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  * The 'big tty mutex'
   9  *
  10  * This mutex is taken and released by tty_lock() and tty_unlock(),
  11  * replacing the older big kernel lock.
  12  * It can no longer be taken recursively, and does not get
  13  * released implicitly while sleeping.
  14  *
  15  * Don't use in new code.
  16  */
  17 static DEFINE_MUTEX(big_tty_mutex);
  18 struct task_struct *__big_tty_mutex_owner;
  19 EXPORT_SYMBOL_GPL(__big_tty_mutex_owner);
  20
  21 /*
  22  * Getting the big tty mutex.
  23  */
  24 void __lockfunc tty_lock(void)
  25 {
  26         struct task_struct *task = current;
  27
  28         WARN_ON(__big_tty_mutex_owner == task);
  29
  30         mutex_lock(&big_tty_mutex);
  31         __big_tty_mutex_owner = task;
  32 }
  33 EXPORT_SYMBOL(tty_lock);
  34
  35 void __lockfunc tty_unlock(void)
  36 {
  37         struct task_struct *task = current;
  38
  39         WARN_ON(__big_tty_mutex_owner != task);
  40         __big_tty_mutex_owner = NULL;
  41
  42         mutex_unlock(&big_tty_mutex);
  43 }
  44 EXPORT_SYMBOL(tty_unlock);