2008-07-22 04:16:55 -06:00
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#include <linux/types.h>
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#include <linux/errno.h>
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2011-11-16 08:27:10 -07:00
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#include <linux/kmod.h>
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2008-07-22 04:16:55 -06:00
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#include <linux/sched.h>
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#include <linux/interrupt.h>
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#include <linux/tty.h>
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#include <linux/tty_driver.h>
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#include <linux/file.h>
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#include <linux/mm.h>
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#include <linux/string.h>
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#include <linux/slab.h>
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#include <linux/poll.h>
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#include <linux/proc_fs.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/device.h>
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#include <linux/wait.h>
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#include <linux/bitops.h>
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#include <linux/seq_file.h>
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#include <linux/uaccess.h>
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2011-11-16 08:27:09 -07:00
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#include <linux/ratelimit.h>
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2008-07-22 04:16:55 -06:00
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2013-03-11 14:44:38 -06:00
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#undef LDISC_DEBUG_HANGUP
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#ifdef LDISC_DEBUG_HANGUP
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#define tty_ldisc_debug(tty, f, args...) ({ \
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char __b[64]; \
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printk(KERN_DEBUG "%s: %s: " f, __func__, tty_name(tty, __b), ##args); \
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})
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#else
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#define tty_ldisc_debug(tty, f, args...)
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#endif
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2013-06-15 05:04:47 -06:00
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/* lockdep nested classes for tty->ldisc_sem */
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enum {
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LDISC_SEM_NORMAL,
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LDISC_SEM_OTHER,
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};
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2008-07-22 04:16:55 -06:00
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/*
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* This guards the refcounted line discipline lists. The lock
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* must be taken with irqs off because there are hangup path
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* callers who will do ldisc lookups and cannot sleep.
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*/
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2013-06-15 05:04:46 -06:00
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static DEFINE_RAW_SPINLOCK(tty_ldiscs_lock);
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2008-07-22 04:16:55 -06:00
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/* Line disc dispatch table */
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static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS];
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/**
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* tty_register_ldisc - install a line discipline
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* @disc: ldisc number
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* @new_ldisc: pointer to the ldisc object
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*
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* Installs a new line discipline into the kernel. The discipline
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* is set up as unreferenced and then made available to the kernel
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* from this point onwards.
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*
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* Locking:
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2013-06-15 05:04:46 -06:00
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* takes tty_ldiscs_lock to guard against ldisc races
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2008-07-22 04:16:55 -06:00
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*/
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int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc)
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{
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unsigned long flags;
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int ret = 0;
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if (disc < N_TTY || disc >= NR_LDISCS)
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return -EINVAL;
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2013-06-15 05:04:46 -06:00
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raw_spin_lock_irqsave(&tty_ldiscs_lock, flags);
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2008-07-22 04:16:55 -06:00
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tty_ldiscs[disc] = new_ldisc;
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new_ldisc->num = disc;
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new_ldisc->refcount = 0;
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2013-06-15 05:04:46 -06:00
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raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags);
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2008-07-22 04:16:55 -06:00
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return ret;
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}
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EXPORT_SYMBOL(tty_register_ldisc);
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/**
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* tty_unregister_ldisc - unload a line discipline
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* @disc: ldisc number
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* @new_ldisc: pointer to the ldisc object
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*
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* Remove a line discipline from the kernel providing it is not
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* currently in use.
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*
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* Locking:
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2013-06-15 05:04:46 -06:00
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* takes tty_ldiscs_lock to guard against ldisc races
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2008-07-22 04:16:55 -06:00
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*/
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int tty_unregister_ldisc(int disc)
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{
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unsigned long flags;
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int ret = 0;
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if (disc < N_TTY || disc >= NR_LDISCS)
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return -EINVAL;
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2013-06-15 05:04:46 -06:00
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raw_spin_lock_irqsave(&tty_ldiscs_lock, flags);
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2008-07-22 04:16:55 -06:00
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if (tty_ldiscs[disc]->refcount)
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ret = -EBUSY;
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else
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tty_ldiscs[disc] = NULL;
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2013-06-15 05:04:46 -06:00
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raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags);
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2008-07-22 04:16:55 -06:00
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return ret;
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}
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EXPORT_SYMBOL(tty_unregister_ldisc);
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2009-08-03 17:00:15 -06:00
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static struct tty_ldisc_ops *get_ldops(int disc)
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{
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unsigned long flags;
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struct tty_ldisc_ops *ldops, *ret;
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2013-06-15 05:04:46 -06:00
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raw_spin_lock_irqsave(&tty_ldiscs_lock, flags);
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2009-08-03 17:00:15 -06:00
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ret = ERR_PTR(-EINVAL);
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ldops = tty_ldiscs[disc];
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if (ldops) {
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ret = ERR_PTR(-EAGAIN);
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if (try_module_get(ldops->owner)) {
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ldops->refcount++;
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ret = ldops;
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}
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}
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2013-06-15 05:04:46 -06:00
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raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags);
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2009-08-03 17:00:15 -06:00
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return ret;
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}
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static void put_ldops(struct tty_ldisc_ops *ldops)
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{
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unsigned long flags;
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2013-06-15 05:04:46 -06:00
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raw_spin_lock_irqsave(&tty_ldiscs_lock, flags);
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2009-08-03 17:00:15 -06:00
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ldops->refcount--;
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module_put(ldops->owner);
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2013-06-15 05:04:46 -06:00
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raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags);
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2009-08-03 17:00:15 -06:00
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}
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2008-07-22 04:16:55 -06:00
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/**
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* tty_ldisc_get - take a reference to an ldisc
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* @disc: ldisc number
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*
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* Takes a reference to a line discipline. Deals with refcounts and
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* module locking counts. Returns NULL if the discipline is not available.
