This is a note to let you know that I've just added the patch titled
serial: sh-sci: prevent lockup on full TTY buffers
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
serial-sh-sci-prevent-lockup-on-full-tty-buffers.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 7842055bfce4bf0170d0f61df8b2add8399697be Mon Sep 17 00:00:00 2001
From: Ulrich Hecht <ulrich.hecht+renesas@xxxxxxxxx>
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@xxxxxxxxx>
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@xxxxxxxxxxx>
Signed-off-by: Ulrich Hecht <ulrich.hecht+renesas@xxxxxxxxx>
Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx>
Tested-by: Nguyen Viet Dung <dung.nguyen.aj@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
@@ -847,6 +847,8 @@ 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));
}
Patches currently in stable-queue which might be from ulrich.hecht+renesas@xxxxxxxxx are
queue-4.4/serial-sh-sci-prevent-lockup-on-full-tty-buffers.patch