tty: Split ldisc code into its own file
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 82f6a8c..d27a08b 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -656,558 +656,6 @@
/**
- * 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.
- *
- * Locking: takes termios_mutex
- */
-
-static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
-{
- mutex_lock(&tty->termios_mutex);
- tty->termios->c_line = num;
- mutex_unlock(&tty->termios_mutex);
-}
-
-/*
- * This guards the refcounted line discipline lists. The lock
- * must be taken with irqs off because there are hangup path
- * callers who will do ldisc lookups and cannot sleep.
- */
-
-static DEFINE_SPINLOCK(tty_ldisc_lock);
-static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait);
-/* Line disc dispatch table */
-static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS];
-
-/**
- * tty_register_ldisc - install a line discipline
- * @disc: ldisc number
- * @new_ldisc: pointer to the ldisc object
- *
- * Installs a new line discipline into the kernel. The discipline
- * is set up as unreferenced and then made available to the kernel
- * from this point onwards.
- *
- * Locking:
- * takes tty_ldisc_lock to guard against ldisc races
- */
-
-int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc)
-{
- unsigned long flags;
- int ret = 0;
-
- if (disc < N_TTY || disc >= NR_LDISCS)
- return -EINVAL;
-
- spin_lock_irqsave(&tty_ldisc_lock, flags);
- tty_ldiscs[disc] = new_ldisc;
- new_ldisc->num = disc;
- new_ldisc->refcount = 0;
- spin_unlock_irqrestore(&tty_ldisc_lock, flags);
-
- return ret;
-}
-EXPORT_SYMBOL(tty_register_ldisc);
-
-/**
- * tty_unregister_ldisc - unload a line discipline
- * @disc: ldisc number
- * @new_ldisc: pointer to the ldisc object
- *
- * Remove a line discipline from the kernel providing it is not
- * currently in use.
- *
- * Locking:
- * takes tty_ldisc_lock to guard against ldisc races
- */
-
-int tty_unregister_ldisc(int disc)
-{
- unsigned long flags;
- int ret = 0;
-
- if (disc < N_TTY || disc >= NR_LDISCS)
- return -EINVAL;
-
- spin_lock_irqsave(&tty_ldisc_lock, flags);
- if (tty_ldiscs[disc]->refcount)
- ret = -EBUSY;
- else
- tty_ldiscs[disc] = NULL;
- spin_unlock_irqrestore(&tty_ldisc_lock, flags);
-
- return ret;
-}
-EXPORT_SYMBOL(tty_unregister_ldisc);
-
-
-/**
- * tty_ldisc_try_get - try and reference an ldisc
- * @disc: ldisc number
- * @ld: tty ldisc structure to complete
- *
- * Attempt to open and lock a line discipline into place. Return
- * the line discipline refcounted and assigned in ld. On an error
- * report the error code back
- */
-
-static int tty_ldisc_try_get(int disc, struct tty_ldisc *ld)
-{
- unsigned long flags;
- struct tty_ldisc_ops *ldops;
- int err = -EINVAL;
-
- spin_lock_irqsave(&tty_ldisc_lock, flags);
- ld->ops = NULL;
- ldops = tty_ldiscs[disc];
- /* Check the entry is defined */
- if (ldops) {
- /* If the module is being unloaded we can't use it */
- if (!try_module_get(ldops->owner))
- err = -EAGAIN;
- else {
- /* lock it */
- ldops->refcount++;
- ld->ops = ldops;
- err = 0;
- }
- }
- spin_unlock_irqrestore(&tty_ldisc_lock, flags);
- return err;
-}
-
-/**
- * tty_ldisc_get - take a reference to an ldisc
- * @disc: ldisc number
- * @ld: tty line discipline structure to use
- *
- * Takes a reference to a line discipline. Deals with refcounts and
- * module locking counts. Returns NULL if the discipline is not available.
