linux-kernel - Re: [PATCH] lockdep: Avoid triggering hardlockup from debug_show_all

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Message-ID: <20180123160054.325ff326@gandalf.local.home>
Date:   Tue, 23 Jan 2018 16:00:54 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Tejun Heo <tj@...nel.org>
Cc:     Rik van Riel <riel@...com>, Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        kernel-team@...com,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Petr Mladek <pmladek@...e.com>
Subject: Re: [PATCH] lockdep: Avoid triggering hardlockup from
 debug_show_all_locks()

On Tue, 23 Jan 2018 12:57:06 -0800
Tejun Heo <tj@...nel.org> wrote:

> Yeah, it's ridiculous how often printk ends up escalating otherwise
> recoverable situations into system crashes.  I don't know what the
> right answer is.  For spurious NMI hardlockups, maybe auditing debug
> paths and adding touch_nmi_watchdog() would be enough but that also is
> a pretty leaky approach.

What about if every printk were to touch NMI watchdog?

NMI watchdog is really there for when the system locks up. If the
system is locked up doing printk, at least we see what is happening,
and not a total freeze.

-- Steve