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 */ 20static DEFINE_MUTEX(big_tty_mutex); 21struct task_struct *__big_tty_mutex_owner; 22EXPORT_SYMBOL_GPL(__big_tty_mutex_owner); 23 24/* 25 * Getting the big tty mutex. 26 */ 27void __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} 36EXPORT_SYMBOL(tty_lock); 37 38void __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} 47EXPORT_SYMBOL(tty_unlock); 48