From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1758116AbdJMNTB (ORCPT <rfc822;w@1wt.eu>);
        Fri, 13 Oct 2017 09:19:01 -0400
Received: from mail.kernel.org ([198.145.29.99]:36590 "EHLO mail.kernel.org"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1753438AbdJMNTA (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Fri, 13 Oct 2017 09:19:00 -0400
DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org ADFC621874
Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org
Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=rostedt@goodmis.org
Date: Fri, 13 Oct 2017 09:18:57 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: Petr Mladek <pmladek@suse.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>
Subject: Re: NMI watchdog dump does not print on hard lockup
Message-ID: <20171013091857.4afe8a7a@gandalf.local.home>
In-Reply-To: <20171013111444.GB2795@pathway.suse.cz>
References: <20171012121658.187c5af6@gandalf.local.home>
        <20171013111444.GB2795@pathway.suse.cz>
X-Mailer: Claws Mail 3.14.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Fri, 13 Oct 2017 13:14:44 +0200
Petr Mladek <pmladek@suse.com> wrote:

> In general, we could either improve detection of situations when
> the entire system is locked. It would be a reason to risk calling
> consoles even in NMI.
> 
> Or we could accept that the "default" printk is not good for all
> situations and allow more special "debugging" modes:
> 
> 	   + Peter's force_early_printk stuff
> 
> 	   + Allow to disable printk_safe and printk_safe_nmi.
> 	     There will be a risk of a deadlock caused by printk.
> 	     But there also will be a chance to see the messages.

Or add the following case: The watchdog triggers, does the print, then
if it triggers again in a certain amount of time, and the print still
hasn't been flushed, the flush happens then.

-- Steve