[PATCH] uml: Add throttling to console driver

This patch adds support for throttling and unthrottling input when the tty
driver can't handle it.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 27 insertions, 2 deletions

diff --git a/arch/um/drivers/line.c b/arch/um/drivers/line.c
index 851a7c8caae5..b8e3e800ee41 100644
--- a/arch/um/drivers/line.c
+++ b/arch/um/drivers/line.c
@@ -36,8 +36,9 @@ static void line_timer_cb(void *arg)
 {
         struct line *line = arg;
 
-        chan_interrupt(&line->chan_list, &line->task, line->tty,
-                       line->driver->read_irq);
+        if(!line->throttled)
+                chan_interrupt(&line->chan_list, &line->task, line->tty,
+                               line->driver->read_irq);
 }
 
 /* Returns the free space inside the ring buffer of this line.
@@ -340,6 +341,30 @@ int line_ioctl(struct tty_struct *tty, struct file * file,
         return ret;
 }
 
+void line_throttle(struct tty_struct *tty)
+{
+        struct line *line = tty->driver_data;
+
+        deactivate_chan(&line->chan_list, line->driver->read_irq);
+        line->throttled = 1;
+}
+
+void line_unthrottle(struct tty_struct *tty)
+{
+        struct line *line = tty->driver_data;
+
+        line->throttled = 0;
+        chan_interrupt(&line->chan_list, &line->task, tty,
+                       line->driver->read_irq);
+
+        /* Maybe there is enough stuff pending that calling the interrupt
+         * throttles us again.  In this case, line->throttled will be 1
+         * again and we shouldn't turn the interrupt back on.
+         */
+        if(!line->throttled)
+                reactivate_chan(&line->chan_list, line->driver->read_irq);
+}
+
 static irqreturn_t line_write_interrupt(int irq, void *data,
                                         struct pt_regs *unused)
 {