| From 7842055bfce4bf0170d0f61df8b2add8399697be Mon Sep 17 00:00:00 2001 |
| From: Ulrich Hecht <ulrich.hecht+renesas@gmail.com> |
| Date: Thu, 15 Feb 2018 13:02:27 +0100 |
| Subject: serial: sh-sci: prevent lockup on full TTY buffers |
| |
| From: Ulrich Hecht <ulrich.hecht+renesas@gmail.com> |
| |
| commit 7842055bfce4bf0170d0f61df8b2add8399697be upstream. |
| |
| When the TTY buffers fill up to the configured maximum, a system lockup |
| occurs: |
| |
| [ 598.820128] INFO: rcu_preempt detected stalls on CPUs/tasks: |
| [ 598.825796] 0-...!: (1 GPs behind) idle=5a6/2/0 softirq=1974/1974 fqs=1 |
| [ 598.832577] (detected by 3, t=62517 jiffies, g=296, c=295, q=126) |
| [ 598.838755] Task dump for CPU 0: |
| [ 598.841977] swapper/0 R running task 0 0 0 0x00000022 |
| [ 598.849023] Call trace: |
| [ 598.851476] __switch_to+0x98/0xb0 |
| [ 598.854870] (null) |
| |
| This can be prevented by doing a dummy read of the RX data register. |
| |
| This issue affects both HSCIF and SCIF ports. Reported for R-Car H3 ES2.0; |
| reproduced and fixed on H3 ES1.1. Probably affects other R-Car platforms |
| as well. |
| |
| Reported-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com> |
| Signed-off-by: Ulrich Hecht <ulrich.hecht+renesas@gmail.com> |
| Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be> |
| Cc: stable <stable@vger.kernel.org> |
| Tested-by: Nguyen Viet Dung <dung.nguyen.aj@renesas.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| drivers/tty/serial/sh-sci.c | 2 ++ |
| 1 file changed, 2 insertions(+) |
| |
| --- a/drivers/tty/serial/sh-sci.c |
| +++ b/drivers/tty/serial/sh-sci.c |
| @@ -886,6 +886,8 @@ static void sci_receive_chars(struct uar |
| /* Tell the rest of the system the news. New characters! */ |
| tty_flip_buffer_push(tport); |
| } else { |
| + /* TTY buffers full; read from RX reg to prevent lockup */ |
| + serial_port_in(port, SCxRDR); |
| serial_port_in(port, SCxSR); /* dummy read */ |
| sci_clear_SCxSR(port, SCxSR_RDxF_CLEAR(port)); |
| } |