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* Returns a pointer to the discipline and bumps the ref count if it is
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* available
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*
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* Locking:
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2013-06-15 05:04:46 -06:00
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* takes tty_ldiscs_lock to guard against ldisc races
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2008-07-22 04:16:55 -06:00
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*/
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2013-06-15 05:04:48 -06:00
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static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc)
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2008-07-22 04:16:55 -06:00
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{
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2009-06-11 05:50:12 -06:00
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struct tty_ldisc *ld;
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2009-08-03 17:01:28 -06:00
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struct tty_ldisc_ops *ldops;
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2008-07-22 04:16:55 -06:00
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if (disc < N_TTY || disc >= NR_LDISCS)
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2009-06-11 05:50:12 -06:00
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return ERR_PTR(-EINVAL);
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2009-08-03 17:01:28 -06:00
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/*
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* Get the ldisc ops - we may need to request them to be loaded
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* dynamically and try again.
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*/
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ldops = get_ldops(disc);
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if (IS_ERR(ldops)) {
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2008-07-22 04:16:55 -06:00
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request_module("tty-ldisc-%d", disc);
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2009-08-03 17:01:28 -06:00
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ldops = get_ldops(disc);
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if (IS_ERR(ldops))
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return ERR_CAST(ldops);
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}
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ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL);
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if (ld == NULL) {
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put_ldops(ldops);
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return ERR_PTR(-ENOMEM);
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2008-07-22 04:16:55 -06:00
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}
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2009-08-03 17:01:28 -06:00
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ld->ops = ldops;
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2013-06-15 05:04:48 -06:00
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ld->tty = tty;
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2012-05-03 06:37:43 -06:00
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2009-06-11 05:50:12 -06:00
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return ld;
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2008-07-22 04:16:55 -06:00
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}
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2013-03-11 14:44:43 -06:00
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/**
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* tty_ldisc_put - release the ldisc
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*
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* Complement of tty_ldisc_get().
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*/
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static inline void tty_ldisc_put(struct tty_ldisc *ld)
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{
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if (WARN_ON_ONCE(!ld))
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return;
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2013-06-15 05:04:48 -06:00
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put_ldops(ld->ops);
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2013-03-11 14:44:43 -06:00
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kfree(ld);
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}
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2009-06-11 05:51:41 -06:00
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static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos)
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2008-07-22 04:16:55 -06:00
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{
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return (*pos < NR_LDISCS) ? pos : NULL;
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}
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2009-06-11 05:51:41 -06:00
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static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos)
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2008-07-22 04:16:55 -06:00
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{
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(*pos)++;
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return (*pos < NR_LDISCS) ? pos : NULL;
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}
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static void tty_ldiscs_seq_stop(struct seq_file *m, void *v)
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{
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}
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static int tty_ldiscs_seq_show(struct seq_file *m, void *v)
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{
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int i = *(loff_t *)v;
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2009-08-03 17:00:15 -06:00
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struct tty_ldisc_ops *ldops;
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2009-06-11 05:51:41 -06:00
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2009-08-03 17:00:15 -06:00
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ldops = get_ldops(i);
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if (IS_ERR(ldops))
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2008-07-22 04:16:55 -06:00
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return 0;
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2009-08-03 17:00:15 -06:00
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seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i);
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put_ldops(ldops);
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2008-07-22 04:16:55 -06:00
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return 0;
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}
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static const struct seq_operations tty_ldiscs_seq_ops = {
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.start = tty_ldiscs_seq_start,
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.next = tty_ldiscs_seq_next,
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.stop = tty_ldiscs_seq_stop,
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.show = tty_ldiscs_seq_show,
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};
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static int proc_tty_ldiscs_open(struct inode *inode, struct file *file)
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{
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return seq_open(file, &tty_ldiscs_seq_ops);
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}
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const struct file_operations tty_ldiscs_proc_fops = {
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.owner = THIS_MODULE,
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.open = proc_tty_ldiscs_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = seq_release,
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};
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/**
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* tty_ldisc_ref_wait - wait for the tty ldisc
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* @tty: tty device
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*
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* Dereference the line discipline for the terminal and take a
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* reference to it. If the line discipline is in flux then
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* wait patiently until it changes.
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*
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* Note: Must not be called from an IRQ/timer context. The caller
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* must also be careful not to hold other locks that will deadlock
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* against a discipline change, such as an existing ldisc reference
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* (which we check for)
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*
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2013-06-15 05:04:48 -06:00
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* Note: only callable from a file_operations routine (which
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* guarantees tty->ldisc != NULL when the lock is acquired).
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2008-07-22 04:16:55 -06:00
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*/
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struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
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{
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2013-06-15 05:04:48 -06:00
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ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT);
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WARN_ON(!tty->ldisc);
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return tty->ldisc;
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2008-07-22 04:16:55 -06:00
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}
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EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);
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/**
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* tty_ldisc_ref - get the tty ldisc
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* @tty: tty device
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*
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* Dereference the line discipline for the terminal and take a
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* reference to it. If the line discipline is in flux then
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* return NULL. Can be called from IRQ and timer functions.
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*/
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struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty)
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{
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2013-06-15 05:04:48 -06:00
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struct tty_ldisc *ld = NULL;
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if (ldsem_down_read_trylock(&tty->ldisc_sem)) {
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ld = tty->ldisc;
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if (!ld)
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ldsem_up_read(&tty->ldisc_sem);
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}
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return ld;
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2008-07-22 04:16:55 -06:00
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}
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EXPORT_SYMBOL_GPL(tty_ldisc_ref);
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/**
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* tty_ldisc_deref - free a tty ldisc reference
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* @ld: reference to free up
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*
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* Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May
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* be called in IRQ context.
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*/
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void tty_ldisc_deref(struct tty_ldisc *ld)
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{
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2013-06-15 05:04:48 -06:00
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ldsem_up_read(&ld->tty->ldisc_sem);
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2008-07-22 04:16:55 -06:00
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}
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EXPORT_SYMBOL_GPL(tty_ldisc_deref);
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2013-06-15 05:04:47 -06:00
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static inline int __lockfunc
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tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout)
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{
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return ldsem_down_write(&tty->ldisc_sem, timeout);
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}
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static inline int __lockfunc
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tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout)
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{
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return ldsem_down_write_nested(&tty->ldisc_sem,
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LDISC_SEM_OTHER, timeout);
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}
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static inline void tty_ldisc_unlock(struct tty_struct *tty)
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{
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return ldsem_up_write(&tty->ldisc_sem);
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}
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static int __lockfunc
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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;
|
|
|
|
}
|
|
|
|
|
|
|
|
static void __lockfunc
|
|
|
|
tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2)
|
|
|
|
{
|
|
|
|
tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT);
|
|
|
|
}
|
|
|
|
|
|
|
|
static void __lockfunc tty_ldisc_unlock_pair(struct tty_struct *tty,
|
|
|
|
struct tty_struct *tty2)
|
|
|
|
{
|
|
|
|
tty_ldisc_unlock(tty);
|
|
|
|
if (tty2)
|
|
|
|
tty_ldisc_unlock(tty2);
|
|
|
|
}
|
|
|
|
|
|
|
|
static void __lockfunc tty_ldisc_enable_pair(struct tty_struct *tty,
|
|
|
|
struct tty_struct *tty2)
|
|
|
|
{
|
|
|
|
clear_bit(TTY_LDISC_HALTED, &tty->flags);
|
|
|
|
if (tty2)
|
|
|
|
clear_bit(TTY_LDISC_HALTED, &tty2->flags);
|
|
|
|
|
|
|
|
tty_ldisc_unlock_pair(tty, tty2);
|
|
|
|
}
|
|
|
|
|
2009-06-11 05:50:58 -06:00
|
|
|
/**
|
|
|
|
* tty_ldisc_flush - flush line discipline queue
|
|
|
|
* @tty: tty
|
|
|
|
*
|
|
|
|
* Flush the line discipline queue (if any) for this tty. If there
|
|
|
|
* is no line discipline active this is a no-op.
|
|
|
|
*/
|
|
|
|
|
|
|
|
void tty_ldisc_flush(struct tty_struct *tty)
|
|
|
|
{
|
|
|
|
struct tty_ldisc *ld = tty_ldisc_ref(tty);
|
|
|
|
if (ld) {
|
|
|
|
if (ld->ops->flush_buffer)
|
|
|
|
ld->ops->flush_buffer(tty);
|
|
|
|
tty_ldisc_deref(ld);
|
|
|
|
}
|
|
|
|
tty_buffer_flush(tty);
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(tty_ldisc_flush);
|
|
|
|
|
2008-07-22 04:16:55 -06:00
|
|
|
/**
|
|
|
|
* tty_set_termios_ldisc - set ldisc field
|
|
|
|
* @tty: tty structure
|
|
|
|
* @num: 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.
|
|
|
|
*
|
2013-06-15 07:14:23 -06:00
|
|
|
* Locking: takes termios_rwsem
|
2008-07-22 04:16:55 -06:00
|
|
|
*/
|
|
|
|
|
|
|
|
static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
|
|
|
|
{
|
2013-06-15 07:14:23 -06:00
|
|
|
down_write(&tty->termios_rwsem);
|
2012-07-14 08:31:47 -06:00
|
|
|
tty->termios.c_line = num;
|
2013-06-15 07:14:23 -06:00
|
|
|
up_write(&tty->termios_rwsem);
|
2008-07-22 04:16:55 -06:00
|
|
|
}
|
|
|
|
|
2009-06-11 05:50:12 -06:00
|
|
|
/**
|
|
|
|
* 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.
|
2010-06-01 14:53:01 -06:00
|
|
|
*
|
|
|
|
* Locking: always called with BTM already held.
|
2009-06-11 05:50:12 -06:00
|
|
|
*/
|
|
|
|
|
|
|
|
static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
|
|
|
|
{
|
|
|
|
WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags));
|
2009-11-30 06:18:35 -07:00
|
|
|
if (ld->ops->open) {
|
|
|
|
int ret;
|
2010-06-01 14:53:01 -06:00
|
|
|
/* BTM here locks versus a hangup event */
|
2009-11-30 06:18:35 -07:00
|
|
|
ret = ld->ops->open(tty);
|
2010-11-24 16:27:54 -07:00
|
|
|
if (ret)
|
|
|
|
clear_bit(TTY_LDISC_OPEN, &tty->flags);
|
2009-11-30 06:18:35 -07:00
|
|
|
return ret;
|
|
|
|
}
|
2009-06-11 05:50:12 -06:00
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
|
|
* 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);
|
|
|
|
}
|
2008-07-22 04:16:55 -06:00
|
|
|
|
|
|
|
/**
|
|
|
|
* 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)
|
|
|
|
{
|
|
|
|
char buf[64];
|
2009-06-11 05:50:12 -06:00
|
|
|
struct tty_ldisc *new_ldisc;
|
|
|
|
int r;
|
2008-07-22 04:16:55 -06:00
|
|
|
|
|
|
|
/* There is an outstanding reference here so this is safe */
|
2013-06-15 05:04:48 -06:00
|
|
|
old = tty_ldisc_get(tty, old->ops->num);
|
2009-06-11 05:50:12 -06:00
|
|
|
WARN_ON(IS_ERR(old));
|
2013-03-11 14:44:42 -06:00
|
|
|
tty->ldisc = old;
|
2008-07-22 04:16:55 -06:00
|
|
|
tty_set_termios_ldisc(tty, old->ops->num);
|
2009-06-11 05:50:12 -06:00
|
|
|
if (tty_ldisc_open(tty, old) < 0) {
|
|
|
|
tty_ldisc_put(old);
|
2008-07-22 04:16:55 -06:00
|
|
|
/* This driver is always present */
|
2013-06-15 05:04:48 -06:00
|
|
|
new_ldisc = tty_ldisc_get(tty, N_TTY);
|
2009-06-11 05:50:12 -06:00
|
|
|
if (IS_ERR(new_ldisc))
|
2008-07-22 04:16:55 -06:00
|
|
|
panic("n_tty: get");
|
2013-03-11 14:44:42 -06:00
|
|
|
tty->ldisc = new_ldisc;
|
2008-07-22 04:16:55 -06:00
|
|
|
tty_set_termios_ldisc(tty, N_TTY);
|
2009-06-11 05:50:12 -06:00
|
|
|
r = tty_ldisc_open(tty, new_ldisc);
|
|
|
|
if (r < 0)
|
|
|
|
panic("Couldn't open N_TTY ldisc for "
|
|
|
|
"%s --- error %d.",
|
|
|
|
tty_name(tty, buf), r);
|
2008-07-22 04:16:55 -06:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
|
|
* 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
|
2009-06-11 05:50:12 -06:00
|
|
|
* 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.
|
2008-07-22 04:16:55 -06:00
|
|
|
*/
|
|
|
|
|
|
|
|
int tty_set_ldisc(struct tty_struct *tty, int ldisc)
|
|
|
|
{
|
|
|
|
int retval;
|
2013-06-15 05:04:49 -06:00
|
|
|
struct tty_ldisc *old_ldisc, *new_ldisc;
|
2013-06-15 05:04:48 -06:00
|
|
|
struct tty_struct *o_tty = tty->link;
|
2008-07-22 04:16:55 -06:00
|
|
|
|
2013-06-15 05:04:48 -06:00
|
|
|
new_ldisc = tty_ldisc_get(tty, ldisc);
|
2009-06-11 05:50:12 -06:00
|
|
|
if (IS_ERR(new_ldisc))
|
|
|
|
return PTR_ERR(new_ldisc);
|
2008-07-22 04:16:55 -06:00
|
|
|
|
2013-06-15 05:04:48 -06:00
|
|
|
retval = tty_ldisc_lock_pair_timeout(tty, o_tty, 5 * HZ);
|
|
|
|
if (retval) {
|
|
|
|
tty_ldisc_put(new_ldisc);
|
|
|
|
return retval;
|
|
|
|
}
|
2008-07-22 04:16:55 -06:00
|
|
|
|
2009-06-11 05:50:12 -06:00
|
|
|
/*
|
|
|
|
* Check the no-op case
|
|
|
|
*/
|
|
|
|
|
|
|
|
if (tty->ldisc->ops->num == ldisc) {
|
2013-06-15 05:04:48 -06:00
|
|
|
tty_ldisc_enable_pair(tty, o_tty);
|
2009-06-11 05:50:12 -06:00
|
|
|
tty_ldisc_put(new_ldisc);
|
2008-07-22 04:16:55 -06:00
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
2013-06-15 05:04:49 -06:00
|
|
|
old_ldisc = tty->ldisc;
|
2012-08-08 09:30:13 -06:00
|
|
|
tty_lock(tty);
|
TTY: restore tty_ldisc_wait_idle
It was removed in 65b770468e98 (tty-ldisc: turn ldisc user count into
a proper refcount), but we need to wait for last user to quit the
ldisc before we close it in tty_set_ldisc.
Otherwise weird things start to happen. There might be processes
waiting in tty_read->n_tty_read on tty->read_wait for input to appear
and at that moment, a change of ldisc is fatal. n_tty_close is called,
it frees read_buf and the waiting process is still in the middle of
reading and goes nuts after it is woken.
Previously we prevented close to happen when others are in ldisc ops
by tty_ldisc_wait_idle in tty_set_ldisc. But the commit above removed
that. So revoke the change and test whether there is 1 user (=we), and
allow the close then.
We can do that without ldisc/tty locks, because nobody else can open
the device due to TTY_LDISC_CHANGING bit set, so we in fact wait for
everybody to leave.
I don't understand why tty_ldisc_lock would be needed either when the
counter is an atomic variable, so this is a lockless
tty_ldisc_wait_idle.
On the other hand, if we fail to wait (timeout or signal), we have to
reenable the halted ldiscs, so we take ldisc lock and reuse the setup
path at the end of tty_set_ldisc.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Tested-by: Sebastian Andrzej Siewior <bigeasy@breakpoint.cc>
LKML-Reference: <20101031104136.GA511@Chamillionaire.breakpoint.cc>
LKML-Reference: <1287669539-22644-1-git-send-email-jslaby@suse.cz>
Cc: Alan Cox <alan@linux.intel.com>
Cc: stable@kernel.org [32, 33, 36]
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-10-31 16:17:51 -06:00
|
|
|
|
2013-06-15 05:04:50 -06:00
|
|
|
if (test_bit(TTY_HUPPING, &tty->flags) ||
|
|
|
|
test_bit(TTY_HUPPED, &tty->flags)) {
|
2009-06-11 05:50:12 -06:00
|
|
|
/* We were raced by the hangup method. It will have stomped
|
|
|
|
the ldisc data and closed the ldisc down */
|
2013-06-15 05:04:48 -06:00
|
|
|
tty_ldisc_enable_pair(tty, o_tty);
|
2009-06-11 05:50:12 -06:00
|
|
|
tty_ldisc_put(new_ldisc);
|
2012-08-08 09:30:13 -06:00
|
|
|
tty_unlock(tty);
|
2009-06-11 05:50:12 -06:00
|
|
|
return -EIO;
|
|
|
|
}
|
|
|
|
|
2013-06-15 05:04:49 -06:00
|
|
|
/* Shutdown the old discipline. */
|
|
|
|
tty_ldisc_close(tty, old_ldisc);
|
2008-07-22 04:16:55 -06:00
|
|
|
|
|
|
|
/* Now set up the new line discipline. */
|
2013-03-11 14:44:42 -06:00
|
|
|
tty->ldisc = new_ldisc;
|
2008-07-22 04:16:55 -06:00
|
|
|
tty_set_termios_ldisc(tty, ldisc);
|
2009-06-11 05:50:12 -06:00
|
|
|
|
|
|
|
retval = tty_ldisc_open(tty, new_ldisc);
|
2008-07-22 04:16:55 -06:00
|
|
|
if (retval < 0) {
|
2009-06-11 05:50:12 -06:00
|
|
|
/* Back to the old one or N_TTY if we can't */
|
|
|
|
tty_ldisc_put(new_ldisc);
|
2013-06-15 05:04:49 -06:00
|
|
|
tty_ldisc_restore(tty, old_ldisc);
|
2008-07-22 04:16:55 -06:00
|
|
|
}
|
2009-06-11 05:50:12 -06:00
|
|
|
|
2013-06-15 05:04:49 -06:00
|
|
|
if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc)
|
2008-07-22 04:16:55 -06:00
|
|
|
tty->ops->set_ldisc(tty);
|
|
|
|
|
2013-06-15 05:04:51 -06:00
|
|
|
/* 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. */
|
|
|
|
|
2013-06-15 05:04:49 -06:00
|
|
|
tty_ldisc_put(old_ldisc);
|
2008-07-22 04:16:55 -06:00
|
|
|
|
|
|
|
/*
|
2009-06-11 05:50:12 -06:00
|
|
|
* Allow ldisc referencing to occur again
|
2008-07-22 04:16:55 -06:00
|
|
|
*/
|
2013-06-15 05:04:48 -06:00
|
|
|
tty_ldisc_enable_pair(tty, o_tty);
|
2008-07-22 04:16:55 -06:00
|
|
|
|
2009-06-11 05:50:12 -06:00
|
|
|
/* Restart the work queue in case no characters kick it off. Safe if
|
2008-07-22 04:16:55 -06:00
|
|
|
already running */
|
2013-03-11 14:44:34 -06:00
|
|
|
schedule_work(&tty->port->buf.work);
|
|
|
|
if (o_tty)
|
2012-10-18 14:26:47 -06:00
|
|
|
schedule_work(&o_tty->port->buf.work);
|
2013-03-11 14:44:34 -06:00
|
|
|
|
2012-08-08 09:30:13 -06:00
|
|
|
tty_unlock(tty);
|
2008-07-22 04:16:55 -06:00
|
|
|
return retval;
|
|
|
|
}
|
|
|
|
|
2009-06-11 05:50:12 -06:00
|
|
|
/**
|
|
|
|
* 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)
|
|
|
|
{
|
2013-06-15 07:14:23 -06:00
|
|
|
down_write(&tty->termios_rwsem);
|
2012-07-14 08:31:47 -06:00
|
|
|
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);
|
2013-06-15 07:14:23 -06:00
|
|
|
up_write(&tty->termios_rwsem);
|
2009-06-11 05:50:12 -06:00
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
/**
|
|
|
|
* tty_ldisc_reinit - reinitialise the tty ldisc
|
|
|
|
* @tty: tty to reinit
|
2010-02-08 03:09:26 -07:00
|
|
|
* @ldisc: line discipline to reinitialize
|
2009-06-11 05:50:12 -06:00
|
|
|
*
|
2010-02-08 03:09:26 -07:00
|
|
|
* Switch the tty to a line discipline and leave the ldisc
|
|
|
|
* state closed
|
2009-06-11 05:50:12 -06:00
|
|
|
*/
|
|
|
|
|
2010-10-27 09:13:21 -06:00
|
|
|
static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc)
|
2009-06-11 05:50:12 -06:00
|
|
|
{
|
2013-06-15 05:04:48 -06:00
|
|
|
struct tty_ldisc *ld = tty_ldisc_get(tty, ldisc);
|
2010-10-27 09:13:21 -06:00
|
|
|
|
|
|
|
if (IS_ERR(ld))
|
|
|
|
return -1;
|
2009-06-11 05:50:12 -06:00
|
|
|
|
|
|
|
tty_ldisc_close(tty, tty->ldisc);
|
|
|
|
tty_ldisc_put(tty->ldisc);
|
|
|
|
/*
|
|
|
|
* Switch the line discipline back
|
|
|
|
*/
|
2013-03-11 14:44:42 -06:00
|
|
|
tty->ldisc = ld;
|
2010-02-08 03:09:26 -07:00
|
|
|
tty_set_termios_ldisc(tty, ldisc);
|
2010-10-27 09:13:21 -06:00
|
|
|
|
|
|
|
return 0;
|
2009-06-11 05:50:12 -06:00
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
|
|
* 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)
|
|
|
|
{
|
|
|
|
struct tty_ldisc *ld;
|
2010-02-08 03:09:26 -07:00
|
|
|
int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS;
|
|
|
|
int err = 0;
|
2009-06-11 05:50:12 -06:00
|
|
|
|
2013-03-11 14:44:38 -06:00
|
|
|
tty_ldisc_debug(tty, "closing ldisc: %p\n", tty->ldisc);
|
|
|
|
|
2009-06-11 05:50:12 -06:00
|
|
|
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);
|
|
|
|
}
|
2013-06-15 05:04:48 -06:00
|
|
|
|
2009-06-11 05:50:12 -06:00
|
|
|
wake_up_interruptible_poll(&tty->write_wait, POLLOUT);
|
|
|
|
wake_up_interruptible_poll(&tty->read_wait, POLLIN);
|
2013-06-15 05:04:48 -06:00
|
|
|
|
|
|
|
tty_unlock(tty);
|
|
|
|
|
2009-06-11 05:50:12 -06:00
|
|
|
/*
|
|
|
|
* Shutdown the current line discipline, and reset it to
|
2010-02-08 03:09:26 -07:00
|
|
|
* N_TTY if need be.
|
|
|
|
*
|
|
|
|
* Avoid racing set_ldisc or tty_ldisc_release
|
2009-06-11 05:50:12 -06:00
|
|
|
*/
|
2013-06-15 05:04:48 -06:00
|
|
|
tty_ldisc_lock_pair(tty, tty->link);
|
|
|
|
tty_lock(tty);
|
2010-06-01 14:53:06 -06:00
|
|
|
|
2013-06-15 05:04:48 -06:00
|
|
|
if (tty->ldisc) {
|
2013-03-11 14:44:36 -06:00
|
|
|
|
|
|
|
/* At this point we have a halted ldisc; we want to close it and
|
|
|
|
reopen a new ldisc. We could defer the reopen to the next
|
|
|
|
open but it means auditing a lot of other paths so this is
|
|
|
|
a FIXME */
|
2010-02-08 03:09:26 -07:00
|
|
|
if (reset == 0) {
|
2010-10-27 09:13:21 -06:00
|
|
|
|
2012-07-14 08:31:47 -06:00
|
|
|
if (!tty_ldisc_reinit(tty, tty->termios.c_line))
|
2010-10-27 09:13:21 -06:00
|
|
|
err = tty_ldisc_open(tty, tty->ldisc);
|
|
|
|
else
|
|
|
|
err = 1;
|
2010-02-08 03:09:26 -07:00
|
|
|
}
|
|
|
|
/* If the re-open fails or we reset then go to N_TTY. The
|
|
|
|
N_TTY open cannot fail */
|
|
|
|
if (reset || err) {
|
2010-10-27 09:13:21 -06:00
|
|
|
BUG_ON(tty_ldisc_reinit(tty, N_TTY));
|
2009-07-16 09:05:08 -06:00
|
|
|
WARN_ON(tty_ldisc_open(tty, tty->ldisc));
|
|
|
|
}
|
2009-06-11 05:50:12 -06:00
|
|
|
}
|
2013-06-15 05:04:48 -06:00
|
|
|
tty_ldisc_enable_pair(tty, tty->link);
|
2010-02-08 03:09:26 -07:00
|
|
|
if (reset)
|
|
|
|
tty_reset_termios(tty);
|
2013-03-11 14:44:38 -06:00
|
|
|
|
|
|
|
tty_ldisc_debug(tty, "re-opened ldisc: %p\n", tty->ldisc);
|
2009-06-11 05:50:12 -06:00
|
|
|
}
|
2008-07-22 04:16:55 -06:00
|
|
|
|
|
|
|
/**
|
|
|
|
* 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
|
2009-06-11 05:50:12 -06:00
|
|
|
* line disciplines and bind them to the tty. This has no locking issues
|
|
|
|
* as the device isn't yet active.
|
2008-07-22 04:16:55 -06:00
|
|
|
*/
|
|
|
|
|
|
|
|
int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty)
|
|
|
|
{
|
2009-06-11 05:50:12 -06:00
|
|
|
struct tty_ldisc *ld = tty->ldisc;
|
2008-07-22 04:16:55 -06:00
|
|
|
int retval;
|
|
|
|
|
2009-06-11 05:50:12 -06:00
|
|
|
retval = tty_ldisc_open(tty, ld);
|
|
|
|
if (retval)
|
|
|
|
return retval;
|
|
|
|
|
|
|
|
if (o_tty) {
|
|
|
|
retval = tty_ldisc_open(o_tty, o_tty->ldisc);
|
2008-07-22 04:16:55 -06:00
|
|
|
if (retval) {
|
2009-06-11 05:50:12 -06:00
|
|
|
tty_ldisc_close(tty, ld);
|
2008-07-22 04:16:55 -06:00
|
|
|
return retval;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
return 0;
|
|
|
|
}
|
2012-08-08 09:30:13 -06:00
|
|
|
|
|
|
|
static void tty_ldisc_kill(struct tty_struct *tty)
|
|
|
|
{
|
|
|
|
/*
|
|
|
|
* 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;
|
|
|
|
|
|
|
|
/* Ensure the next open requests the N_TTY ldisc */
|
|
|
|
tty_set_termios_ldisc(tty, N_TTY);
|
|
|
|
}
|
|
|
|
|
2008-07-22 04:16:55 -06:00
|
|
|
/**
|
|
|
|
* tty_ldisc_release - release line discipline
|
|
|
|
* @tty: tty being shut down
|
|
|
|
* @o_tty: pair tty for pty/tty pairs
|
|
|
|
*
|
2009-06-11 05:51:41 -06:00
|
|
|
* Called during the final close of a tty/pty pair in order to shut down
|
|
|
|
* the line discpline layer. On exit the ldisc assigned is N_TTY and the
|
2009-06-11 05:50:12 -06:00
|
|
|
* ldisc has not been opened.
|
2008-07-22 04:16:55 -06:00
|
|
|
*/
|
|
|
|
|
|
|
|
void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
|
|
|
|
{
|
|
|
|
/*
|
2013-03-11 14:44:35 -06:00
|
|
|
* Shutdown this line discipline. As this is the final close,
|
|
|
|
* it does not race with the set_ldisc code path.
|
2008-07-22 04:16:55 -06:00
|
|
|
*/
|
|
|
|
|
2013-03-11 14:44:38 -06:00
|
|
|
tty_ldisc_debug(tty, "closing ldisc: %p\n", tty->ldisc);
|
|
|
|
|
2013-06-15 05:04:48 -06:00
|
|
|
tty_ldisc_lock_pair(tty, o_tty);
|
2012-12-25 15:02:48 -07:00
|
|
|
tty_lock_pair(tty, o_tty);
|
2013-06-15 05:04:48 -06:00
|
|
|
|
2012-08-08 09:30:13 -06:00
|
|
|
tty_ldisc_kill(tty);
|
2009-06-11 05:50:12 -06:00
|
|
|
if (o_tty)
|
2012-08-08 09:30:13 -06:00
|
|
|
tty_ldisc_kill(o_tty);
|
2009-06-29 08:21:47 -06:00
|
|
|
|
2012-08-08 09:30:13 -06:00
|
|
|
tty_unlock_pair(tty, o_tty);
|
2013-06-15 05:04:48 -06:00
|
|
|
tty_ldisc_unlock_pair(tty, o_tty);
|
|
|
|
|
2009-06-29 08:21:47 -06:00
|
|
|
/* And the memory resources remaining (buffers, termios) will be
|
|
|
|
disposed of when the kref hits zero */
|
2013-03-11 14:44:38 -06:00
|
|
|
|
|
|
|
tty_ldisc_debug(tty, "ldisc closed\n");
|
2008-07-22 04:16:55 -06:00
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
|
|
* 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)
|
|
|
|
{
|
2013-06-15 05:04:48 -06:00
|
|
|
struct tty_ldisc *ld = tty_ldisc_get(tty, N_TTY);
|
2009-06-11 05:50:12 -06:00
|
|
|
if (IS_ERR(ld))
|
2008-07-22 04:16:55 -06:00
|
|
|
panic("n_tty: init_tty");
|
2013-03-11 14:44:42 -06:00
|
|
|
tty->ldisc = ld;
|
2008-07-22 04:16:55 -06:00
|
|
|
}
|
|
|
|
|
2011-03-23 03:48:35 -06:00
|
|
|
/**
|
|
|
|
* tty_ldisc_init - 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)
|
|
|
|
{
|
2013-03-11 14:44:40 -06:00
|
|
|
tty_ldisc_put(tty->ldisc);
|
2013-03-11 14:44:42 -06:00
|
|
|
tty->ldisc = NULL;
|
2011-03-23 03:48:35 -06:00
|
|
|
}
|
|
|
|
|
2008-07-22 04:16:55 -06:00
|
|
|
void tty_ldisc_begin(void)
|
|
|
|
{
|
|
|
|
/* Setup the default TTY line discipline. */
|
|
|
|
(void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY);
|
|
|
|
}
|