/* Line disc dispatch table */
static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS];
+static inline struct tty_ldisc *get_ldisc(struct tty_ldisc *ld)
+{
+ if (ld)
+ atomic_inc(&ld->users);
+ return ld;
+}
+
+static void put_ldisc(struct tty_ldisc *ld)
+{
+ unsigned long flags;
+
+ if (WARN_ON_ONCE(!ld))
+ return;
+
+ /*
+ * If this is the last user, free the ldisc, and
+ * release the ldisc ops.
+ *
+ * We really want an "atomic_dec_and_lock_irqsave()",
+ * but we don't have it, so this does it by hand.
+ */
+ local_irq_save(flags);
+ if (atomic_dec_and_lock(&ld->users, &tty_ldisc_lock)) {
+ struct tty_ldisc_ops *ldo = ld->ops;
+
+ ldo->refcount--;
+ module_put(ldo->owner);
+ spin_unlock_irqrestore(&tty_ldisc_lock, flags);
+
+ kfree(ld);
+ return;
+ }
+ local_irq_restore(flags);
+}
+
/**
* tty_register_ldisc - install a line discipline
* @disc: ldisc number
}
EXPORT_SYMBOL(tty_unregister_ldisc);
-
-/**
- * tty_ldisc_try_get - try and reference an ldisc
- * @disc: ldisc number
- *
- * Attempt to open and lock a line discipline into place. Return
- * the line discipline refcounted or an error.
- */
-
-static struct tty_ldisc *tty_ldisc_try_get(int disc)
+static struct tty_ldisc_ops *get_ldops(int disc)
{
unsigned long flags;
- struct tty_ldisc *ld;
- struct tty_ldisc_ops *ldops;
- int err = -EINVAL;
-
- ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL);
- if (ld == NULL)
- return ERR_PTR(-ENOMEM);
+ struct tty_ldisc_ops *ldops, *ret;
spin_lock_irqsave(&tty_ldisc_lock, flags);
- ld->ops = NULL;
+ ret = ERR_PTR(-EINVAL);
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 */
+ ret = ERR_PTR(-EAGAIN);
+ if (try_module_get(ldops->owner)) {
ldops->refcount++;
- ld->ops = ldops;
- atomic_set(&ld->users, 0);
- err = 0;
+ ret = ldops;
}
}
spin_unlock_irqrestore(&tty_ldisc_lock, flags);
- if (err) {
- kfree(ld);
- return ERR_PTR(err);
- }
- return ld;
+ return ret;
+}
+
+static void put_ldops(struct tty_ldisc_ops *ldops)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&tty_ldisc_lock, flags);
+ ldops->refcount--;
+ module_put(ldops->owner);
+ spin_unlock_irqrestore(&tty_ldisc_lock, flags);
}
/**
static struct tty_ldisc *tty_ldisc_get(int disc)
{
struct tty_ldisc *ld;
+ struct tty_ldisc_ops *ldops;
if (disc < N_TTY || disc >= NR_LDISCS)
return ERR_PTR(-EINVAL);
- ld = tty_ldisc_try_get(disc);
- if (IS_ERR(ld)) {
+
+ /*
+ * Get the ldisc ops - we may need to request them to be loaded
+ * dynamically and try again.
+ */
+ ldops = get_ldops(disc);
+ if (IS_ERR(ldops)) {
request_module("tty-ldisc-%d", disc);
- ld = tty_ldisc_try_get(disc);
+ ldops = get_ldops(disc);
+ if (IS_ERR(ldops))
+ return ERR_CAST(ldops);
}
- return ld;
-}
-
-/**
- * tty_ldisc_put - drop ldisc reference
- * @ld: ldisc
- *
- * Drop a reference to a line discipline. Manage refcounts and
- * module usage counts. Free the ldisc once the recount hits zero.
