Re: [PATCH] serial: sh-sci: prevent lockup on full TTY buffers

[Greg KH <greg@kroah.com>]

On Thu, Feb 15, 2018 at 01:02:27PM +0100, Ulrich Hecht wrote:
> 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>

Should this go to older kernel versions as well?
If so, how far back?

thanks,

greg k-h