBOL(tty_lock_pair);
  65
  66 void __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 }
  73 EXPORT_SYMBOL(tty_unlock_pair);