linux-kernel - Re: [PATCH] Documentation/sysctl: document max_rcu_stall_to

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Message-ID: <20220428184939.GL1790663@paulmck-ThinkPad-P17-Gen-1>
Date:   Thu, 28 Apr 2022 11:49:39 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Jonathan Corbet <corbet@....net>
Cc:     Joel Savitz <jsavitz@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Huang Ying <ying.huang@...el.com>,
        Eric Biggers <ebiggers@...gle.com>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Rob Herring <robh@...nel.org>, Wang Qing <wangqing@...o.com>,
        linux-doc@...r.kernel.org, chao <chao@...o.com>
Subject: Re: [PATCH] Documentation/sysctl: document max_rcu_stall_to_panic

On Thu, Apr 28, 2022 at 12:39:54PM -0600, Jonathan Corbet wrote:
> Joel Savitz <jsavitz@...hat.com> writes:
> 
> > Friendly ping.
> 
> This was waiting for an ack from an RCU person.  Looking now, though, I
> see that you didn't copy any RCU people.  Adding Paul and the author of
> the patch you reference (and appending patch below).

Thank you for calling this to my attention.  ;-)

> Thanks,
> 
> jon
> 
> Joel Savitz <jsavitz@...hat.com> (March 24) (kernel lwn)
> Subject: [PATCH] Documentation/sysctl: document max_rcu_stall_to_panic
> To: linux-kernel@...r.kernel.org
> Cc: Joel Savitz <jsavitz@...hat.com>, Jonathan Corbet <corbet@....net>, Andrew Morton <akpm@...ux-foundation.org>, Huang Ying <ying.huang@...el.com>, Eric Biggers <ebiggers@...gle.com>, Dominik Brodowski <linux@...inikbrodowski.net>, Mauro Carvalho Chehab <mchehab+huawei@...nel.org>, Rasmus Villemoes <linux@...musvillemoes.dk>, "Jason A. Donenfeld" <Jason@...c4.com>, Daniel Borkmann <daniel@...earbox.net>, Rob Herring <robh@...nel.org>, Wang Qing <wangqing@...o.com>, linux-doc@...r.kernel.org
> Date: Thu, 24 Mar 2022 18:11:56 -0400
> 
> commit dfe564045c65 ("rcu: Panic after fixed number of stalls")
> introduced a new systctl but no accompanying documentation.
> 
> Add a simple entry to the documentation.
> 
> Signed-off-by: Joel Savitz <jsavitz@...hat.com>

Acked-by: Paul E. McKenney <paulmck@...nel.org>

> ---
>  Documentation/admin-guide/sysctl/kernel.rst | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
> index 803c60bf21d3..4e48139b9a34 100644
> --- a/Documentation/admin-guide/sysctl/kernel.rst
> +++ b/Documentation/admin-guide/sysctl/kernel.rst
> @@ -781,6 +781,13 @@ is useful to define the root cause of RCU stalls using a vmcore.
>  1 panic() after printing RCU stall messages.
>  = ============================================================
> 
> +max_rcu_stall_to_panic
> +======================
> +
> +When ``panic_on_rcu_stall`` is set to 1, this value determines the
> +number of times that RCU can stall before panic() is called.
> +
> +When ``panic_on_rcu_stall`` is set to 0, this value is has no effect.
> 
>  perf_cpu_time_max_percent
>  =========================