From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f195.google.com ([209.85.216.195]:43079 "EHLO mail-qt0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752109AbeBSIUM (ORCPT ); Mon, 19 Feb 2018 03:20:12 -0500 MIME-Version: 1.0 In-Reply-To: <20180216184406.GA9286@kroah.com> References: <1518696147-23790-1-git-send-email-ulrich.hecht+renesas@gmail.com> <20180216184406.GA9286@kroah.com> From: Geert Uytterhoeven Date: Mon, 19 Feb 2018 09:20:10 +0100 Message-ID: Subject: Re: [PATCH] serial: sh-sci: prevent lockup on full TTY buffers To: Greg KH Cc: Ulrich Hecht , Linux-Renesas , linux-serial@vger.kernel.org, Wolfram Sang , Yoshihiro Shimoda Content-Type: text/plain; charset="UTF-8" Sender: linux-renesas-soc-owner@vger.kernel.org List-ID: Hi Greg, On Fri, Feb 16, 2018 at 7:44 PM, Greg KH wrote: > 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? This code path dates back to full-history-linux commit 2898a0e08c6ffb63 ("[PATCH] SH Merge") in 2.6.2, back in 2004. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds