tty_mutex.c
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/*
* drivers/char/tty_lock.c
*/
#include <linux/tty.h>
#include <linux/module.h>
#include <linux/kallsyms.h>
#include <linux/semaphore.h>
#include <linux/sched.h>
/*
* The 'big tty mutex'
*
* This mutex is taken and released by tty_lock() and tty_unlock(),
* replacing the older big kernel lock.
* It can no longer be taken recursively, and does not get
* released implicitly while sleeping.
*
* Don't use in new code.
*/
static DEFINE_MUTEX(big_tty_mutex);
struct task_struct *__big_tty_mutex_owner;
EXPORT_SYMBOL_GPL(__big_tty_mutex_owner);
/*
* Getting the big tty mutex.
*/
void __lockfunc tty_lock(void)
{
struct task_struct *task = current;
WARN_ON(__big_tty_mutex_owner == task);
mutex_lock(&big_tty_mutex);
__big_tty_mutex_owner = task;
}
EXPORT_SYMBOL(tty_lock);
void __lockfunc tty_unlock(void)
{
struct task_struct *task = current;
WARN_ON(__big_tty_mutex_owner != task);
__big_tty_mutex_owner = NULL;
mutex_unlock(&big_tty_mutex);
}
EXPORT_SYMBOL(tty_unlock);