- *
- * Locking:
- * takes tty_ldisc_lock to guard against ldisc races
- */
-static void tty_ldisc_put(struct tty_ldisc *ld)
-{
- unsigned long flags;
- int disc = ld->ops->num;
- struct tty_ldisc_ops *ldo;
-
- BUG_ON(disc < N_TTY || disc >= NR_LDISCS);
+ ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL);
+ if (ld == NULL) {
+ put_ldops(ldops);
+ return ERR_PTR(-ENOMEM);
+ }
- spin_lock_irqsave(&tty_ldisc_lock, flags);
- ldo = tty_ldiscs[disc];
- BUG_ON(ldo->refcount == 0);
- ldo->refcount--;
- module_put(ldo->owner);
- spin_unlock_irqrestore(&tty_ldisc_lock, flags);
- WARN_ON(atomic_read(&ld->users));
- kfree(ld);
+ ld->ops = ldops;
+ atomic_set(&ld->users, 1);
+ return ld;
}
static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos)
static int tty_ldiscs_seq_show(struct seq_file *m, void *v)
{
int i = *(loff_t *)v;
- struct tty_ldisc *ld;
+ struct tty_ldisc_ops *ldops;
- ld = tty_ldisc_try_get(i);
- if (IS_ERR(ld))
+ ldops = get_ldops(i);
+ if (IS_ERR(ldops))
return 0;
- seq_printf(m, "%-10s %2d\n", ld->ops->name ? ld->ops->name : "???", i);
- tty_ldisc_put(ld);
+ seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i);
+ put_ldops(ldops);
return 0;
}
* Locking: takes tty_ldisc_lock
*/
-static int tty_ldisc_try(struct tty_struct *tty)
+static struct tty_ldisc *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)) {
- atomic_inc(&ld->users);
- ret = 1;
- }
+ ld = NULL;
+ if (test_bit(TTY_LDISC, &tty->flags))
+ ld = get_ldisc(tty->ldisc);
spin_unlock_irqrestore(&tty_ldisc_lock, flags);
- return ret;
+ return ld;
}
/**
struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
{
+ struct tty_ldisc *ld;
+
/* wait_event is a macro */
- wait_event(tty_ldisc_wait, tty_ldisc_try(tty));
- WARN_ON(atomic_read(&tty->ldisc->users) == 0);
- return tty->ldisc;
+ wait_event(tty_ldisc_wait, (ld = tty_ldisc_try(tty)) != NULL);
+ return ld;
}
EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);
struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty)
{
- if (tty_ldisc_try(tty))
- return tty->ldisc;
- return NULL;
+ return tty_ldisc_try(tty);
}
EXPORT_SYMBOL_GPL(tty_ldisc_ref);
void tty_ldisc_deref(struct tty_ldisc *ld)
{
- unsigned long flags;
-
- BUG_ON(ld == NULL);
-
- spin_lock_irqsave(&tty_ldisc_lock, flags);
- if (atomic_read(&ld->users) == 0)
- printk(KERN_ERR "tty_ldisc_deref: no references.\n");
- else if (atomic_dec_and_test(&ld->users))
- wake_up(&tty_ldisc_wait);
- spin_unlock_irqrestore(&tty_ldisc_lock, flags);
+ put_ldisc(ld);
}
EXPORT_SYMBOL_GPL(tty_ldisc_deref);
+static inline void tty_ldisc_put(struct tty_ldisc *ld)
+{
+ put_ldisc(ld);
+}
+
/**
* tty_ldisc_enable - allow ldisc use
* @tty: terminal to activate ldisc on
* be obtained while the delayed work queue halt ensures that no more
* data is fed to the ldisc.
*
- * In order to wait for any existing references to complete see
- * tty_ldisc_wait_idle.
+ * You need to do a 'flush_scheduled_work()' (outside the ldisc_mutex)
+ * in order to make sure any currently executing ldisc work is also
+ * flushed.
*/
static int tty_ldisc_halt(struct tty_struct *tty)
}
/**
- * tty_ldisc_wait_idle - wait for the ldisc to become idle
- * @tty: tty to wait for
- *
- * Wait for the line discipline to become idle. The discipline must
- * have been halted for this to guarantee it remains idle.
- *
- * tty_ldisc_lock protects the ref counts currently.
- */
-
-static int tty_ldisc_wait_idle(struct tty_struct *tty)
-{
- unsigned long flags;
- spin_lock_irqsave(&tty_ldisc_lock, flags);
- while (atomic_read(&tty->ldisc->users)) {
- spin_unlock_irqrestore(&tty_ldisc_lock, flags);
- if (wait_event_timeout(tty_ldisc_wait,
- atomic_read(&tty->ldisc->users) == 0, 5 * HZ) == 0)
- return -EBUSY;
- spin_lock_irqsave(&tty_ldisc_lock, flags);
- }
- spin_unlock_irqrestore(&tty_ldisc_lock, flags);
- return 0;
-}
-
-/**
* tty_set_ldisc - set line discipline
* @tty: the terminal to set
* @ldisc: the line discipline
flush_scheduled_work();
- /* Let any existing reference holders finish */
- retval = tty_ldisc_wait_idle(tty);
- if (retval < 0) {
- clear_bit(TTY_LDISC_CHANGING, &tty->flags);
- tty_ldisc_put(new_ldisc);
- return retval;
- }
-
mutex_lock(&tty->ldisc_mutex);
if (test_bit(TTY_HUPPED, &tty->flags)) {
/* We were raced by the hangup method. It will have stomped
* N_TTY.
*/
if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) {
+ /* Make sure the old ldisc is quiescent */
+ tty_ldisc_halt(tty);
+ flush_scheduled_work();
+
/* Avoid racing set_ldisc or tty_ldisc_release */
mutex_lock(&tty->ldisc_mutex);
if (tty->ldisc) { /* Not yet closed */
/* Switch back to N_TTY */
- tty_ldisc_halt(tty);
- tty_ldisc_wait_idle(tty);
tty_ldisc_reinit(tty);
/* At this point we have a closed ldisc and we want to
reopen it. We could defer this to the next open but
tty_ldisc_halt(tty);
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.
- */
-
- tty_ldisc_wait_idle(tty);
-
mutex_lock(&tty->ldisc_mutex);
/*
* Now kill off the ldisc
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff