Release 4.7 drivers/tty/tty_ldisc.c

#include <linux/types.h>
#include <linux/errno.h>
#include <linux/kmod.h>
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/file.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/poll.h>
#include <linux/proc_fs.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/wait.h>
#include <linux/bitops.h>
#include <linux/seq_file.h>
#include <linux/uaccess.h>
#include <linux/ratelimit.h>


#undef LDISC_DEBUG_HANGUP

#ifdef LDISC_DEBUG_HANGUP

#define tty_ldisc_debug(tty, f, args...)	tty_debug(tty, f, ##args)
#else

#define tty_ldisc_debug(tty, f, args...)
#endif

/* lockdep nested classes for tty->ldisc_sem */
enum {
	
LDISC_SEM_NORMAL,
	
LDISC_SEM_OTHER,
};


/*
 *      This guards the refcounted line discipline lists. The lock
 *      must be taken with irqs off because there are hangup path
 *      callers who will do ldisc lookups and cannot sleep.
 */

static DEFINE_RAW_SPINLOCK(tty_ldiscs_lock);
/* Line disc dispatch table */

static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS];

/**
 *      tty_register_ldisc      -       install a line discipline
 *      @disc: ldisc number
 *      @new_ldisc: pointer to the ldisc object
 *
 *      Installs a new line discipline into the kernel. The discipline
 *      is set up as unreferenced and then made available to the kernel
 *      from this point onwards.
 *
 *      Locking:
 *              takes tty_ldiscs_lock to guard against ldisc races
 */



int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc)
{
	unsigned long flags;
	int ret = 0;

	if (disc < N_TTY || disc >= NR_LDISCS)
		return -EINVAL;

	raw_spin_lock_irqsave(&tty_ldiscs_lock, flags);
	tty_ldiscs[disc] = new_ldisc;
	new_ldisc->num = disc;
	new_ldisc->refcount = 0;
	raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags);

	return ret;
}
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EXPORT_SYMBOL(tty_register_ldisc);

/**
 *      tty_unregister_ldisc    -       unload a line discipline
 *      @disc: ldisc number
 *      @new_ldisc: pointer to the ldisc object
 *
 *      Remove a line discipline from the kernel providing it is not
 *      currently in use.
 *
 *      Locking:
 *              takes tty_ldiscs_lock to guard against ldisc races
 */



int tty_unregister_ldisc(int disc)
{
	unsigned long flags;
	int ret = 0;

	if (disc < N_TTY || disc >= NR_LDISCS)
		return -EINVAL;

	raw_spin_lock_irqsave(&tty_ldiscs_lock, flags);
	if (tty_ldiscs[disc]->refcount)
		ret = -EBUSY;
	else
		tty_ldiscs[disc] = NULL;
	raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags);

	return ret;
}
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EXPORT_SYMBOL(tty_unregister_ldisc);



static struct tty_ldisc_ops *get_ldops(int disc)
{
	unsigned long flags;
	struct tty_ldisc_ops *ldops, *ret;

	raw_spin_lock_irqsave(&tty_ldiscs_lock, flags);
	ret = ERR_PTR(-EINVAL);
	ldops = tty_ldiscs[disc];
	if (ldops) {
		ret = ERR_PTR(-EAGAIN);
		if (try_module_get(ldops->owner)) {
			ldops->refcount++;
			ret = ldops;
		}
	}
	raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags);
	return ret;
}

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static void put_ldops(struct tty_ldisc_ops *ldops)
{
	unsigned long flags;

	raw_spin_lock_irqsave(&tty_ldiscs_lock, flags);
	ldops->refcount--;
	module_put(ldops->owner);
	raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags);
}

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/**
 *      tty_ldisc_get           -       take a reference to an ldisc
 *      @disc: ldisc number
 *
 *      Takes a reference to a line discipline. Deals with refcounts and
 *      module locking counts.
 *
 *      Returns: -EINVAL if the discipline index is not [N_TTY..NR_LDISCS] or
 *                       if the discipline is not registered
 *               -EAGAIN if request_module() failed to load or register the
 *                       the discipline
 *               -ENOMEM if allocation failure
 *
 *               Otherwise, returns a pointer to the discipline and bumps the
 *               ref count
 *
 *      Locking:
 *              takes tty_ldiscs_lock to guard against ldisc races
 */



static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc)
{
	struct tty_ldisc *ld;
	struct tty_ldisc_ops *ldops;

	if (disc < N_TTY || disc >= NR_LDISCS)
		return ERR_PTR(-EINVAL);

	/*
         * Get the ldisc ops - we may need to request them to be loaded
         * dynamically and try again.
         */
	ldops = get_ldops(disc);
	if (IS_ERR(ldops)) {
		request_module("tty-ldisc-%d", disc);
		ldops = get_ldops(disc);
		if (IS_ERR(ldops))
			return ERR_CAST(ldops);
	}

	ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL);
	if (ld == NULL) {
		put_ldops(ldops);
		return ERR_PTR(-ENOMEM);
	}

	ld->ops = ldops;
	ld->tty = tty;

	return ld;
}

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/**
 *      tty_ldisc_put           -       release the ldisc
 *
 *      Complement of tty_ldisc_get().
 */


static void tty_ldisc_put(struct tty_ldisc *ld)
{
	if (WARN_ON_ONCE(!ld))
		return;

	put_ldops(ld->ops);
	kfree(ld);
}

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static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos)
{
	return (*pos < NR_LDISCS) ? pos : NULL;
}

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static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos)
{
	(*pos)++;
	return (*pos < NR_LDISCS) ? pos : NULL;
}

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static void tty_ldiscs_seq_stop(struct seq_file *m, void *v)
{
}

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static int tty_ldiscs_seq_show(struct seq_file *m, void *v)
{
	int i = *(loff_t *)v;
	struct tty_ldisc_ops *ldops;

	ldops = get_ldops(i);
	if (IS_ERR(ldops))
		return 0;
	seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i);
	put_ldops(ldops);
	return 0;
}

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static const struct seq_operations tty_ldiscs_seq_ops = {
	.start	= tty_ldiscs_seq_start,
	.next	= tty_ldiscs_seq_next,
	.stop	= tty_ldiscs_seq_stop,
	.show	= tty_ldiscs_seq_show,
};



static int proc_tty_ldiscs_open(struct inode *inode, struct file *file)
{
	return seq_open(file, &tty_ldiscs_seq_ops);
}

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const struct file_operations tty_ldiscs_proc_fops = {
	.owner		= THIS_MODULE,
	.open		= proc_tty_ldiscs_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= seq_release,
};

/**
 *      tty_ldisc_ref_wait      -       wait for the tty ldisc
 *      @tty: tty device
 *
 *      Dereference the line discipline for the terminal and take a
 *      reference to it. If the line discipline is in flux then
 *      wait patiently until it changes.
 *
 *      Returns: NULL if the tty has been hungup and not re-opened with
 *               a new file descriptor, otherwise valid ldisc reference
 *
 *      Note: Must not be called from an IRQ/timer context. The caller
 *      must also be careful not to hold other locks that will deadlock
 *      against a discipline change, such as an existing ldisc reference
 *      (which we check for)
 *
 *      Note: a file_operations routine (read/poll/write) should use this
 *      function to wait for any ldisc lifetime events to finish.
 */



struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
{
	ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT);
	if (!tty->ldisc)
		ldsem_up_read(&tty->ldisc_sem);
	return tty->ldisc;
}
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EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);

/**
 *      tty_ldisc_ref           -       get the tty ldisc
 *      @tty: tty device
 *
 *      Dereference the line discipline for the terminal and take a
 *      reference to it. If the line discipline is in flux then
 *      return NULL. Can be called from IRQ and timer functions.
 */



struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty)
{
	struct tty_ldisc *ld = NULL;

	if (ldsem_down_read_trylock(&tty->ldisc_sem)) {
		ld = tty->ldisc;
		if (!ld)
			ldsem_up_read(&tty->ldisc_sem);
	}
	return ld;
}
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EXPORT_SYMBOL_GPL(tty_ldisc_ref);

/**
 *      tty_ldisc_deref         -       free a tty ldisc reference
 *      @ld: reference to free up
 *
 *      Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May
 *      be called in IRQ context.
 */



void tty_ldisc_deref(struct tty_ldisc *ld)
{
	ldsem_up_read(&ld->tty->ldisc_sem);
}
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EXPORT_SYMBOL_GPL(tty_ldisc_deref);



static inline int

__tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout)
{
	return ldsem_down_write(&tty->ldisc_sem, timeout);
}

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static inline int

__tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout)
{
	return ldsem_down_write_nested(&tty->ldisc_sem,
				       LDISC_SEM_OTHER, timeout);
}

