1 #include <linux/types.h>
2 #include <linux/errno.h>
3 #include <linux/kmod.h>
4 #include <linux/sched.h>
5 #include <linux/interrupt.h>
7 #include <linux/tty_driver.h>
8 #include <linux/file.h>
10 #include <linux/string.h>
11 #include <linux/slab.h>
12 #include <linux/poll.h>
13 #include <linux/proc_fs.h>
14 #include <linux/init.h>
15 #include <linux/module.h>
16 #include <linux/device.h>
17 #include <linux/wait.h>
18 #include <linux/bitops.h>
19 #include <linux/seq_file.h>
20 #include <linux/uaccess.h>
21 #include <linux/ratelimit.h>
23 #undef LDISC_DEBUG_HANGUP
25 #ifdef LDISC_DEBUG_HANGUP
26 #define tty_ldisc_debug(tty, f, args...) ({ \
28 printk(KERN_DEBUG "%s: %s: " f, __func__, tty_name(tty, __b), ##args); \
31 #define tty_ldisc_debug(tty, f, args...)
35 * This guards the refcounted line discipline lists. The lock
36 * must be taken with irqs off because there are hangup path
37 * callers who will do ldisc lookups and cannot sleep.
40 static DEFINE_RAW_SPINLOCK(tty_ldisc_lock);
41 static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait);
42 /* Line disc dispatch table */
43 static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS];
46 * tty_register_ldisc - install a line discipline
48 * @new_ldisc: pointer to the ldisc object
50 * Installs a new line discipline into the kernel. The discipline
51 * is set up as unreferenced and then made available to the kernel
52 * from this point onwards.
55 * takes tty_ldisc_lock to guard against ldisc races
58 int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc)
63 if (disc < N_TTY || disc >= NR_LDISCS)
66 raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
67 tty_ldiscs[disc] = new_ldisc;
68 new_ldisc->num = disc;
69 new_ldisc->refcount = 0;
70 raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
74 EXPORT_SYMBOL(tty_register_ldisc);
77 * tty_unregister_ldisc - unload a line discipline
79 * @new_ldisc: pointer to the ldisc object
81 * Remove a line discipline from the kernel providing it is not
85 * takes tty_ldisc_lock to guard against ldisc races
88 int tty_unregister_ldisc(int disc)
93 if (disc < N_TTY || disc >= NR_LDISCS)
96 raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
97 if (tty_ldiscs[disc]->refcount)
100 tty_ldiscs[disc] = NULL;
101 raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
105 EXPORT_SYMBOL(tty_unregister_ldisc);
107 static struct tty_ldisc_ops *get_ldops(int disc)
110 struct tty_ldisc_ops *ldops, *ret;
112 raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
113 ret = ERR_PTR(-EINVAL);
114 ldops = tty_ldiscs[disc];
116 ret = ERR_PTR(-EAGAIN);
117 if (try_module_get(ldops->owner)) {
122 raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
126 static void put_ldops(struct tty_ldisc_ops *ldops)
130 raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
132 module_put(ldops->owner);
133 raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
137 * tty_ldisc_get - take a reference to an ldisc
138 * @disc: ldisc number
140 * Takes a reference to a line discipline. Deals with refcounts and
141 * module locking counts. Returns NULL if the discipline is not available.
142 * Returns a pointer to the discipline and bumps the ref count if it is
146 * takes tty_ldisc_lock to guard against ldisc races
149 static struct tty_ldisc *tty_ldisc_get(int disc)
151 struct tty_ldisc *ld;
152 struct tty_ldisc_ops *ldops;
154 if (disc < N_TTY || disc >= NR_LDISCS)
155 return ERR_PTR(-EINVAL);
158 * Get the ldisc ops - we may need to request them to be loaded
159 * dynamically and try again.
161 ldops = get_ldops(disc);
163 request_module("tty-ldisc-%d", disc);
164 ldops = get_ldops(disc);
166 return ERR_CAST(ldops);
169 ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL);
172 return ERR_PTR(-ENOMEM);
176 atomic_set(&ld->users, 1);
177 init_waitqueue_head(&ld->wq_idle);
183 * tty_ldisc_put - release the ldisc
185 * Complement of tty_ldisc_get().
187 static inline void tty_ldisc_put(struct tty_ldisc *ld)
191 if (WARN_ON_ONCE(!ld))
194 raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
196 /* unreleased reader reference(s) will cause this WARN */
197 WARN_ON(!atomic_dec_and_test(&ld->users));
200 module_put(ld->ops->owner);
202 raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
205 static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos)
207 return (*pos < NR_LDISCS) ? pos : NULL;
210 static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos)
213 return (*pos < NR_LDISCS) ? pos : NULL;
216 static void tty_ldiscs_seq_stop(struct seq_file *m, void *v)
220 static int tty_ldiscs_seq_show(struct seq_file *m, void *v)
222 int i = *(loff_t *)v;
223 struct tty_ldisc_ops *ldops;
225 ldops = get_ldops(i);
228 seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i);
233 static const struct seq_operations tty_ldiscs_seq_ops = {
234 .start = tty_ldiscs_seq_start,
235 .next = tty_ldiscs_seq_next,
236 .stop = tty_ldiscs_seq_stop,
237 .show = tty_ldiscs_seq_show,
240 static int proc_tty_ldiscs_open(struct inode *inode, struct file *file)
242 return seq_open(file, &tty_ldiscs_seq_ops);
245 const struct file_operations tty_ldiscs_proc_fops = {
246 .owner = THIS_MODULE,
247 .open = proc_tty_ldiscs_open,
250 .release = seq_release,
254 * tty_ldisc_try - internal helper
257 * Make a single attempt to grab and bump the refcount on
258 * the tty ldisc. Return 0 on failure or 1 on success. This is
259 * used to implement both the waiting and non waiting versions
262 * Locking: takes tty_ldisc_lock
265 static struct tty_ldisc *tty_ldisc_try(struct tty_struct *tty)
268 struct tty_ldisc *ld;
270 /* FIXME: this allows reference acquire after TTY_LDISC is cleared */
271 raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
273 if (test_bit(TTY_LDISC, &tty->flags) && tty->ldisc) {
275 atomic_inc(&ld->users);
277 raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
282 * tty_ldisc_ref_wait - wait for the tty ldisc
285 * Dereference the line discipline for the terminal and take a
286 * reference to it. If the line discipline is in flux then
287 * wait patiently until it changes.
289 * Note: Must not be called from an IRQ/timer context. The caller
290 * must also be careful not to hold other locks that will deadlock
291 * against a discipline change, such as an existing ldisc reference
292 * (which we check for)
294 * Locking: call functions take tty_ldisc_lock
297 struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
299 struct tty_ldisc *ld;
301 /* wait_event is a macro */
302 wait_event(tty_ldisc_wait, (ld = tty_ldisc_try(tty)) != NULL);
305 EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);
308 * tty_ldisc_ref - get the tty ldisc
311 * Dereference the line discipline for the terminal and take a
312 * reference to it. If the line discipline is in flux then
313 * return NULL. Can be called from IRQ and timer functions.
315 * Locking: called functions take tty_ldisc_lock
318 struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty)
320 return tty_ldisc_try(tty);
322 EXPORT_SYMBOL_GPL(tty_ldisc_ref);
325 * tty_ldisc_deref - free a tty ldisc reference
326 * @ld: reference to free up
328 * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May
329 * be called in IRQ context.
331 * Locking: takes tty_ldisc_lock
334 void tty_ldisc_deref(struct tty_ldisc *ld)
338 if (WARN_ON_ONCE(!ld))
341 raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
343 * WARNs if one-too-many reader references were released
344 * - the last reference must be released with tty_ldisc_put
346 WARN_ON(atomic_dec_and_test(&ld->users));
347 raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
349 if (waitqueue_active(&ld->wq_idle))
350 wake_up(&ld->wq_idle);
352 EXPORT_SYMBOL_GPL(tty_ldisc_deref);
355 * tty_ldisc_enable - allow ldisc use
356 * @tty: terminal to activate ldisc on
358 * Set the TTY_LDISC flag when the line discipline can be called
359 * again. Do necessary wakeups for existing sleepers. Clear the LDISC
360 * changing flag to indicate any ldisc change is now over.
362 * Note: nobody should set the TTY_LDISC bit except via this function.
363 * Clearing directly is allowed.
366 static void tty_ldisc_enable(struct tty_struct *tty)
368 clear_bit(TTY_LDISC_HALTED, &tty->flags);
369 set_bit(TTY_LDISC, &tty->flags);
370 clear_bit(TTY_LDISC_CHANGING, &tty->flags);
371 wake_up(&tty_ldisc_wait);
375 * tty_ldisc_flush - flush line discipline queue
378 * Flush the line discipline queue (if any) for this tty. If there
379 * is no line discipline active this is a no-op.
382 void tty_ldisc_flush(struct tty_struct *tty)
384 struct tty_ldisc *ld = tty_ldisc_ref(tty);
386 if (ld->ops->flush_buffer)
387 ld->ops->flush_buffer(tty);
390 tty_buffer_flush(tty);
392 EXPORT_SYMBOL_GPL(tty_ldisc_flush);
395 * tty_set_termios_ldisc - set ldisc field
396 * @tty: tty structure
397 * @num: line discipline number
399 * This is probably overkill for real world processors but
400 * they are not on hot paths so a little discipline won't do
403 * Locking: takes termios_mutex
406 static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
408 mutex_lock(&tty->termios_mutex);
409 tty->termios.c_line = num;
410 mutex_unlock(&tty->termios_mutex);
414 * tty_ldisc_open - open a line discipline
415 * @tty: tty we are opening the ldisc on
416 * @ld: discipline to open
418 * A helper opening method. Also a convenient debugging and check
421 * Locking: always called with BTM already held.
424 static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
426 WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags));
429 /* BTM here locks versus a hangup event */
430 ret = ld->ops->open(tty);
432 clear_bit(TTY_LDISC_OPEN, &tty->flags);
439 * tty_ldisc_close - close a line discipline
440 * @tty: tty we are opening the ldisc on
441 * @ld: discipline to close
443 * A helper close method. Also a convenient debugging and check
447 static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld)
449 WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags));
450 clear_bit(TTY_LDISC_OPEN, &tty->flags);
456 * tty_ldisc_restore - helper for tty ldisc change
457 * @tty: tty to recover
458 * @old: previous ldisc
460 * Restore the previous line discipline or N_TTY when a line discipline
461 * change fails due to an open error
464 static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old)
467 struct tty_ldisc *new_ldisc;
470 /* There is an outstanding reference here so this is safe */
471 old = tty_ldisc_get(old->ops->num);
472 WARN_ON(IS_ERR(old));
474 tty_set_termios_ldisc(tty, old->ops->num);
475 if (tty_ldisc_open(tty, old) < 0) {
477 /* This driver is always present */
478 new_ldisc = tty_ldisc_get(N_TTY);
479 if (IS_ERR(new_ldisc))
481 tty->ldisc = new_ldisc;
482 tty_set_termios_ldisc(tty, N_TTY);
483 r = tty_ldisc_open(tty, new_ldisc);
485 panic("Couldn't open N_TTY ldisc for "
487 tty_name(tty, buf), r);
492 * tty_ldisc_wait_idle - wait for the ldisc to become idle
493 * @tty: tty to wait for
494 * @timeout: for how long to wait at most
496 * Wait for the line discipline to become idle. The discipline must
497 * have been halted for this to guarantee it remains idle.
499 static int tty_ldisc_wait_idle(struct tty_struct *tty, long timeout)
502 ret = wait_event_timeout(tty->ldisc->wq_idle,
503 atomic_read(&tty->ldisc->users) == 1, timeout);
504 return ret > 0 ? 0 : -EBUSY;
508 * tty_ldisc_halt - shut down the line discipline
510 * @o_tty: paired pty device (can be NULL)
511 * @timeout: # of jiffies to wait for ldisc refs to be released
513 * Shut down the line discipline and work queue for this tty device and
514 * its paired pty (if exists). Clearing the TTY_LDISC flag ensures
515 * no further references can be obtained, while waiting for existing
516 * references to be released ensures no more data is fed to the ldisc.
518 * You need to do a 'flush_scheduled_work()' (outside the ldisc_mutex)
519 * in order to make sure any currently executing ldisc work is also
523 static int tty_ldisc_halt(struct tty_struct *tty, struct tty_struct *o_tty,
528 clear_bit(TTY_LDISC, &tty->flags);
530 clear_bit(TTY_LDISC, &o_tty->flags);
532 retval = tty_ldisc_wait_idle(tty, timeout);
533 if (!retval && o_tty)
534 retval = tty_ldisc_wait_idle(o_tty, timeout);
538 set_bit(TTY_LDISC_HALTED, &tty->flags);
540 set_bit(TTY_LDISC_HALTED, &o_tty->flags);
546 * tty_ldisc_hangup_halt - halt the line discipline for hangup
547 * @tty: tty being hung up
549 * Shut down the line discipline and work queue for the tty device
550 * being hungup. Clear the TTY_LDISC flag to ensure no further
551 * references can be obtained and wait for remaining references to be
552 * released to ensure no more data is fed to this ldisc.
553 * Caller must hold legacy and ->ldisc_mutex.
555 * NB: tty_set_ldisc() is prevented from changing the ldisc concurrently
556 * with this function by checking the TTY_HUPPING flag.
558 static bool tty_ldisc_hangup_halt(struct tty_struct *tty)
560 char cur_n[TASK_COMM_LEN], tty_n[64];
561 long timeout = 3 * HZ;
563 clear_bit(TTY_LDISC, &tty->flags);
565 if (tty->ldisc) { /* Not yet closed */
568 while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) {
569 timeout = MAX_SCHEDULE_TIMEOUT;
570 printk_ratelimited(KERN_WARNING
571 "%s: waiting (%s) for %s took too long, but we keep waiting...\n",
572 __func__, get_task_comm(cur_n, current),
573 tty_name(tty, tty_n));
576 set_bit(TTY_LDISC_HALTED, &tty->flags);
578 /* must reacquire both locks and preserve lock order */
579 mutex_unlock(&tty->ldisc_mutex);
581 mutex_lock(&tty->ldisc_mutex);
587 * tty_set_ldisc - set line discipline
588 * @tty: the terminal to set
589 * @ldisc: the line discipline
591 * Set the discipline of a tty line. Must be called from a process
592 * context. The ldisc change logic has to protect itself against any
593 * overlapping ldisc change (including on the other end of pty pairs),
594 * the close of one side of a tty/pty pair, and eventually hangup.
596 * Locking: takes tty_ldisc_lock, termios_mutex
599 int tty_set_ldisc(struct tty_struct *tty, int ldisc)
602 struct tty_ldisc *o_ldisc, *new_ldisc;
603 struct tty_struct *o_tty;
605 new_ldisc = tty_ldisc_get(ldisc);
606 if (IS_ERR(new_ldisc))
607 return PTR_ERR(new_ldisc);
611 * We need to look at the tty locking here for pty/tty pairs
612 * when both sides try to change in parallel.
615 o_tty = tty->link; /* o_tty is the pty side or NULL */
619 * Check the no-op case
622 if (tty->ldisc->ops->num == ldisc) {
624 tty_ldisc_put(new_ldisc);
630 * Problem: What do we do if this blocks ?
631 * We could deadlock here
634 tty_wait_until_sent(tty, 0);
637 mutex_lock(&tty->ldisc_mutex);
640 * We could be midstream of another ldisc change which has
641 * dropped the lock during processing. If so we need to wait.
644 while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) {
645 mutex_unlock(&tty->ldisc_mutex);
647 wait_event(tty_ldisc_wait,
648 test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0);
650 mutex_lock(&tty->ldisc_mutex);
653 set_bit(TTY_LDISC_CHANGING, &tty->flags);
656 * No more input please, we are switching. The new ldisc
657 * will update this value in the ldisc open function
660 tty->receive_room = 0;
662 o_ldisc = tty->ldisc;
666 * Make sure we don't change while someone holds a
667 * reference to the line discipline. The TTY_LDISC bit
668 * prevents anyone taking a reference once it is clear.
669 * We need the lock to avoid racing reference takers.
671 * We must clear the TTY_LDISC bit here to avoid a livelock
672 * with a userspace app continually trying to use the tty in
673 * parallel to the change and re-referencing the tty.
676 retval = tty_ldisc_halt(tty, o_tty, 5 * HZ);
679 * Wait for hangup to complete, if pending.
680 * We must drop the mutex here in case a hangup is also in process.
683 mutex_unlock(&tty->ldisc_mutex);
685 flush_work(&tty->hangup_work);
688 mutex_lock(&tty->ldisc_mutex);
690 /* handle wait idle failure locked */
692 tty_ldisc_put(new_ldisc);
696 if (test_bit(TTY_HUPPING, &tty->flags)) {
697 /* We were raced by the hangup method. It will have stomped
698 the ldisc data and closed the ldisc down */
699 clear_bit(TTY_LDISC_CHANGING, &tty->flags);
700 mutex_unlock(&tty->ldisc_mutex);
701 tty_ldisc_put(new_ldisc);
706 /* Shutdown the current discipline. */
707 tty_ldisc_close(tty, o_ldisc);
709 /* Now set up the new line discipline. */
710 tty->ldisc = new_ldisc;
711 tty_set_termios_ldisc(tty, ldisc);
713 retval = tty_ldisc_open(tty, new_ldisc);
715 /* Back to the old one or N_TTY if we can't */
716 tty_ldisc_put(new_ldisc);
717 tty_ldisc_restore(tty, o_ldisc);
720 /* At this point we hold a reference to the new ldisc and a
721 a reference to the old ldisc. If we ended up flipping back
722 to the existing ldisc we have two references to it */
724 if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc)
725 tty->ops->set_ldisc(tty);
727 tty_ldisc_put(o_ldisc);
731 * Allow ldisc referencing to occur again
734 tty_ldisc_enable(tty);
736 tty_ldisc_enable(o_tty);
738 /* Restart the work queue in case no characters kick it off. Safe if
740 schedule_work(&tty->port->buf.work);
742 schedule_work(&o_tty->port->buf.work);
744 mutex_unlock(&tty->ldisc_mutex);
750 * tty_reset_termios - reset terminal state
753 * Restore a terminal to the driver default state.
756 static void tty_reset_termios(struct tty_struct *tty)
758 mutex_lock(&tty->termios_mutex);
759 tty->termios = tty->driver->init_termios;
760 tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios);
761 tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios);
762 mutex_unlock(&tty->termios_mutex);
767 * tty_ldisc_reinit - reinitialise the tty ldisc
768 * @tty: tty to reinit
769 * @ldisc: line discipline to reinitialize
771 * Switch the tty to a line discipline and leave the ldisc
775 static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc)
777 struct tty_ldisc *ld = tty_ldisc_get(ldisc);
782 tty_ldisc_close(tty, tty->ldisc);
783 tty_ldisc_put(tty->ldisc);
785 * Switch the line discipline back
788 tty_set_termios_ldisc(tty, ldisc);
794 * tty_ldisc_hangup - hangup ldisc reset
795 * @tty: tty being hung up
797 * Some tty devices reset their termios when they receive a hangup
798 * event. In that situation we must also switch back to N_TTY properly
799 * before we reset the termios data.
801 * Locking: We can take the ldisc mutex as the rest of the code is
802 * careful to allow for this.
804 * In the pty pair case this occurs in the close() path of the
805 * tty itself so we must be careful about locking rules.
808 void tty_ldisc_hangup(struct tty_struct *tty)
810 struct tty_ldisc *ld;
811 int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS;
814 tty_ldisc_debug(tty, "closing ldisc: %p\n", tty->ldisc);
817 * FIXME! What are the locking issues here? This may me overdoing
818 * things... This question is especially important now that we've
819 * removed the irqlock.
821 ld = tty_ldisc_ref(tty);
823 /* We may have no line discipline at this point */
824 if (ld->ops->flush_buffer)
825 ld->ops->flush_buffer(tty);
826 tty_driver_flush_buffer(tty);
827 if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) &&
828 ld->ops->write_wakeup)
829 ld->ops->write_wakeup(tty);
831 ld->ops->hangup(tty);
835 * FIXME: Once we trust the LDISC code better we can wait here for
836 * ldisc completion and fix the driver call race
838 wake_up_interruptible_poll(&tty->write_wait, POLLOUT);
839 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
841 * Shutdown the current line discipline, and reset it to
844 * Avoid racing set_ldisc or tty_ldisc_release
846 mutex_lock(&tty->ldisc_mutex);
848 if (tty_ldisc_hangup_halt(tty)) {
850 /* At this point we have a halted ldisc; we want to close it and
851 reopen a new ldisc. We could defer the reopen to the next
852 open but it means auditing a lot of other paths so this is
856 if (!tty_ldisc_reinit(tty, tty->termios.c_line))
857 err = tty_ldisc_open(tty, tty->ldisc);
861 /* If the re-open fails or we reset then go to N_TTY. The
862 N_TTY open cannot fail */
864 BUG_ON(tty_ldisc_reinit(tty, N_TTY));
865 WARN_ON(tty_ldisc_open(tty, tty->ldisc));
867 tty_ldisc_enable(tty);
869 mutex_unlock(&tty->ldisc_mutex);
871 tty_reset_termios(tty);
873 tty_ldisc_debug(tty, "re-opened ldisc: %p\n", tty->ldisc);
877 * tty_ldisc_setup - open line discipline
878 * @tty: tty being shut down
879 * @o_tty: pair tty for pty/tty pairs
881 * Called during the initial open of a tty/pty pair in order to set up the
882 * line disciplines and bind them to the tty. This has no locking issues
883 * as the device isn't yet active.
886 int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty)
888 struct tty_ldisc *ld = tty->ldisc;
891 retval = tty_ldisc_open(tty, ld);
896 retval = tty_ldisc_open(o_tty, o_tty->ldisc);
898 tty_ldisc_close(tty, ld);
901 tty_ldisc_enable(o_tty);
903 tty_ldisc_enable(tty);
907 static void tty_ldisc_kill(struct tty_struct *tty)
909 mutex_lock(&tty->ldisc_mutex);
911 * Now kill off the ldisc
913 tty_ldisc_close(tty, tty->ldisc);
914 tty_ldisc_put(tty->ldisc);
915 /* Force an oops if we mess this up */
918 /* Ensure the next open requests the N_TTY ldisc */
919 tty_set_termios_ldisc(tty, N_TTY);
920 mutex_unlock(&tty->ldisc_mutex);
924 * tty_ldisc_release - release line discipline
925 * @tty: tty being shut down
926 * @o_tty: pair tty for pty/tty pairs
928 * Called during the final close of a tty/pty pair in order to shut down
929 * the line discpline layer. On exit the ldisc assigned is N_TTY and the
930 * ldisc has not been opened.
933 void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
936 * Shutdown this line discipline. As this is the final close,
937 * it does not race with the set_ldisc code path.
940 tty_ldisc_debug(tty, "closing ldisc: %p\n", tty->ldisc);
942 tty_ldisc_halt(tty, o_tty, MAX_SCHEDULE_TIMEOUT);
944 tty_lock_pair(tty, o_tty);
945 /* This will need doing differently if we need to lock */
948 tty_ldisc_kill(o_tty);
950 tty_unlock_pair(tty, o_tty);
951 /* And the memory resources remaining (buffers, termios) will be
952 disposed of when the kref hits zero */
954 tty_ldisc_debug(tty, "ldisc closed\n");
958 * tty_ldisc_init - ldisc setup for new tty
959 * @tty: tty being allocated
961 * Set up the line discipline objects for a newly allocated tty. Note that
962 * the tty structure is not completely set up when this call is made.
965 void tty_ldisc_init(struct tty_struct *tty)
967 struct tty_ldisc *ld = tty_ldisc_get(N_TTY);
969 panic("n_tty: init_tty");
974 * tty_ldisc_init - ldisc cleanup for new tty
975 * @tty: tty that was allocated recently
977 * The tty structure must not becompletely set up (tty_ldisc_setup) when
980 void tty_ldisc_deinit(struct tty_struct *tty)
982 tty_ldisc_put(tty->ldisc);
986 void tty_ldisc_begin(void)
988 /* Setup the default TTY line discipline. */
989 (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY);