3.2.102-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Ulrich Hecht <[email protected]> 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 <[email protected]> Signed-off-by: Ulrich Hecht <[email protected]> Reviewed-by: Geert Uytterhoeven <[email protected]> Tested-by: Nguyen Viet Dung <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> [bwh: Backported to 3.2: - Use sci_in() - Adjust context] Signed-off-by: Ben Hutchings <[email protected]> --- 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 @@ -668,6 +668,8 @@ static void sci_receive_chars(struct uar /* 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)); }
