[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>

6 files changed, 63 insertions, 14 deletions

diff --git a/arch/um/drivers/chan_kern.c b/arch/um/drivers/chan_kern.c
index 36df55ad64c2..cd13b91b9ff6 100644
--- a/arch/um/drivers/chan_kern.c
+++ b/arch/um/drivers/chan_kern.c
@@ -312,6 +312,32 @@ void close_chan(struct list_head *chans, int delay_free_irq)
         }
 }
 
+void deactivate_chan(struct list_head *chans, int irq)
+{
+        struct list_head *ele;
+
+        struct chan *chan;
+        list_for_each(ele, chans) {
+                chan = list_entry(ele, struct chan, list);
+
+                if(chan->enabled && chan->input)
+                        deactivate_fd(chan->fd, irq);
+        }
+}
+
+void reactivate_chan(struct list_head *chans, int irq)
+{
+        struct list_head *ele;
+        struct chan *chan;
+
+        list_for_each(ele, chans) {
+                chan = list_entry(ele, struct chan, list);
+
+                if(chan->enabled && chan->input)
+                        reactivate_fd(chan->fd, irq);
+        }
+}
+
 int write_chan(struct list_head *chans, const char *buf, int len,
                int write_irq)
 {
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)
 {
diff --git a/arch/um/drivers/ssl.c b/arch/um/drivers/ssl.c
index 6823dc5d665c..a32ef55cb244 100644
--- a/arch/um/drivers/ssl.c
+++ b/arch/um/drivers/ssl.c
@@ -109,16 +109,6 @@ static void ssl_flush_buffer(struct tty_struct *tty)
         return;
 }
 
-static void ssl_throttle(struct tty_struct * tty)
-{
-        printk(KERN_ERR "Someone should implement ssl_throttle\n");
-}
-
-static void ssl_unthrottle(struct tty_struct * tty)
-{
-        printk(KERN_ERR "Someone should implement ssl_unthrottle\n");
-}
-
 static void ssl_stop(struct tty_struct *tty)
 {
         printk(KERN_ERR "Someone should implement ssl_stop\n");
@@ -145,9 +135,9 @@ static struct tty_operations ssl_ops = {
         .flush_chars            = line_flush_chars,
         .set_termios            = line_set_termios,
         .ioctl                  = line_ioctl,
+        .throttle               = line_throttle,
+        .unthrottle             = line_unthrottle,
 #if 0
-        .throttle               = ssl_throttle,
-        .unthrottle             = ssl_unthrottle,
         .stop                   = ssl_stop,
         .start                  = ssl_start,
         .hangup                 = ssl_hangup,
diff --git a/arch/um/drivers/stdio_console.c b/arch/um/drivers/stdio_console.c
index 6d4edda9b510..61db8b2fc83f 100644
--- a/arch/um/drivers/stdio_console.c
+++ b/arch/um/drivers/stdio_console.c
@@ -122,6 +122,8 @@ static struct tty_operations console_ops = {
         .flush_chars            = line_flush_chars,
         .set_termios            = line_set_termios,
         .ioctl                  = line_ioctl,
+        .throttle               = line_throttle,
+        .unthrottle             = line_unthrottle,
 };
 
 static void uml_console_write(struct console *console, const char *string,
diff --git a/arch/um/include/chan_kern.h b/arch/um/include/chan_kern.h
index 84d1f64f9795..1bb5e9d94270 100644
--- a/arch/um/include/chan_kern.h
+++ b/arch/um/include/chan_kern.h
@@ -38,6 +38,8 @@ extern int console_write_chan(struct list_head *chans, const char *buf,
                               int len);
 extern int console_open_chan(struct line *line, struct console *co,
                              struct chan_opts *opts);
+extern void deactivate_chan(struct list_head *chans, int irq);
+extern void reactivate_chan(struct list_head *chans, int irq);
 extern void chan_enable_winch(struct list_head *chans, struct tty_struct *tty);
 extern void enable_chan(struct line *line);
 extern void close_chan(struct list_head *chans, int delay_free_irq);
diff --git a/arch/um/include/line.h b/arch/um/include/line.h
index e6cc3abfd4db..6f4d680dc1d4 100644
--- a/arch/um/include/line.h
+++ b/arch/um/include/line.h
@@ -38,6 +38,7 @@ struct line {
         struct list_head chan_list;
         int valid;
         int count;
+        int throttled;
         /*This lock is actually, mostly, local to*/
         spinlock_t lock;
 
@@ -60,6 +61,7 @@ struct line {
         { init_str :    str, \
           init_pri :    INIT_STATIC, \
           valid :       1, \
+          throttled :   0, \
           lock :        SPIN_LOCK_UNLOCKED, \
           buffer :      NULL, \
           head :        NULL, \
@@ -88,6 +90,8 @@ extern void line_flush_chars(struct tty_struct *tty);
 extern int line_write_room(struct tty_struct *tty);
 extern int line_ioctl(struct tty_struct *tty, struct file * file,
                       unsigned int cmd, unsigned long arg);
+extern void line_throttle(struct tty_struct *tty);
+extern void line_unthrottle(struct tty_struct *tty);
 
 extern char *add_xterm_umid(char *base);
 extern int line_setup_irq(int fd, int input, int output, struct line *line,