tty: add throttle/unthrottle helpers

Something Arjan suggested which allows us to clean up the code nicely

Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

9 files changed, 31 insertions, 25 deletions

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index a6c2619ec782..e5cd856a2fea 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -370,9 +370,7 @@ static void hci_uart_tty_receive(struct tty_struct *tty, const u8 *data, char *f
         hu->hdev->stat.byte_rx += count;
         spin_unlock(&hu->rx_lock);
 
-        if (test_and_clear_bit(TTY_THROTTLED, &tty->flags) &&
-                                        tty->ops->unthrottle)
-                tty->ops->unthrottle(tty);
+        tty_unthrottle(tty);
 }
 
 static int hci_uart_register_dev(struct hci_uart *hu)
diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c
index abc93a93dcdd..19105ec203f7 100644
--- a/drivers/char/n_tty.c
+++ b/drivers/char/n_tty.c
@@ -147,10 +147,8 @@ static void put_tty_queue(unsigned char c, struct tty_struct *tty)
 
 static void check_unthrottle(struct tty_struct *tty)
 {
-        if (tty->count &&
-            test_and_clear_bit(TTY_THROTTLED, &tty->flags) &&
-            tty->ops->unthrottle)
-                tty->ops->unthrottle(tty);
+        if (tty->count)
+                tty_unthrottle(tty);
 }
 
 /**
@@ -982,12 +980,8 @@ static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
          * mode.  We don't want to throttle the driver if we're in
          * canonical mode and don't have a newline yet!
          */
-        if (tty->receive_room < TTY_THRESHOLD_THROTTLE) {
-                /* check TTY_THROTTLED first so it indicates our state */
-                if (!test_and_set_bit(TTY_THROTTLED, &tty->flags) &&
-                    tty->ops->throttle)
-                        tty->ops->throttle(tty);
-        }
+        if (tty->receive_room < TTY_THRESHOLD_THROTTLE)
+                tty_throttle(tty);
 }
 
 int is_ignored(int sig)
diff --git a/drivers/char/tty_ioctl.c b/drivers/char/tty_ioctl.c
index c10d40c4c5ca..b1a757a5ee27 100644
--- a/drivers/char/tty_ioctl.c
+++ b/drivers/char/tty_ioctl.c
@@ -67,6 +67,22 @@ void tty_driver_flush_buffer(struct tty_struct *tty)
 
 EXPORT_SYMBOL(tty_driver_flush_buffer);
 
+void tty_throttle(struct tty_struct *tty)
+{
+        /* check TTY_THROTTLED first so it indicates our state */
+        if (!test_and_set_bit(TTY_THROTTLED, &tty->flags) &&
+            tty->ops->throttle)
+                tty->ops->throttle(tty);
+}
+EXPORT_SYMBOL(tty_throttle);
+
+void tty_unthrottle(struct tty_struct *tty)
+{
+        if (test_and_clear_bit(TTY_THROTTLED, &tty->flags) &&
+            tty->ops->unthrottle)
+                tty->ops->unthrottle(tty);
+}
+EXPORT_SYMBOL(tty_unthrottle);
 
 /**
  *      tty_wait_until_sent     -       wait for I/O to finish
diff --git a/drivers/net/hamradio/6pack.c b/drivers/net/hamradio/6pack.c
index 82a36266dfc9..9d5721287d6f 100644
--- a/drivers/net/hamradio/6pack.c
+++ b/drivers/net/hamradio/6pack.c
@@ -491,9 +491,7 @@ static void sixpack_receive_buf(struct tty_struct *tty,
         sixpack_decode(sp, buf, count1);
 
         sp_put(sp);
-        if (test_and_clear_bit(TTY_THROTTLED, &tty->flags)
-            && tty->ops->unthrottle)
-                tty->ops->unthrottle(tty);
+        tty_unthrottle(tty);
 }
 
 /*
diff --git a/drivers/net/hamradio/mkiss.c b/drivers/net/hamradio/mkiss.c
index ebcc5adee7cc..65166035aca0 100644
--- a/drivers/net/hamradio/mkiss.c
+++ b/drivers/net/hamradio/mkiss.c
@@ -936,9 +936,7 @@ static void mkiss_receive_buf(struct tty_struct *tty, const unsigned char *cp,
         }
 
         mkiss_put(ax);
-        if (test_and_clear_bit(TTY_THROTTLED, &tty->flags)
-            && tty->ops->unthrottle)
-                tty->ops->unthrottle(tty);
+        tty_unthrottle(tty);
 }
 
 /*
diff --git a/drivers/net/ppp_async.c b/drivers/net/ppp_async.c
index 1c4b7e37912c..f1a52def1241 100644
--- a/drivers/net/ppp_async.c
+++ b/drivers/net/ppp_async.c
@@ -361,9 +361,7 @@ ppp_asynctty_receive(struct tty_struct *tty, const unsigned char *buf,
         if (!skb_queue_empty(&ap->rqueue))
                 tasklet_schedule(&ap->tsk);
         ap_put(ap);
-        if (test_and_clear_bit(TTY_THROTTLED, &tty->flags)
-            && tty->ops->unthrottle)
-                tty->ops->unthrottle(tty);
+        tty_unthrottle(tty);
 }
 
 static void
diff --git a/drivers/net/ppp_synctty.c b/drivers/net/ppp_synctty.c
index 48ed5fdbfe18..b8f0369a71e7 100644
--- a/drivers/net/ppp_synctty.c
+++ b/drivers/net/ppp_synctty.c
@@ -401,9 +401,7 @@ ppp_sync_receive(struct tty_struct *tty, const unsigned char *buf,
         if (!skb_queue_empty(&ap->rqueue))
                 tasklet_schedule(&ap->tsk);
         sp_put(ap);
-        if (test_and_clear_bit(TTY_THROTTLED, &tty->flags)
-            && tty->ops->unthrottle)
-                tty->ops->unthrottle(tty);
+        tty_unthrottle(tty);
 }
 
 static void
diff --git a/include/linux/tty.h b/include/linux/tty.h
index c36a76da2ae2..7f7121f9c968 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -303,6 +303,8 @@ extern int tty_put_char(struct tty_struct *tty, unsigned char c);
 extern int tty_chars_in_buffer(struct tty_struct *tty);
 extern int tty_write_room(struct tty_struct *tty);
 extern void tty_driver_flush_buffer(struct tty_struct *tty);
+extern void tty_throttle(struct tty_struct *tty);
+extern void tty_unthrottle(struct tty_struct *tty);
 
 extern int is_current_pgrp_orphaned(void);
 extern struct pid *tty_get_pgrp(struct tty_struct *tty);
diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h
index f80d73b690f6..59f1c0bd8f9c 100644
--- a/include/linux/tty_driver.h
+++ b/include/linux/tty_driver.h
@@ -100,6 +100,8 @@
  *      This routine notifies the tty driver that input buffers for
  *      the line discipline are close to full, and it should somehow
  *      signal that no more characters should be sent to the tty.
+ *
+ *      Optional: Always invoke via tty_throttle();
  * 
  * void (*unthrottle)(struct tty_struct * tty);
  *
@@ -107,6 +109,8 @@
  *      that characters can now be sent to the tty without fear of
  *      overrunning the input buffers of the line disciplines.
  * 
+ *      Optional: Always invoke via tty_unthrottle();
+ *
  * void (*stop)(struct tty_struct *tty);
  *
  *      This routine notifies the tty driver that it should stop