mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-05 21:36:44 +07:00
c97399418a
The global "normal" spin lock that guards the line discipline administration is replaced by a raw spin lock. On a PREEMPT_RT system this prevents unwanted scheduling overhead around the line discipline administration. On a 200 MHz AT91SAM9261 processor setup this fixes about 100us of scheduling overhead on a TTY read or write call. Signed-off-by: Ivo Sieben <meltedpianoman@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
990 lines
24 KiB
C
990 lines
24 KiB
C
#include <linux/types.h>
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#include <linux/errno.h>
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#include <linux/kmod.h>
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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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#include <linux/ratelimit.h>
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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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static DEFINE_RAW_SPINLOCK(tty_ldisc_lock);
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static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait);
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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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static inline struct tty_ldisc *get_ldisc(struct tty_ldisc *ld)
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{
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if (ld)
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atomic_inc(&ld->users);
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return ld;
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}
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static void put_ldisc(struct tty_ldisc *ld)
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{
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unsigned long flags;
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if (WARN_ON_ONCE(!ld))
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return;
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/*
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* If this is the last user, free the ldisc, and
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* release the ldisc ops.
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*
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* We really want an "atomic_dec_and_raw_lock_irqsave()",
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* but we don't have it, so this does it by hand.
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*/
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raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
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if (atomic_dec_and_test(&ld->users)) {
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struct tty_ldisc_ops *ldo = ld->ops;
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ldo->refcount--;
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module_put(ldo->owner);
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raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
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kfree(ld);
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return;
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}
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raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
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wake_up(&ld->wq_idle);
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}
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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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* takes tty_ldisc_lock to guard against ldisc races
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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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raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
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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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raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
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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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* takes tty_ldisc_lock to guard against ldisc races
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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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raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
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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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raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
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return ret;
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}
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EXPORT_SYMBOL(tty_unregister_ldisc);
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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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raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
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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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raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
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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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raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
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ldops->refcount--;
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module_put(ldops->owner);
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raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
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}
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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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* takes tty_ldisc_lock to guard against ldisc races
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*/
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static struct tty_ldisc *tty_ldisc_get(int disc)
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{
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struct tty_ldisc *ld;
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struct tty_ldisc_ops *ldops;
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if (disc < N_TTY || disc >= NR_LDISCS)
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return ERR_PTR(-EINVAL);
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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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request_module("tty-ldisc-%d", disc);
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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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}
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ld->ops = ldops;
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atomic_set(&ld->users, 1);
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init_waitqueue_head(&ld->wq_idle);
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return ld;
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}
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static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos)
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{
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return (*pos < NR_LDISCS) ? pos : NULL;
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}
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static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos)
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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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struct tty_ldisc_ops *ldops;
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ldops = get_ldops(i);
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if (IS_ERR(ldops))
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return 0;
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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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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_assign - set ldisc on a tty
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* @tty: tty to assign
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* @ld: line discipline
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*
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* Install an instance of a line discipline into a tty structure. The
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* ldisc must have a reference count above zero to ensure it remains.
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* The tty instance refcount starts at zero.
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*
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* Locking:
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* Caller must hold references
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*/
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static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld)
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{
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tty->ldisc = ld;
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}
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/**
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* tty_ldisc_try - internal helper
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* @tty: the tty
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*
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* Make a single attempt to grab and bump the refcount on
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* the tty ldisc. Return 0 on failure or 1 on success. This is
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* used to implement both the waiting and non waiting versions
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* of tty_ldisc_ref
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*
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* Locking: takes tty_ldisc_lock
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*/
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static struct tty_ldisc *tty_ldisc_try(struct tty_struct *tty)
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{
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unsigned long flags;
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struct tty_ldisc *ld;
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raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
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ld = NULL;
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if (test_bit(TTY_LDISC, &tty->flags))
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ld = get_ldisc(tty->ldisc);
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raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
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return ld;
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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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* Locking: call functions take tty_ldisc_lock
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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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struct tty_ldisc *ld;
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/* wait_event is a macro */
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wait_event(tty_ldisc_wait, (ld = tty_ldisc_try(tty)) != NULL);
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return ld;
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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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* Locking: called functions take tty_ldisc_lock
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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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return tty_ldisc_try(tty);
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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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* Locking: takes tty_ldisc_lock
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*/
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void tty_ldisc_deref(struct tty_ldisc *ld)
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{
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put_ldisc(ld);
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}
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EXPORT_SYMBOL_GPL(tty_ldisc_deref);
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static inline void tty_ldisc_put(struct tty_ldisc *ld)
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{
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put_ldisc(ld);
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}
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/**
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* tty_ldisc_enable - allow ldisc use
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* @tty: terminal to activate ldisc on
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*
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* Set the TTY_LDISC flag when the line discipline can be called
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* again. Do necessary wakeups for existing sleepers. Clear the LDISC
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* changing flag to indicate any ldisc change is now over.
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*
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* Note: nobody should set the TTY_LDISC bit except via this function.
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* Clearing directly is allowed.
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*/
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void tty_ldisc_enable(struct tty_struct *tty)
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{
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set_bit(TTY_LDISC, &tty->flags);
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clear_bit(TTY_LDISC_CHANGING, &tty->flags);
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wake_up(&tty_ldisc_wait);
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}
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/**
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* tty_ldisc_flush - flush line discipline queue
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* @tty: tty
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*
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* Flush the line discipline queue (if any) for this tty. If there
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* is no line discipline active this is a no-op.
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*/
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void tty_ldisc_flush(struct tty_struct *tty)
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{
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struct tty_ldisc *ld = tty_ldisc_ref(tty);
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if (ld) {
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if (ld->ops->flush_buffer)
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ld->ops->flush_buffer(tty);
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tty_ldisc_deref(ld);
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}
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tty_buffer_flush(tty);
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}
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EXPORT_SYMBOL_GPL(tty_ldisc_flush);
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/**
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* tty_set_termios_ldisc - set ldisc field
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* @tty: tty structure
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* @num: line discipline number
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*
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* This is probably overkill for real world processors but
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* they are not on hot paths so a little discipline won't do
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* any harm.
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*
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* Locking: takes termios_mutex
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*/
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static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
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{
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mutex_lock(&tty->termios_mutex);
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tty->termios.c_line = num;
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mutex_unlock(&tty->termios_mutex);
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}
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/**
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* tty_ldisc_open - open a line discipline
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* @tty: tty we are opening the ldisc on
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* @ld: discipline to open
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*
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* A helper opening method. Also a convenient debugging and check
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* point.
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*
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* Locking: always called with BTM already held.
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*/
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static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
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{
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WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags));
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if (ld->ops->open) {
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int ret;
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/* BTM here locks versus a hangup event */
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ret = ld->ops->open(tty);
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if (ret)
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clear_bit(TTY_LDISC_OPEN, &tty->flags);
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return ret;
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}
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return 0;
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}
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/**
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* tty_ldisc_close - close a line discipline
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* @tty: tty we are opening the ldisc on
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* @ld: discipline to close
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*
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* A helper close method. Also a convenient debugging and check
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* point.
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*/
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static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld)
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{
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WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags));
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clear_bit(TTY_LDISC_OPEN, &tty->flags);
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if (ld->ops->close)
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ld->ops->close(tty);
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}
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/**
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* tty_ldisc_restore - helper for tty ldisc change
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* @tty: tty to recover
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* @old: previous ldisc
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*
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* Restore the previous line discipline or N_TTY when a line discipline
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* change fails due to an open error
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*/
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static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old)
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{
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char buf[64];
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struct tty_ldisc *new_ldisc;
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int r;
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/* There is an outstanding reference here so this is safe */
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old = tty_ldisc_get(old->ops->num);
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WARN_ON(IS_ERR(old));
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tty_ldisc_assign(tty, old);
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tty_set_termios_ldisc(tty, old->ops->num);
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if (tty_ldisc_open(tty, old) < 0) {
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tty_ldisc_put(old);
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/* This driver is always present */
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new_ldisc = tty_ldisc_get(N_TTY);
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if (IS_ERR(new_ldisc))
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panic("n_tty: get");
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tty_ldisc_assign(tty, new_ldisc);
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tty_set_termios_ldisc(tty, N_TTY);
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r = tty_ldisc_open(tty, new_ldisc);
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if (r < 0)
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panic("Couldn't open N_TTY ldisc for "
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"%s --- error %d.",
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tty_name(tty, buf), r);
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}
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}
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/**
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* tty_ldisc_halt - shut down the line discipline
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* @tty: tty device
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*
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* Shut down the line discipline and work queue for this tty device.
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* The TTY_LDISC flag being cleared ensures no further references can
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* be obtained while the delayed work queue halt ensures that no more
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* data is fed to the ldisc.
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*
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* You need to do a 'flush_scheduled_work()' (outside the ldisc_mutex)
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* in order to make sure any currently executing ldisc work is also
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* flushed.
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*/
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static int tty_ldisc_halt(struct tty_struct *tty)
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{
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clear_bit(TTY_LDISC, &tty->flags);
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return cancel_work_sync(&tty->port->buf.work);
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}
|
|
|
|
/**
|
|
* tty_ldisc_flush_works - flush all works of a tty
|
|
* @tty: tty device to flush works for
|
|
*
|
|
* Sync flush all works belonging to @tty.
|
|
*/
|
|
static void tty_ldisc_flush_works(struct tty_struct *tty)
|
|
{
|
|
flush_work(&tty->hangup_work);
|
|
flush_work(&tty->SAK_work);
|
|
flush_work(&tty->port->buf.work);
|
|
}
|
|
|
|
/**
|
|
* tty_ldisc_wait_idle - wait for the ldisc to become idle
|
|
* @tty: tty to wait for
|
|
* @timeout: for how long to wait at most
|
|
*
|
|
* Wait for the line discipline to become idle. The discipline must
|
|
* have been halted for this to guarantee it remains idle.
|
|
*/
|
|
static int tty_ldisc_wait_idle(struct tty_struct *tty, long timeout)
|
|
{
|
|
long ret;
|
|
ret = wait_event_timeout(tty->ldisc->wq_idle,
|
|
atomic_read(&tty->ldisc->users) == 1, timeout);
|
|
return ret > 0 ? 0 : -EBUSY;
|
|
}
|
|
|
|
/**
|
|
* 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.
|
|
*
|
|
* Locking: takes tty_ldisc_lock, termios_mutex
|
|
*/
|
|
|
|
int tty_set_ldisc(struct tty_struct *tty, int ldisc)
|
|
{
|
|
int retval;
|
|
struct tty_ldisc *o_ldisc, *new_ldisc;
|
|
int work, o_work = 0;
|
|
struct tty_struct *o_tty;
|
|
|
|
new_ldisc = tty_ldisc_get(ldisc);
|
|
if (IS_ERR(new_ldisc))
|
|
return PTR_ERR(new_ldisc);
|
|
|
|
tty_lock(tty);
|
|
/*
|
|
* We need to look at the tty locking here for pty/tty pairs
|
|
* when both sides try to change in parallel.
|
|
*/
|
|
|
|
o_tty = tty->link; /* o_tty is the pty side or NULL */
|
|
|
|
|
|
/*
|
|
* Check the no-op case
|
|
*/
|
|
|
|
if (tty->ldisc->ops->num == ldisc) {
|
|
tty_unlock(tty);
|
|
tty_ldisc_put(new_ldisc);
|
|
return 0;
|
|
}
|
|
|
|
tty_unlock(tty);
|
|
/*
|
|
* Problem: What do we do if this blocks ?
|
|
* We could deadlock here
|
|
*/
|
|
|
|
tty_wait_until_sent(tty, 0);
|
|
|
|
tty_lock(tty);
|
|
mutex_lock(&tty->ldisc_mutex);
|
|
|
|
/*
|
|
* We could be midstream of another ldisc change which has
|
|
* dropped the lock during processing. If so we need to wait.
|
|
*/
|
|
|
|
while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) {
|
|
mutex_unlock(&tty->ldisc_mutex);
|
|
tty_unlock(tty);
|
|
wait_event(tty_ldisc_wait,
|
|
test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0);
|
|
tty_lock(tty);
|
|
mutex_lock(&tty->ldisc_mutex);
|
|
}
|
|
|
|
set_bit(TTY_LDISC_CHANGING, &tty->flags);
|
|
|
|
/*
|
|
* No more input please, we are switching. The new ldisc
|
|
* will update this value in the ldisc open function
|
|
*/
|
|
|
|
tty->receive_room = 0;
|
|
|
|
o_ldisc = tty->ldisc;
|
|
|
|
tty_unlock(tty);
|
|
/*
|
|
* Make sure we don't change while someone holds a
|
|
* reference to the line discipline. The TTY_LDISC bit
|
|
* prevents anyone taking a reference once it is clear.
|
|
* We need the lock to avoid racing reference takers.
|
|
*
|
|
* We must clear the TTY_LDISC bit here to avoid a livelock
|
|
* with a userspace app continually trying to use the tty in
|
|
* parallel to the change and re-referencing the tty.
|
|
*/
|
|
|
|
work = tty_ldisc_halt(tty);
|
|
if (o_tty)
|
|
o_work = tty_ldisc_halt(o_tty);
|
|
|
|
/*
|
|
* Wait for ->hangup_work and ->buf.work handlers to terminate.
|
|
* We must drop the mutex here in case a hangup is also in process.
|
|
*/
|
|
|
|
mutex_unlock(&tty->ldisc_mutex);
|
|
|
|
tty_ldisc_flush_works(tty);
|
|
|
|
retval = tty_ldisc_wait_idle(tty, 5 * HZ);
|
|
|
|
tty_lock(tty);
|
|
mutex_lock(&tty->ldisc_mutex);
|
|
|
|
/* handle wait idle failure locked */
|
|
if (retval) {
|
|
tty_ldisc_put(new_ldisc);
|
|
goto enable;
|
|
}
|
|
|
|
if (test_bit(TTY_HUPPING, &tty->flags)) {
|
|
/* We were raced by the hangup method. It will have stomped
|
|
the ldisc data and closed the ldisc down */
|
|
clear_bit(TTY_LDISC_CHANGING, &tty->flags);
|
|
mutex_unlock(&tty->ldisc_mutex);
|
|
tty_ldisc_put(new_ldisc);
|
|
tty_unlock(tty);
|
|
return -EIO;
|
|
}
|
|
|
|
/* Shutdown the current discipline. */
|
|
tty_ldisc_close(tty, o_ldisc);
|
|
|
|
/* Now set up the new line discipline. */
|
|
tty_ldisc_assign(tty, new_ldisc);
|
|
tty_set_termios_ldisc(tty, ldisc);
|
|
|
|
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, o_ldisc);
|
|
}
|
|
|
|
/* At this point we hold a reference to the new ldisc and a
|
|
a reference to the old ldisc. If we ended up flipping back
|
|
to the existing ldisc we have two references to it */
|
|
|
|
if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc)
|
|
tty->ops->set_ldisc(tty);
|
|
|
|
tty_ldisc_put(o_ldisc);
|
|
|
|
enable:
|
|
/*
|
|
* Allow ldisc referencing to occur again
|
|
*/
|
|
|
|
tty_ldisc_enable(tty);
|
|
if (o_tty)
|
|
tty_ldisc_enable(o_tty);
|
|
|
|
/* Restart the work queue in case no characters kick it off. Safe if
|
|
already running */
|
|
if (work)
|
|
schedule_work(&tty->port->buf.work);
|
|
if (o_work)
|
|
schedule_work(&o_tty->port->buf.work);
|
|
mutex_unlock(&tty->ldisc_mutex);
|
|
tty_unlock(tty);
|
|
return retval;
|
|
}
|
|
|
|
/**
|
|
* 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)
|
|
{
|
|
mutex_lock(&tty->termios_mutex);
|
|
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);
|
|
mutex_unlock(&tty->termios_mutex);
|
|
}
|
|
|
|
|
|
/**
|
|
* tty_ldisc_reinit - reinitialise the tty ldisc
|
|
* @tty: tty to reinit
|
|
* @ldisc: line discipline to reinitialize
|
|
*
|
|
* Switch the tty to a line discipline and leave the ldisc
|
|
* state closed
|
|
*/
|
|
|
|
static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc)
|
|
{
|
|
struct tty_ldisc *ld = tty_ldisc_get(ldisc);
|
|
|
|
if (IS_ERR(ld))
|
|
return -1;
|
|
|
|
tty_ldisc_close(tty, tty->ldisc);
|
|
tty_ldisc_put(tty->ldisc);
|
|
tty->ldisc = NULL;
|
|
/*
|
|
* Switch the line discipline back
|
|
*/
|
|
tty_ldisc_assign(tty, ld);
|
|
tty_set_termios_ldisc(tty, ldisc);
|
|
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* 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;
|
|
int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS;
|
|
int err = 0;
|
|
|
|
/*
|
|
* FIXME! What are the locking issues here? This may me overdoing
|
|
* things... This question is especially important now that we've
|
|
* removed the irqlock.
|
|
*/
|
|
ld = tty_ldisc_ref(tty);
|
|
if (ld != NULL) {
|
|
/* We may have no line discipline at this point */
|
|
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);
|
|
}
|
|
/*
|
|
* FIXME: Once we trust the LDISC code better we can wait here for
|
|
* ldisc completion and fix the driver call race
|
|
*/
|
|
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
|
|
*/
|
|
mutex_lock(&tty->ldisc_mutex);
|
|
|
|
/*
|
|
* this is like tty_ldisc_halt, but we need to give up
|
|
* the BTM before calling cancel_work_sync, which may
|
|
* need to wait for another function taking the BTM
|
|
*/
|
|
clear_bit(TTY_LDISC, &tty->flags);
|
|
tty_unlock(tty);
|
|
cancel_work_sync(&tty->port->buf.work);
|
|
mutex_unlock(&tty->ldisc_mutex);
|
|
retry:
|
|
tty_lock(tty);
|
|
mutex_lock(&tty->ldisc_mutex);
|
|
|
|
/* At this point we have a closed ldisc and we want to
|
|
reopen it. We could defer this to the next open but
|
|
it means auditing a lot of other paths so this is
|
|
a FIXME */
|
|
if (tty->ldisc) { /* Not yet closed */
|
|
if (atomic_read(&tty->ldisc->users) != 1) {
|
|
char cur_n[TASK_COMM_LEN], tty_n[64];
|
|
long timeout = 3 * HZ;
|
|
tty_unlock(tty);
|
|
|
|
while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) {
|
|
timeout = MAX_SCHEDULE_TIMEOUT;
|
|
printk_ratelimited(KERN_WARNING
|
|
"%s: waiting (%s) for %s took too long, but we keep waiting...\n",
|
|
__func__, get_task_comm(cur_n, current),
|
|
tty_name(tty, tty_n));
|
|
}
|
|
mutex_unlock(&tty->ldisc_mutex);
|
|
goto retry;
|
|
}
|
|
|
|
if (reset == 0) {
|
|
|
|
if (!tty_ldisc_reinit(tty, tty->termios.c_line))
|
|
err = tty_ldisc_open(tty, tty->ldisc);
|
|
else
|
|
err = 1;
|
|
}
|
|
/* If the re-open fails or we reset then go to N_TTY. The
|
|
N_TTY open cannot fail */
|
|
if (reset || err) {
|
|
BUG_ON(tty_ldisc_reinit(tty, N_TTY));
|
|
WARN_ON(tty_ldisc_open(tty, tty->ldisc));
|
|
}
|
|
tty_ldisc_enable(tty);
|
|
}
|
|
mutex_unlock(&tty->ldisc_mutex);
|
|
if (reset)
|
|
tty_reset_termios(tty);
|
|
}
|
|
|
|
/**
|
|
* 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)
|
|
{
|
|
struct tty_ldisc *ld = tty->ldisc;
|
|
int retval;
|
|
|
|
retval = tty_ldisc_open(tty, ld);
|
|
if (retval)
|
|
return retval;
|
|
|
|
if (o_tty) {
|
|
retval = tty_ldisc_open(o_tty, o_tty->ldisc);
|
|
if (retval) {
|
|
tty_ldisc_close(tty, ld);
|
|
return retval;
|
|
}
|
|
tty_ldisc_enable(o_tty);
|
|
}
|
|
tty_ldisc_enable(tty);
|
|
return 0;
|
|
}
|
|
|
|
static void tty_ldisc_kill(struct tty_struct *tty)
|
|
{
|
|
/* There cannot be users from userspace now. But there still might be
|
|
* drivers holding a reference via tty_ldisc_ref. Do not steal them the
|
|
* ldisc until they are done. */
|
|
tty_ldisc_wait_idle(tty, MAX_SCHEDULE_TIMEOUT);
|
|
|
|
mutex_lock(&tty->ldisc_mutex);
|
|
/*
|
|
* 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);
|
|
mutex_unlock(&tty->ldisc_mutex);
|
|
}
|
|
|
|
/**
|
|
* tty_ldisc_release - release line discipline
|
|
* @tty: tty being shut down
|
|
* @o_tty: pair tty for pty/tty pairs
|
|
*
|
|
* 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
|
|
* ldisc has not been opened.
|
|
*/
|
|
|
|
void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
|
|
{
|
|
/*
|
|
* Prevent flush_to_ldisc() from rescheduling the work for later. Then
|
|
* kill any delayed work. As this is the final close it does not
|
|
* race with the set_ldisc code path.
|
|
*/
|
|
|
|
tty_lock_pair(tty, o_tty);
|
|
tty_ldisc_halt(tty);
|
|
tty_ldisc_flush_works(tty);
|
|
if (o_tty) {
|
|
tty_ldisc_halt(o_tty);
|
|
tty_ldisc_flush_works(o_tty);
|
|
}
|
|
|
|
/* This will need doing differently if we need to lock */
|
|
tty_ldisc_kill(tty);
|
|
|
|
if (o_tty)
|
|
tty_ldisc_kill(o_tty);
|
|
|
|
tty_unlock_pair(tty, o_tty);
|
|
/* And the memory resources remaining (buffers, termios) will be
|
|
disposed of when the kref hits zero */
|
|
}
|
|
|
|
/**
|
|
* 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(N_TTY);
|
|
if (IS_ERR(ld))
|
|
panic("n_tty: init_tty");
|
|
tty_ldisc_assign(tty, ld);
|
|
}
|
|
|
|
/**
|
|
* 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)
|
|
{
|
|
put_ldisc(tty->ldisc);
|
|
tty_ldisc_assign(tty, NULL);
|
|
}
|
|
|
|
void tty_ldisc_begin(void)
|
|
{
|
|
/* Setup the default TTY line discipline. */
|
|
(void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY);
|
|
}
|