tty: Enable configurable tty flip buffer limit
Allow driver to configure its maximum flip buffer memory
consumption/limit. This is necessary for very-high speed line
rates (in excess of 10MB/sec) because the flip buffers can
be saturated before the line discipline has a chance to
throttle the input.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
index c043136f..57eb34b 100644
--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c
@@ -26,7 +26,7 @@
* Byte threshold to limit memory consumption for flip buffers.
* The actual memory limit is > 2x this amount.
*/
-#define TTYB_MEM_LIMIT 65536
+#define TTYB_DEFAULT_MEM_LIMIT 65536
/*
* We default to dicing tty buffer allocations to this many characters
@@ -89,7 +89,7 @@
int tty_buffer_space_avail(struct tty_port *port)
{
- int space = TTYB_MEM_LIMIT - atomic_read(&port->buf.memory_used);
+ int space = port->buf.mem_limit - atomic_read(&port->buf.memory_used);
return max(space, 0);
}
@@ -162,7 +162,7 @@
/* Should possibly check if this fails for the largest buffer we
have queued and recycle that ? */
- if (atomic_read(&port->buf.memory_used) > TTYB_MEM_LIMIT)
+ if (atomic_read(&port->buf.memory_used) > port->buf.mem_limit)
return NULL;
p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC);
if (p == NULL)
@@ -536,4 +536,22 @@
atomic_set(&buf->memory_used, 0);
atomic_set(&buf->priority, 0);
INIT_WORK(&buf->work, flush_to_ldisc);
+ buf->mem_limit = TTYB_DEFAULT_MEM_LIMIT;
}
+
+/**
+ * tty_buffer_set_limit - change the tty buffer memory limit
+ * @port: tty port to change
+ *
+ * Change the tty buffer memory limit.
+ * Must be called before the other tty buffer functions are used.
+ */
+
+int tty_buffer_set_limit(struct tty_port *port, int limit)
+{
+ if (limit < MIN_TTYB_SIZE)
+ return -EINVAL;
+ port->buf.mem_limit = limit;
+ return 0;
+}
+EXPORT_SYMBOL_GPL(tty_buffer_set_limit);