[PATCH] 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").

Signed-off-by: Guilherme G. Piccoli <gpiccoli@canonical.com>
---
 Documentation/admin-guide/kernel-parameters.txt |  6 +++---
 Documentation/admin-guide/sysctl/kernel.rst     | 13 +++++++++++++
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index c07815d230bc..adf77ead02c3 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4515,9 +4515,9 @@
 
 			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.
+			is also controlled by 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 def074807cee..95b2f3256323 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -95,6 +95,7 @@ show up in /proc/sys/kernel:
 - shmmax                      [ sysv ipc ]
 - shmmni
 - softlockup_all_cpu_backtrace
+- softlockup_panic
 - soft_watchdog
 - stack_erasing
 - stop-a                      [ SPARC only ]
@@ -1029,6 +1030,18 @@ NMI.
 1: on detection capture more debug information.
 
 
+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:
 ==============
 
-- 
2.24.1