1 /* 2 * drivers/char/tty_lock.c 3 */ 4 #include <linux/tty.h> 5 #include <linux/module.h> 6 #include <linux/kallsyms.h> 7 #include <linux/semaphore.h> 8 #include <linux/sched.h> 9 10 /* 11 * The 'big tty mutex' 12 * 13 * This mutex is taken and released by tty_lock() and tty_unlock(), 14 * replacing the older big kernel lock. 15 * It can no longer be taken recursively, and does not get 16 * released implicitly while sleeping. 17 * 18 * Don't use in new code. 19 */ 20 static DEFINE_MUTEX(big_tty_mutex); 21 struct task_struct *__big_tty_mutex_owner; 22 EXPORT_SYMBOL_GPL(__big_tty_mutex_owner); 23 24 /* 25 * Getting the big tty mutex. 26 */ 27 void __lockfunc tty_lock(void) 28 { 29 struct task_struct *task = current; 30 31 WARN_ON(__big_tty_mutex_owner == task); 32 33 mutex_lock(&big_tty_mutex); 34 __big_tty_mutex_owner = task; 35 } 36 EXPORT_SYMBOL(tty_lock); 37 38 void __lockfunc tty_unlock(void) 39 { 40 struct task_struct *task = current; 41 42 WARN_ON(__big_tty_mutex_owner != task); 43 __big_tty_mutex_owner = NULL; 44 45 mutex_unlock(&big_tty_mutex); 46 } 47 EXPORT_SYMBOL(tty_unlock); 48