tty: Track flip buffer memory limit atomically
Lockless flip buffers require atomically updating the bytes-in-use
watermark.
The pty driver also peeks at the watermark value to limit
memory consumption to a much lower value than the default; query
the watermark with new fn, tty_buffer_space_avail().
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/include/linux/tty_flip.h b/include/linux/tty_flip.h
index ad03039..6944ed2 100644
--- a/include/linux/tty_flip.h
+++ b/include/linux/tty_flip.h
@@ -1,6 +1,7 @@
#ifndef _LINUX_TTY_FLIP_H
#define _LINUX_TTY_FLIP_H
+extern int tty_buffer_space_avail(struct tty_port *port);
extern int tty_buffer_request_room(struct tty_port *port, size_t size);
extern int tty_insert_flip_string_flags(struct tty_port *port,
const unsigned char *chars, const char *flags, size_t size);