From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg KH Subject: Re: [PATCH] serial: sh-sci: prevent lockup on full TTY buffers Date: Fri, 16 Feb 2018 19:44:06 +0100 Message-ID: <20180216184406.GA9286@kroah.com> References: <1518696147-23790-1-git-send-email-ulrich.hecht+renesas@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1518696147-23790-1-git-send-email-ulrich.hecht+renesas@gmail.com> Sender: linux-renesas-soc-owner@vger.kernel.org To: Ulrich Hecht Cc: linux-renesas-soc@vger.kernel.org, linux-serial@vger.kernel.org, wsa@the-dreams.de, geert@linux-m68k.org, yoshihiro.shimoda.uh@renesas.com List-Id: linux-serial@vger.kernel.org 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 > Signed-off-by: Ulrich Hecht Should this go to older kernel versions as well? If so, how far back? thanks, greg k-h