linux-kernel - Re: [PATCH 2/3] clear_warn_once: bind a timer to written reset value

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Message-ID: <20201130112024.34bcbbd1@gandalf.local.home>
Date:   Mon, 30 Nov 2020 11:20:24 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Paul Gortmaker <paul.gortmaker@...driver.com>
Cc:     linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        John Ogness <john.ogness@...utronix.de>
Subject: Re: [PATCH 2/3] clear_warn_once: bind a timer to written reset
 value

On Thu, 26 Nov 2020 01:30:28 -0500
Paul Gortmaker <paul.gortmaker@...driver.com> wrote:

> +++ b/Documentation/admin-guide/clearing-warn-once.rst
> @@ -7,3 +7,12 @@ echo 1 > /sys/kernel/debug/clear_warn_once
>  
>  clears the state and allows the warnings to print once again.
>  This can be useful after test suite runs to reproduce problems.
> +
> +Values greater than one set a timer for a periodic state reset; e.g.
> +
> +echo 3600 > /sys/kernel/debug/clear_warn_once

I wonder if the value should be in minutes and not seconds, otherwise, a
wrong value could possibly DoS the machine, if you were to write 2 into it.
If there were a lot of warnings in high frequency events.

Or is dumping out a bunch of warnings every 2 seconds not be a problem?

Anyway, would there ever be a need to have it cleared in less than 1 minute
intervals?

-- Steve


> +
> +will establish an hourly state reset, effectively turning WARN_ONCE
> +into a long period rate-limited warning.