From 2ccaff10f71307ad4f75ce673b815d3fe6254e3d Mon Sep 17 00:00:00 2001
From: "Paul E. McKenney" <paulmck@linux.ibm.com>
Date: Wed, 12 Dec 2018 12:32:06 -0800
Subject: rcu: Add sysrq rcu_node-dump capability

Life is hard if RCU manages to get stuck without triggering RCU CPU
stall warnings or triggering the rcu_check_gp_start_stall() checks
for failing to start a grace period.  This commit therefore adds a
boot-time-selectable sysrq key (commandeering "y") that allows manually
dumping Tree RCU state.  The new rcutree.sysrq_rcu kernel boot parameter
must be set for this sysrq to be available.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 5 +++++
 1 file changed, 5 insertions(+)

(limited to 'Documentation')

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index b799bcf67d7b..b0dbb2fa401f 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3721,6 +3721,11 @@
 			This wake_up() will be accompanied by a
 			WARN_ONCE() splat and an ftrace_dump().
 
+	rcutree.sysrq_rcu= [KNL]
+			Commandeer a sysrq key to dump out Tree RCU's
+			rcu_node tree with an eye towards determining
+			why a new grace period has not yet started.
+
 	rcuperf.gp_async= [KNL]
 			Measure performance of asynchronous
 			grace-period primitives such as call_rcu().
-- 
cgit v1.2.3