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

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Date:   Thu, 28 Apr 2022 12:39:54 -0600
From:   Jonathan Corbet <corbet@....net>
To:     Joel Savitz <jsavitz@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Cc:     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>,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: Re: [PATCH] Documentation/sysctl: document max_rcu_stall_to_panic

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).

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>
---
 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
 =========================