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static inline void __tty_ldisc_unlock(struct tty_struct *tty)
{
	ldsem_up_write(&tty->ldisc_sem);
}

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static int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout)
{
	int ret;

	ret = __tty_ldisc_lock(tty, timeout);
	if (!ret)
		return -EBUSY;
	set_bit(TTY_LDISC_HALTED, &tty->flags);
	return 0;
}

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static void tty_ldisc_unlock(struct tty_struct *tty)
{
	clear_bit(TTY_LDISC_HALTED, &tty->flags);
	__tty_ldisc_unlock(tty);
}

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static int

tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2,
			    unsigned long timeout)
{
	int ret;

	if (tty < tty2) {
		ret = __tty_ldisc_lock(tty, timeout);
		if (ret) {
			ret = __tty_ldisc_lock_nested(tty2, timeout);
			if (!ret)
				__tty_ldisc_unlock(tty);
		}
	} else {
		/* if this is possible, it has lots of implications */
		WARN_ON_ONCE(tty == tty2);
		if (tty2 && tty != tty2) {
			ret = __tty_ldisc_lock(tty2, timeout);
			if (ret) {
				ret = __tty_ldisc_lock_nested(tty, timeout);
				if (!ret)
					__tty_ldisc_unlock(tty2);
			}
		} else
			ret = __tty_ldisc_lock(tty, timeout);
	}

	if (!ret)
		return -EBUSY;

	set_bit(TTY_LDISC_HALTED, &tty->flags);
	if (tty2)
		set_bit(TTY_LDISC_HALTED, &tty2->flags);
	return 0;
}

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static void tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2)
{
	tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT);
}

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static void tty_ldisc_unlock_pair(struct tty_struct *tty,
				  struct tty_struct *tty2)
{
	__tty_ldisc_unlock(tty);
	if (tty2)
		__tty_ldisc_unlock(tty2);
}

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/**
 *      tty_ldisc_flush -       flush line discipline queue
 *      @tty: tty
 *
 *      Flush the line discipline queue (if any) and the tty flip buffers
 *      for this tty.
 */



void tty_ldisc_flush(struct tty_struct *tty)
{
	struct tty_ldisc *ld = tty_ldisc_ref(tty);

	tty_buffer_flush(tty, ld);
	if (ld)
		tty_ldisc_deref(ld);
}
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EXPORT_SYMBOL_GPL(tty_ldisc_flush);

/**
 *      tty_set_termios_ldisc           -       set ldisc field
 *      @tty: tty structure
 *      @disc: line discipline number
 *
 *      This is probably overkill for real world processors but
 *      they are not on hot paths so a little discipline won't do
 *      any harm.
 *
 *      The line discipline-related tty_struct fields are reset to
 *      prevent the ldisc driver from re-using stale information for
 *      the new ldisc instance.
 *
 *      Locking: takes termios_rwsem
 */



static void tty_set_termios_ldisc(struct tty_struct *tty, int disc)
{
	down_write(&tty->termios_rwsem);
	tty->termios.c_line = disc;
	up_write(&tty->termios_rwsem);

	tty->disc_data = NULL;
	tty->receive_room = 0;
}

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/**
 *      tty_ldisc_open          -       open a line discipline
 *      @tty: tty we are opening the ldisc on
 *      @ld: discipline to open
 *
 *      A helper opening method. Also a convenient debugging and check
 *      point.
 *
 *      Locking: always called with BTM already held.
 */



static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
{
	WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags));
	if (ld->ops->open) {
		int ret;
                /* BTM here locks versus a hangup event */
		ret = ld->ops->open(tty);
		if (ret)
			clear_bit(TTY_LDISC_OPEN, &tty->flags);

		tty_ldisc_debug(tty, "%p: opened\n", ld);
		return ret;
	}
	return 0;
}

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/**
 *      tty_ldisc_close         -       close a line discipline
 *      @tty: tty we are opening the ldisc on
 *      @ld: discipline to close
 *
 *      A helper close method. Also a convenient debugging and check
 *      point.
 */



static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld)
{
	WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags));
	clear_bit(TTY_LDISC_OPEN, &tty->flags);
	if (ld->ops->close)
		ld->ops->close(tty);
	tty_ldisc_debug(tty, "%p: closed\n", ld);
}

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/**
 *      tty_ldisc_restore       -       helper for tty ldisc change
 *      @tty: tty to recover
 *      @old: previous ldisc
 *
 *      Restore the previous line discipline or N_TTY when a line discipline
 *      change fails due to an open error
 */



static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old)
{
	struct tty_ldisc *new_ldisc;
	int r;

	/* There is an outstanding reference here so this is safe */
	old = tty_ldisc_get(tty, old->ops->num);
	WARN_ON(IS_ERR(old));
	tty->ldisc = old;
	tty_set_termios_ldisc(tty, old->ops->num);
	if (tty_ldisc_open(tty, old) < 0) {
		tty_ldisc_put(old);
		/* This driver is always present */
		new_ldisc = tty_ldisc_get(tty, N_TTY);
		if (IS_ERR(new_ldisc))
			panic("n_tty: get");
		tty->ldisc = new_ldisc;
		tty_set_termios_ldisc(tty, N_TTY);
		r = tty_ldisc_open(tty, new_ldisc);
		if (r < 0)
			panic("Couldn't open N_TTY ldisc for "
			      "%s --- error %d.",
			      tty_name(tty), r);
	}
}

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/**
 *      tty_set_ldisc           -       set line discipline
 *      @tty: the terminal to set
 *      @ldisc: the line discipline
 *
 *      Set the discipline of a tty line. Must be called from a process
 *      context. The ldisc change logic has to protect itself against any
 *      overlapping ldisc change (including on the other end of pty pairs),
 *      the close of one side of a tty/pty pair, and eventually hangup.
 */



int tty_set_ldisc(struct tty_struct *tty, int disc)
{
	int retval;
	struct tty_ldisc *old_ldisc, *new_ldisc;

	new_ldisc = tty_ldisc_get(tty, disc);
	if (IS_ERR(new_ldisc))
		return PTR_ERR(new_ldisc);

	tty_lock(tty);
	retval = tty_ldisc_lock(tty, 5 * HZ);
	if (retval)
		goto err;

	if (!tty->ldisc) {
		retval = -EIO;
		goto out;
	}

	/* Check the no-op case */
	if (tty->ldisc->ops->num == disc)
		goto out;

	if (test_bit(TTY_HUPPED, &tty->flags)) {
		/* We were raced by hangup */
		retval = -EIO;
		goto out;
	}

	old_ldisc = tty->ldisc;

	/* Shutdown the old discipline. */
	tty_ldisc_close(tty, old_ldisc);

	/* Now set up the new line discipline. */
	tty->ldisc = new_ldisc;
	tty_set_termios_ldisc(tty, disc);

	retval = tty_ldisc_open(tty, new_ldisc);
	if (retval < 0) {
		/* Back to the old one or N_TTY if we can't */
		tty_ldisc_put(new_ldisc);
		tty_ldisc_restore(tty, old_ldisc);
	}

	if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc) {
		down_read(&tty->termios_rwsem);
		tty->ops->set_ldisc(tty);
		up_read(&tty->termios_rwsem);
	}

	/* At this point we hold a reference to the new ldisc and a
           reference to the old ldisc, or we hold two references to
           the old ldisc (if it was restored as part of error cleanup
           above). In either case, releasing a single reference from
           the old ldisc is correct. */
	new_ldisc = old_ldisc;
out:
	tty_ldisc_unlock(tty);

	/* Restart the work queue in case no characters kick it off. Safe if
           already running */
	tty_buffer_restart_work(tty->port);
err:
	tty_ldisc_put(new_ldisc);	/* drop the extra reference */
	tty_unlock(tty);
	return retval;
}

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alan cox
alan cox
161
60.07%
4
22.22%
peter hurley
peter hurley
105
39.18%
12
66.67%
jiri slaby
jiri slaby
1
0.37%
1
5.56%
arnd bergmann
arnd bergmann
1
0.37%
1
5.56%
Total
268
100.00%
18
100.00%

/**
 *      tty_ldisc_kill  -       teardown ldisc
 *      @tty: tty being released
 *
 *      Perform final close of the ldisc and reset tty->ldisc
 */


static void tty_ldisc_kill(struct tty_struct *tty)
{
	if (!tty->ldisc)
		return;
	/*
         * Now kill off the ldisc
         */
	tty_ldisc_close(tty, tty->ldisc);
	tty_ldisc_put(tty->ldisc);
	/* Force an oops if we mess this up */
	tty->ldisc = NULL;
}

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peter hurley
peter hurley
43
100.00%
1
100.00%
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43
100.00%
1
100.00%

/**
 *      tty_reset_termios       -       reset terminal state
 *      @tty: tty to reset
 *
 *      Restore a terminal to the driver default state.
 */



static void tty_reset_termios(struct tty_struct *tty)
{
	down_write(&tty->termios_rwsem);
	tty->termios = tty->driver->init_termios;
	tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios);
	tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios);
	up_write(&tty->termios_rwsem);
}


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alan cox
alan cox
61
93.85%
3
75.00%
peter hurley
peter hurley
4
6.15%
1
25.00%
Total
65
100.00%
4
100.00%

/**
 *      tty_ldisc_reinit        -       reinitialise the tty ldisc
 *      @tty: tty to reinit
 *      @disc: line discipline to reinitialize
 *
 *      Completely reinitialize the line discipline state, by closing the
 *      current instance, if there is one, and opening a new instance. If
 *      an error occurs opening the new non-N_TTY instance, the instance
 *      is dropped and tty->ldisc reset to NULL. The caller can then retry
 *      with N_TTY instead.
 *
 *      Returns 0 if successful, otherwise error code < 0
 */



int tty_ldisc_reinit(struct tty_struct *tty, int disc)
{
	struct tty_ldisc *ld;
	int retval;

	ld = tty_ldisc_get(tty, disc);
	if (IS_ERR(ld)) {
		BUG_ON(disc == N_TTY);
		return PTR_ERR(ld);
	}

	if (tty->ldisc) {
		tty_ldisc_close(tty, tty->ldisc);
		tty_ldisc_put(tty->ldisc);
	}

	/* switch the line discipline */
	tty->ldisc = ld;
	tty_set_termios_ldisc(tty, disc);
	retval = tty_ldisc_open(tty, tty->ldisc);
	if (retval) {
		if (!WARN_ON(disc == N_TTY)) {
			tty_ldisc_put(tty->ldisc);
			tty->ldisc = NULL;
		}
	}
	return retval;
}

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peter hurley
peter hurley
77
57.04%
3
42.86%
alan cox
alan cox
43
31.85%
3
42.86%
philippe retornaz
philippe retornaz
15
11.11%
1
14.29%
Total
135
100.00%
7
100.00%

/**
 *      tty_ldisc_hangup                -       hangup ldisc reset
 *      @tty: tty being hung up
 *
 *      Some tty devices reset their termios when they receive a hangup
 *      event. In that situation we must also switch back to N_TTY properly
 *      before we reset the termios data.
 *
 *      Locking: We can take the ldisc mutex as the rest of the code is
 *      careful to allow for this.
 *
 *      In the pty pair case this occurs in the close() path of the
 *      tty itself so we must be careful about locking rules.
 */



void tty_ldisc_hangup(struct tty_struct *tty, bool reinit)
{
	struct tty_ldisc *ld;

	tty_ldisc_debug(tty, "%p: hangup\n", tty->ldisc);

	ld = tty_ldisc_ref(tty);
	if (ld != NULL) {
		if (ld->ops->flush_buffer)
			ld->ops->flush_buffer(tty);
		tty_driver_flush_buffer(tty);
		if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) &&
		    ld->ops->write_wakeup)
			ld->ops->write_wakeup(tty);
		if (ld->ops->hangup)
			ld->ops->hangup(tty);
		tty_ldisc_deref(ld);
	}

	wake_up_interruptible_poll(&tty->write_wait, POLLOUT);
	wake_up_interruptible_poll(&tty->read_wait, POLLIN);

	/*
         * Shutdown the current line discipline, and reset it to
         * N_TTY if need be.
         *
         * Avoid racing set_ldisc or tty_ldisc_release
         */
	tty_ldisc_lock(tty, MAX_SCHEDULE_TIMEOUT);

	if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS)
		tty_reset_termios(tty);

	if (tty->ldisc) {
		if (reinit) {
			if (tty_ldisc_reinit(tty, tty->termios.c_line) < 0)
				tty_ldisc_reinit(tty, N_TTY);
		} else
			tty_ldisc_kill(tty);
	}
	tty_ldisc_unlock(tty);
}

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alan cox
alan cox
153
73.91%
4
36.36%
peter hurley
peter hurley
52
25.12%
6
54.55%
jiri slaby
jiri slaby
2
0.97%
1
9.09%
Total
207
100.00%
11
100.00%

/**
 *      tty_ldisc_setup                 -       open line discipline
 *      @tty: tty being shut down
 *      @o_tty: pair tty for pty/tty pairs
 *
 *      Called during the initial open of a tty/pty pair in order to set up the
 *      line disciplines and bind them to the tty. This has no locking issues
 *      as the device isn't yet active.
 */



int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty)
{
	int retval = tty_ldisc_open(tty, tty->ldisc);
	if (retval)
		return retval;

	if (o_tty) {
		retval = tty_ldisc_open(o_tty, o_tty->ldisc);
		if (retval) {
			tty_ldisc_close(tty, tty->ldisc);
			return retval;
		}
	}
	return 0;
}

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alan cox
alan cox
64
88.89%
2
66.67%
peter hurley
peter hurley
8
11.11%
1
33.33%
Total
72
100.00%
3
100.00%

/**
 *      tty_ldisc_release               -       release line discipline
 *      @tty: tty being shut down (or one end of pty pair)
 *
 *      Called during the final close of a tty or a pty pair in order to shut
 *      down the line discpline layer. On exit, each tty's ldisc is NULL.
 */



void tty_ldisc_release(struct tty_struct *tty)
{
	struct tty_struct *o_tty = tty->link;

	/*
         * Shutdown this line discipline. As this is the final close,
         * it does not race with the set_ldisc code path.
         */

	tty_ldisc_lock_pair(tty, o_tty);
	tty_ldisc_kill(tty);
	if (o_tty)
		tty_ldisc_kill(o_tty);
	tty_ldisc_unlock_pair(tty, o_tty);

	/* And the memory resources remaining (buffers, termios) will be
           disposed of when the kref hits zero */

	tty_ldisc_debug(tty, "released\n");
}

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alan cox
alan cox
31
55.36%
6
46.15%
peter hurley
peter hurley
25
44.64%
7
53.85%
Total
56
100.00%
13
100.00%

/**
 *      tty_ldisc_init          -       ldisc setup for new tty
 *      @tty: tty being allocated
 *
 *      Set up the line discipline objects for a newly allocated tty. Note that
 *      the tty structure is not completely set up when this call is made.
 */



void tty_ldisc_init(struct tty_struct *tty)
{
	struct tty_ldisc *ld = tty_ldisc_get(tty, N_TTY);
	if (IS_ERR(ld))
		panic("n_tty: init_tty");
	tty->ldisc = ld;
}

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alan cox
alan cox
35
87.50%
2
50.00%
peter hurley
peter hurley
5
12.50%
2
50.00%
Total
40
100.00%
4
100.00%

/**
 *      tty_ldisc_deinit        -       ldisc cleanup for new tty
 *      @tty: tty that was allocated recently
 *
 *      The tty structure must not becompletely set up (tty_ldisc_setup) when
 *      this call is made.
 */


void tty_ldisc_deinit(struct tty_struct *tty)
{
	if (tty->ldisc)
		tty_ldisc_put(tty->ldisc);
	tty->ldisc = NULL;
}
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jiri slaby
jiri slaby
19
65.52%
1
25.00%
peter hurley
peter hurley
10
34.48%
3
75.00%
Total
29
100.00%
4
100.00%

Overall Contributors
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alan cox
alan cox
1461
55.42%
13
20.31%
peter hurley
peter hurley
929
35.24%
37
57.81%
linus torvalds
linus torvalds
177
6.71%
4
6.25%
jiri slaby
jiri slaby
38
1.44%
5
7.81%
philippe retornaz
philippe retornaz
15
0.57%
1
1.56%
ivo sieben
ivo sieben
12
0.46%
2
3.12%
arnd bergmann
arnd bergmann
3
0.11%
1
1.56%
guillaume gomez
guillaume gomez
1
0.04%
1
1.56%
Total
2636
100.00%
64
100.00%
  
Directory: drivers/tty

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