- * Returns a pointer to the discipline and bumps the ref count if it is
- * available
- *
- * Locking:
- * takes tty_ldisc_lock to guard against ldisc races
- */
-
-static int tty_ldisc_get(int disc, struct tty_ldisc *ld)
-{
- int err;
-
- if (disc < N_TTY || disc >= NR_LDISCS)
- return -EINVAL;
- err = tty_ldisc_try_get(disc, ld);
- if (err == -EAGAIN) {
- request_module("tty-ldisc-%d", disc);
- err = tty_ldisc_try_get(disc, ld);
- }
- return err;
-}
-
-/**
- * tty_ldisc_put - drop ldisc reference
- * @disc: ldisc number
- *
- * Drop a reference to a line discipline. Manage refcounts and
- * module usage counts
- *
- * Locking:
- * takes tty_ldisc_lock to guard against ldisc races
- */
-
-static void tty_ldisc_put(struct tty_ldisc_ops *ld)
-{
- unsigned long flags;
- int disc = ld->num;
-
- BUG_ON(disc < N_TTY || disc >= NR_LDISCS);
-
- spin_lock_irqsave(&tty_ldisc_lock, flags);
- ld = tty_ldiscs[disc];
- BUG_ON(ld->refcount == 0);
- ld->refcount--;
- module_put(ld->owner);
- spin_unlock_irqrestore(&tty_ldisc_lock, flags);
-}
-
-static void * tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos)
-{
- return (*pos < NR_LDISCS) ? pos : NULL;
-}
-
-static void * tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos)
-{
- (*pos)++;
- return (*pos < NR_LDISCS) ? pos : NULL;
-}
-
-static void tty_ldiscs_seq_stop(struct seq_file *m, void *v)
-{
-}
-
-static int tty_ldiscs_seq_show(struct seq_file *m, void *v)
-{
- int i = *(loff_t *)v;
- struct tty_ldisc ld;
-
- if (tty_ldisc_get(i, &ld) < 0)
- return 0;
- seq_printf(m, "%-10s %2d\n", ld.ops->name ? ld.ops->name : "???", i);
- tty_ldisc_put(ld.ops);
- return 0;
-}
-
-static const struct seq_operations tty_ldiscs_seq_ops = {
- .start = tty_ldiscs_seq_start,
- .next = tty_ldiscs_seq_next,
- .stop = tty_ldiscs_seq_stop,
- .show = tty_ldiscs_seq_show,
-};
-
-static int proc_tty_ldiscs_open(struct inode *inode, struct file *file)
-{
- return seq_open(file, &tty_ldiscs_seq_ops);
-}
-
-const struct file_operations tty_ldiscs_proc_fops = {
- .owner = THIS_MODULE,
- .open = proc_tty_ldiscs_open,
- .read = seq_read,
- .llseek = seq_lseek,
- .release = seq_release,
-};
-
-/**
- * tty_ldisc_assign - set ldisc on a tty
- * @tty: tty to assign
- * @ld: line discipline
- *
- * Install an instance of a line discipline into a tty structure. The
- * ldisc must have a reference count above zero to ensure it remains/
- * The tty instance refcount starts at zero.
- *
- * Locking:
- * Caller must hold references
- */
-
-static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld)
-{
- ld->refcount = 0;
- tty->ldisc = *ld;
-}
-
-/**
- * tty_ldisc_try - internal helper
- * @tty: the tty
- *
- * Make a single attempt to grab and bump the refcount on
- * the tty ldisc. Return 0 on failure or 1 on success. This is
- * used to implement both the waiting and non waiting versions
- * of tty_ldisc_ref
- *
- * Locking: takes tty_ldisc_lock
- */
-
-static int tty_ldisc_try(struct tty_struct *tty)
-{
- unsigned long flags;
- struct tty_ldisc *ld;
- int ret = 0;
-
- spin_lock_irqsave(&tty_ldisc_lock, flags);
- ld = &tty->ldisc;
- if (test_bit(TTY_LDISC, &tty->flags)) {
- ld->refcount++;
- ret = 1;
- }
- spin_unlock_irqrestore(&tty_ldisc_lock, flags);
- return ret;
-}
-
-/**
- * tty_ldisc_ref_wait - wait for the tty ldisc
- * @tty: tty device
- *
- * Dereference the line discipline for the terminal and take a
- * reference to it. If the line discipline is in flux then
- * wait patiently until it changes.
- *
- * Note: Must not be called from an IRQ/timer context. The caller
- * must also be careful not to hold other locks that will deadlock
- * against a discipline change, such as an existing ldisc reference
- * (which we check for)
- *
- * Locking: call functions take tty_ldisc_lock
- */
-
-struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
-{
- /* wait_event is a macro */
- wait_event(tty_ldisc_wait, tty_ldisc_try(tty));
- if (tty->ldisc.refcount == 0)
- printk(KERN_ERR "tty_ldisc_ref_wait\n");
- return &tty->ldisc;
-}
-
-EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);
-
-/**
- * tty_ldisc_ref - get the tty ldisc
- * @tty: tty device
- *
- * Dereference the line discipline for the terminal and take a
- * reference to it. If the line discipline is in flux then
- * return NULL. Can be called from IRQ and timer functions.
- *
- * Locking: called functions take tty_ldisc_lock
- */
-
-struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty)
-{
- if (tty_ldisc_try(tty))
- return &tty->ldisc;
- return NULL;
-}
-
-EXPORT_SYMBOL_GPL(tty_ldisc_ref);
-
-/**
- * tty_ldisc_deref - free a tty ldisc reference
- * @ld: reference to free up
- *
- * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May
- * be called in IRQ context.
- *
- * Locking: takes tty_ldisc_lock
- */
-
-void tty_ldisc_deref(struct tty_ldisc *ld)
-{
- unsigned long flags;
-
- BUG_ON(ld == NULL);
-
- spin_lock_irqsave(&tty_ldisc_lock, flags);
- if (ld->refcount == 0)
- printk(KERN_ERR "tty_ldisc_deref: no references.\n");
- else
- ld->refcount--;
- if (ld->refcount == 0)
- wake_up(&tty_ldisc_wait);
- spin_unlock_irqrestore(&tty_ldisc_lock, flags);
-}
-
-EXPORT_SYMBOL_GPL(tty_ldisc_deref);
-
-/**
- * tty_ldisc_enable - allow ldisc use
- * @tty: terminal to activate ldisc on
- *
- * Set the TTY_LDISC flag when the line discipline can be called
- * again. Do necessary wakeups for existing sleepers.
- *
- * Note: nobody should set this bit except via this function. Clearing
- * directly is allowed.
- */
-
-static void tty_ldisc_enable(struct tty_struct *tty)
-{
- set_bit(TTY_LDISC, &tty->flags);
- wake_up(&tty_ldisc_wait);
-}
-
-/**
- * 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];
- struct tty_ldisc new_ldisc;
-
- /* There is an outstanding reference here so this is safe */
- tty_ldisc_get(old->ops->num, old);
- tty_ldisc_assign(tty, old);
- tty_set_termios_ldisc(tty, old->ops->num);
- if (old->ops->open && (old->ops->open(tty) < 0)) {
- tty_ldisc_put(old->ops);
- /* This driver is always present */
- if (tty_ldisc_get(N_TTY, &new_ldisc) < 0)
- panic("n_tty: get");
- tty_ldisc_assign(tty, &new_ldisc);
- tty_set_termios_ldisc(tty, N_TTY);
- if (new_ldisc.ops->open) {
- int r = new_ldisc.ops->open(tty);
- if (r < 0)
- panic("Couldn't open N_TTY ldisc for "
- "%s --- error %d.",
- tty_name(tty, buf), r);
- }
- }
-}
-
-/**
- * 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.
- *
- * Locking: takes tty_ldisc_lock.
- * called functions take termios_mutex
- */
-
-static int tty_set_ldisc(struct tty_struct *tty, int ldisc)
-{
- int retval;
- struct tty_ldisc o_ldisc, new_ldisc;
- int work;
- unsigned long flags;
- struct tty_struct *o_tty;
-
-restart:
- /* This is a bit ugly for now but means we can break the 'ldisc
- is part of the tty struct' assumption later */
- retval = tty_ldisc_get(ldisc, &new_ldisc);
- if (retval)
- return retval;
-
- /*
- * Problem: What do we do if this blocks ?
- */
-
- tty_wait_until_sent(tty, 0);
-
- if (tty->ldisc.ops->num == ldisc) {
- tty_ldisc_put(new_ldisc.ops);
- return 0;
- }
-
- /*
- * 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;
- o_tty = tty->link;
-
- /*
- * 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.
- */
-
- spin_lock_irqsave(&tty_ldisc_lock, flags);
- if (tty->ldisc.refcount || (o_tty && o_tty->ldisc.refcount)) {
- if (tty->ldisc.refcount) {
- /* Free the new ldisc we grabbed. Must drop the lock
- first. */
- spin_unlock_irqrestore(&tty_ldisc_lock, flags);
- tty_ldisc_put(o_ldisc.ops);
- /*
- * There are several reasons we may be busy, including
- * random momentary I/O traffic. We must therefore
- * retry. We could distinguish between blocking ops
- * and retries if we made tty_ldisc_wait() smarter.
- * That is up for discussion.
- */
- if (wait_event_interruptible(tty_ldisc_wait, tty->ldisc.refcount == 0) < 0)
- return -ERESTARTSYS;
- goto restart;
- }
- if (o_tty && o_tty->ldisc.refcount) {
- spin_unlock_irqrestore(&tty_ldisc_lock, flags);
- tty_ldisc_put(o_tty->ldisc.ops);
- if (wait_event_interruptible(tty_ldisc_wait, o_tty->ldisc.refcount == 0) < 0)
- return -ERESTARTSYS;
- goto restart;
- }
- }
- /*
- * If the TTY_LDISC bit is set, then we are racing against
- * another ldisc change
- */
- if (!test_bit(TTY_LDISC, &tty->flags)) {
- struct tty_ldisc *ld;
- spin_unlock_irqrestore(&tty_ldisc_lock, flags);
- tty_ldisc_put(new_ldisc.ops);
- ld = tty_ldisc_ref_wait(tty);
- tty_ldisc_deref(ld);
- goto restart;
- }
-
- clear_bit(TTY_LDISC, &tty->flags);
- if (o_tty)
- clear_bit(TTY_LDISC, &o_tty->flags);
- spin_unlock_irqrestore(&tty_ldisc_lock, flags);
-
- /*
- * From this point on we know nobody has an ldisc
- * usage reference, nor can they obtain one until
- * we say so later on.
- */
-
- work = cancel_delayed_work(&tty->buf.work);
- /*
- * Wait for ->hangup_work and ->buf.work handlers to terminate
- * MUST NOT hold locks here.
- */
- flush_scheduled_work();
- /* Shutdown the current discipline. */
- if (o_ldisc.ops->close)
- (o_ldisc.ops->close)(tty);
-
- /* Now set up the new line discipline. */
- tty_ldisc_assign(tty, &new_ldisc);
- tty_set_termios_ldisc(tty, ldisc);
- if (new_ldisc.ops->open)
- retval = (new_ldisc.ops->open)(tty);
- if (retval < 0) {
- tty_ldisc_put(new_ldisc.ops);
- 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.ops);
-
- /*
- * Allow ldisc referencing to occur as soon as the driver
- * ldisc callback completes.
- */
-
- tty_ldisc_enable(tty);
- if (o_tty)
- tty_ldisc_enable(o_tty);
-
- /* Restart it in case no characters kick it off. Safe if
- already running */
- if (work)
- schedule_delayed_work(&tty->buf.work, 1);
- return retval;
-}
-
-/**
* get_tty_driver - find device of a tty
* @dev_t: device identifier
* @index: returns the index of the tty
@@ -2193,7 +1641,6 @@
struct ktermios *tp, **tp_loc, *o_tp, **o_tp_loc;
struct ktermios *ltp, **ltp_loc, *o_ltp, **o_ltp_loc;
int retval = 0;
- struct tty_ldisc *ld;
/* check whether we're reopening an existing tty */
if (driver->flags & TTY_DRIVER_DEVPTS_MEM) {
@@ -2342,25 +1789,12 @@
* If we fail here just call release_tty to clean up. No need
* to decrement the use counts, as release_tty doesn't care.
*/
-
- ld = &tty->ldisc;
- if (ld->ops->open) {
- retval = (ld->ops->open)(tty);
- if (retval)
- goto release_mem_out;
- }
- if (o_tty && o_tty->ldisc.ops->open) {
- retval = (o_tty->ldisc.ops->open)(o_tty);
- if (retval) {
- if (ld->ops->close)
- (ld->ops->close)(tty);
- goto release_mem_out;
- }
- tty_ldisc_enable(o_tty);
- }
- tty_ldisc_enable(tty);
- goto success;
+ retval = tty_ldisc_setup(tty, o_tty);
+
+ if (retval)
+ goto release_mem_out;
+ goto success;
/*
* This fast open can be used if the tty is already open.
@@ -2498,12 +1932,10 @@
static void release_dev(struct file *filp)
{
struct tty_struct *tty, *o_tty;
- struct tty_ldisc ld;
int pty_master, tty_closing, o_tty_closing, do_sleep;
int devpts;
int idx;
char buf[64];
- unsigned long flags;
tty = (struct tty_struct *)filp->private_data;
if (tty_paranoia_check(tty, filp->f_path.dentry->d_inode,
@@ -2705,56 +2137,9 @@
printk(KERN_DEBUG "freeing tty structure...");
#endif
/*
- * 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.
+ * Ask the line discipline code to release its structures
*/
- clear_bit(TTY_LDISC, &tty->flags);
- cancel_delayed_work(&tty->buf.work);
-
- /*
- * Wait for ->hangup_work and ->buf.work handlers to terminate
- */
-
- flush_scheduled_work();
-
- /*
- * Wait for any short term users (we know they are just driver
- * side waiters as the file is closing so user count on the file
- * side is zero.
- */
- spin_lock_irqsave(&tty_ldisc_lock, flags);
- while (tty->ldisc.refcount) {
- spin_unlock_irqrestore(&tty_ldisc_lock, flags);
- wait_event(tty_ldisc_wait, tty->ldisc.refcount == 0);
- spin_lock_irqsave(&tty_ldisc_lock, flags);
- }
- spin_unlock_irqrestore(&tty_ldisc_lock, flags);
- /*
- * Shutdown the current line discipline, and reset it to N_TTY.
- *
- * FIXME: this MUST get fixed for the new reflocking
- */
- if (tty->ldisc.ops->close)
- (tty->ldisc.ops->close)(tty);
- tty_ldisc_put(tty->ldisc.ops);
-
- /*
- * Switch the line discipline back
- */
- WARN_ON(tty_ldisc_get(N_TTY, &ld));
- tty_ldisc_assign(tty, &ld);
- tty_set_termios_ldisc(tty, N_TTY);
- if (o_tty) {
- /* FIXME: could o_tty be in setldisc here ? */
- clear_bit(TTY_LDISC, &o_tty->flags);
- if (o_tty->ldisc.ops->close)
- (o_tty->ldisc.ops->close)(o_tty);
- tty_ldisc_put(o_tty->ldisc.ops);
- WARN_ON(tty_ldisc_get(N_TTY, &ld));
- tty_ldisc_assign(o_tty, &ld);
- tty_set_termios_ldisc(o_tty, N_TTY);
- }
+ tty_ldisc_release(tty, o_tty);
/*
* The release_tty function takes care of the details of clearing
* the slots and preserving the termios structure.
@@ -3962,12 +3347,9 @@
static void initialize_tty_struct(struct tty_struct *tty)
{
- struct tty_ldisc ld;
memset(tty, 0, sizeof(struct tty_struct));
tty->magic = TTY_MAGIC;
- if (tty_ldisc_get(N_TTY, &ld) < 0)
- panic("n_tty: init_tty");
- tty_ldisc_assign(tty, &ld);
+ tty_ldisc_init(tty);
tty->session = NULL;
tty->pgrp = NULL;
tty->overrun_time = jiffies;
@@ -4280,7 +3662,7 @@
initcall_t *call;
/* Setup the default TTY line discipline. */
- (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY);
+ tty_ldisc_begin();
/*
* set up the console device so that later boot sequences can