tty_buffer_request_room is well protected, but while after it returns, it releases the port->lock. tty->buf.tail might be modified by either irq handler or other threads. The patch adds more protection by holding the lock across tty buffer finding and buffer filling. Signed-off-by: Alek Du <alek.du@intel.com> Signed-off-by: Xiaobing Tu <xiaobing.tu@intel.com> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Change-Id: I7561321a1e78c9730232f98085e01fc1749a48f5 CRs-Fixed: 387308 Signed-off-by: Vamsi Krishna <vskrishn@codeaurora.org>