serial_core: Update buffer overrun statistics.

Currently, serial drivers don't report buffer overruns. When a buffer overrun
occurs, tty_insert_flip_char returns 0, and no attempt is made to insert that
same character again (i.e. it is lost). This patch reports buffer overruns via
the buf_overrun field in the port's icount structure.

Signed-off-by: Corbin Atkinson <corbin.atkinson@xxxxxx>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 246b823c1b27..a21dc8e3b7c0 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2527,14 +2527,16 @@ void uart_insert_char(struct uart_port *port, unsigned int status,
         struct tty_struct *tty = port->state->port.tty;
 
         if ((status & port->ignore_status_mask & ~overrun) == 0)
-                tty_insert_flip_char(tty, ch, flag);
+                if (tty_insert_flip_char(tty, ch, flag) == 0)
+                        ++port->icount.buf_overrun;
 
         /*
          * Overrun is special.  Since it's reported immediately,
          * it doesn't affect the current character.
          */
         if (status & ~port->ignore_status_mask & overrun)
-                tty_insert_flip_char(tty, 0, TTY_OVERRUN);
+                if (tty_insert_flip_char(tty, 0, TTY_OVERRUN) == 0)
+                        ++port->icount.buf_overrun;
 }
 EXPORT_SYMBOL_GPL(uart_insert_char);