[PATCH v2] Documentation: Better document the softlockup_panic sysctl

["Guilherme G. Piccoli" <gpiccoli@canonical.com>]

Commit 9c44bc03fff4 ("softlockup: allow panic on lockup") added the
softlockup_panic sysctl, but didn't add information about it to the file
Documentation/admin-guide/sysctl/kernel.rst (which in that time certainly
wasn't rst and had other name!).

This patch just adds the respective documentation and references it from
the corresponding entry in Documentation/admin-guide/kernel-parameters.txt.

This patch was strongly based on Scott Wood's commit d22881dc13b6
("Documentation: Better document the hardlockup_panic sysctl").

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@canonical.com>
---
 Documentation/admin-guide/kernel-parameters.txt |  8 ++++----
 Documentation/admin-guide/sysctl/kernel.rst     | 14 ++++++++++++++
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 04615690e69e..b24fb0d11955 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4578,10 +4578,10 @@
 			Format: <integer>
 
 			A nonzero value instructs the soft-lockup detector
-			to panic the machine when a soft-lockup occurs. This
-			is also controlled by CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC
-			which is the respective build-time switch to that
-			functionality.
+			to panic the machine when a soft-lockup occurs. It is
+			also controlled by the kernel.softlockup_panic sysctl
+			and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
+			respective build-time switch to that functionality.
 
 	softlockup_all_cpu_backtrace=
 			[KNL] Should the soft-lockup detector generate
diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index 1c48ab4bfe30..335696d3360d 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -1036,6 +1036,20 @@ NMI.
 = ============================================
 
 
+softlockup_panic
+=================
+
+This parameter can be used to control whether the kernel panics
+when a soft lockup is detected.
+
+= ============================================
+0 Don't panic on soft lockup.
+1 Panic on soft lockup.
+= ============================================
+
+This can also be set using the softlockup_panic kernel parameter.
+
+
 soft_watchdog
 =============
 
-- 
2.25.1