diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c
index acd76b767d4c10aac5b540e31a1cd2dddf3c8436..1733d3439ad2fd31e2cac8d083c5de499c4a685d 100644
--- a/drivers/char/tty_ldisc.c
+++ b/drivers/char/tty_ldisc.c
@@ -48,6 +48,41 @@ static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait);
/* 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
@@ -142,7 +177,7 @@ static struct tty_ldisc *tty_ldisc_try_get(int disc)
/* lock it */
ldops->refcount++;
ld->ops = ldops;
- ld->refcount = 0;
+ atomic_set(&ld->users, 1);
err = 0;
}
}
@@ -181,35 +216,6 @@ static struct tty_ldisc *tty_ldisc_get(int disc)
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);
-
- 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(ld->refcount);
- kfree(ld);
-}
-
static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos)
{
return (*pos < NR_LDISCS) ? pos : NULL;
@@ -234,7 +240,7 @@ static int tty_ldiscs_seq_show(struct seq_file *m, void *v)
if (IS_ERR(ld))
return 0;
seq_printf(m, "%-10s %2d\n", ld->ops->name ? ld->ops->name : "???", i);
- tty_ldisc_put(ld);
+ put_ldisc(ld);
return 0;
}
@@ -288,20 +294,17 @@ static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld)
* 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)) {
- ld->refcount++;
- 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;
}
/**
@@ -322,10 +325,11 @@ static int tty_ldisc_try(struct tty_struct *tty)
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(tty->ldisc->refcount == 0);
- return tty->ldisc;
+ wait_event(tty_ldisc_wait, (ld = tty_ldisc_try(tty)) != NULL);
+ return ld;
}
EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);
@@ -342,9 +346,7 @@ 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);
@@ -360,21 +362,15 @@ 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 (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);
+ 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
@@ -522,31 +518,6 @@ static int tty_ldisc_halt(struct tty_struct *tty)
return cancel_delayed_work(&tty->buf.work);
}
-/**
- * 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 (tty->ldisc->refcount) {
- spin_unlock_irqrestore(&tty_ldisc_lock, flags);
- if (wait_event_timeout(tty_ldisc_wait,
- tty->ldisc->refcount == 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
@@ -642,14 +613,6 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
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
@@ -795,7 +758,6 @@ void tty_ldisc_hangup(struct tty_struct *tty)
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
@@ -860,14 +822,6 @@ void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
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
diff --git a/include/linux/tty_ldisc.h b/include/linux/tty_ldisc.h
index 40f38d896777400f1bcbb56c36063eed22db45fe..0c4ee9b88f8551d51c308840a7f3c7ba7fb83d13 100644
--- a/include/linux/tty_ldisc.h
+++ b/include/linux/tty_ldisc.h
@@ -144,7 +144,7 @@ struct tty_ldisc_ops {
struct tty_ldisc {
struct tty_ldisc_ops *ops;
- int refcount;
+ atomic_t users;
};
#define TTY_LDISC_MAGIC 0x5403