On Fri, 2007-05-04 at 17:30 -0600, Paul Fulghum wrote:
> OK, this behavior is so unexpected I must be missing
> something basic.

And so I was. Try this patch.

--- a/drivers/char/tty_io.c     2007-05-04 05:46:55.000000000 -0500
+++ b/drivers/char/tty_io.c     2007-05-05 03:23:46.000000000 -0500
@@ -365,6 +365,29 @@ static void tty_buffer_free(struct tty_s
 }
 
 /**
+ *     tty_buffer_flush                -       flush full tty buffers
+ *     @tty: tty to flush
+ *
+ *     flush all the buffers containing receive data
+ *
+ *     Locking: none
+ */
+
+static void tty_buffer_flush(struct tty_struct *tty)
+{
+       struct tty_buffer *thead;
+       unsigned long flags;
+
+       spin_lock_irqsave(&tty->buf.lock, flags);
+       while((thead = tty->buf.head) != NULL) {
+               tty->buf.head = thead->next;
+               tty_buffer_free(tty, thead);
+       }
+       tty->buf.tail = NULL;
+       spin_unlock_irqrestore(&tty->buf.lock, flags);
+}
+
+/**
  *     tty_buffer_find         -       find a free tty buffer
  *     @tty: tty owning the buffer
  *     @size: characters wanted
@@ -1240,6 +1263,7 @@ void tty_ldisc_flush(struct tty_struct *
                        ld->flush_buffer(tty);
                tty_ldisc_deref(ld);
        }
+       tty_buffer_flush(tty);
 }
 
 EXPORT_SYMBOL_GPL(tty_ldisc_flush);
@@ -3336,6 +3360,15 @@ int tty_ioctl(struct inode * inode, stru
                case TIOCMBIC:
                case TIOCMBIS:
                        return tty_tiocmset(tty, file, cmd, p);
+               case TCFLSH:
+                       switch (arg) {
+                       case TCIFLUSH:
+                       case TCIOFLUSH:
+                               /* flush tty buffer and allow ldisc to process 
ioctl */
+                               tty_buffer_flush(tty);
+                               break;
+                       }
+                       break;
        }
        if (tty->driver->ioctl) {
                retval = (tty->driver->ioctl)(tty, file, cmd, arg);


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