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| author | Ulrich Hecht <ulrich.hecht+renesas@gmail.com> | 2018-02-15 13:02:27 +0100 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2018-06-01 00:30:19 +0100 |
| commit | 1063c9391c430f0059780c55be0874dce91e59d2 (patch) | |
| tree | ef0f56155c98b2065192d4ebf6c56dd2c234bfb0 | |
| parent | 50bf8fc9a9a95b1c97b79278177a2378f4c7d6ad (diff) | |
| download | linux-1063c9391c430f0059780c55be0874dce91e59d2.tar.gz linux-1063c9391c430f0059780c55be0874dce91e59d2.tar.bz2 linux-1063c9391c430f0059780c55be0874dce91e59d2.zip | |
serial: sh-sci: prevent lockup on full TTY buffers
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>
Tested-by: Nguyen Viet Dung <dung.nguyen.aj@renesas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2:
- Use sci_in()
- Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
| -rw-r--r-- | drivers/tty/serial/sh-sci.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c index 60f71ec60992..4b735250f10e 100644 --- a/drivers/tty/serial/sh-sci.c +++ b/drivers/tty/serial/sh-sci.c @@ -668,6 +668,8 @@ static void sci_receive_chars(struct uart_port *port) /* Tell the rest of the system the news. New characters! */ tty_flip_buffer_push(tty); } else { + /* TTY buffers full; read from RX reg to prevent lockup */ + sci_in(port, SCxRDR); sci_in(port, SCxSR); /* dummy read */ sci_out(port, SCxSR, SCxSR_RDxF_CLEAR(port)); } |