[PATCH] Documentation/sysctl: document max_rcu_stall_to_panic

[PATCH] Documentation/sysctl: document max_rcu_stall_to_panic

[Joel Savitz]

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@redhat.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
 =========================
-- 
2.27.0

Re: [PATCH] Documentation/sysctl: document max_rcu_stall_to_panic

[Joel Savitz]

Friendly ping.

Joel

Re: [PATCH] Documentation/sysctl: document max_rcu_stall_to_panic

[Jonathan Corbet]

Joel Savitz <jsavitz@redhat.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@redhat.com> (March 24) (kernel lwn)
Subject: [PATCH] Documentation/sysctl: document max_rcu_stall_to_panic
To: linux-kernel@vger.kernel.org
Cc: Joel Savitz <jsavitz@redhat.com>, Jonathan Corbet <corbet@lwn.net>, Andrew Morton <akpm@linux-foundation.org>, Huang Ying <ying.huang@intel.com>, Eric Biggers <ebiggers@google.com>, Dominik Brodowski <linux@dominikbrodowski.net>, Mauro Carvalho Chehab <mchehab+huawei@kernel.org>, Rasmus Villemoes <linux@rasmusvillemoes.dk>, "Jason A. Donenfeld" <Jason@zx2c4.com>, Daniel Borkmann <daniel@iogearbox.net>, Rob Herring <robh@kernel.org>, Wang Qing <wangqing@vivo.com>, linux-doc@vger.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@redhat.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
 =========================

Re: [PATCH] Documentation/sysctl: document max_rcu_stall_to_panic

[Paul E. McKenney]

On Thu, Apr 28, 2022 at 12:39:54PM -0600, Jonathan Corbet wrote:
> Joel Savitz <jsavitz@redhat.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@redhat.com> (March 24) (kernel lwn)
> Subject: [PATCH] Documentation/sysctl: document max_rcu_stall_to_panic
> To: linux-kernel@vger.kernel.org
> Cc: Joel Savitz <jsavitz@redhat.com>, Jonathan Corbet <corbet@lwn.net>, Andrew Morton <akpm@linux-foundation.org>, Huang Ying <ying.huang@intel.com>, Eric Biggers <ebiggers@google.com>, Dominik Brodowski <linux@dominikbrodowski.net>, Mauro Carvalho Chehab <mchehab+huawei@kernel.org>, Rasmus Villemoes <linux@rasmusvillemoes.dk>, "Jason A. Donenfeld" <Jason@zx2c4.com>, Daniel Borkmann <daniel@iogearbox.net>, Rob Herring <robh@kernel.org>, Wang Qing <wangqing@vivo.com>, linux-doc@vger.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@redhat.com>

Acked-by: Paul E. McKenney <paulmck@kernel.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
>  =========================

Re: [PATCH] Documentation/sysctl: document max_rcu_stall_to_panic

[Jonathan Corbet]

"Paul E. McKenney" <paulmck@kernel.org> writes:

>> 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@redhat.com>
>
> Acked-by: Paul E. McKenney <paulmck@kernel.org>

OK, applied, thanks.

jon