linux-kernel - [PATCH] rcutorture: Avoid soft lockup during cpu stall

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Message-Id: <20211109174602.407644-1-wander@redhat.com>
Date:   Tue,  9 Nov 2021 14:46:02 -0300
From:   wander@...hat.com
To:     Davidlohr Bueso <dave@...olabs.net>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        linux-kernel@...r.kernel.org (open list:TORTURE-TEST MODULES),
        rcu@...r.kernel.org (open list:READ-COPY UPDATE (RCU))
Cc:     Wander Lairson Costa <wander@...hat.com>
Subject: [PATCH] rcutorture: Avoid soft lockup during cpu stall

From: Wander Lairson Costa <wander@...hat.com>

If we use the module stall_cpu option, we may get a soft lockup warning
if we also don't pass the stall_cpu_block option.

We introduce the stall_no_softlockup option to avoid a soft lockup on
cpu stall even if we don't use the stall_cpu_block option.

Signed-off-by: Wander Lairson Costa <wander@...hat.com>
---
 kernel/rcu/rcutorture.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 40ef5417d954..0a2a9a6533d1 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -10,6 +10,7 @@
  * See also:  Documentation/RCU/torture.rst
  */
 
+#include "linux/nmi.h"
 #define pr_fmt(fmt) fmt
 
 #include <linux/types.h>
@@ -109,6 +110,8 @@ torture_param(int, shutdown_secs, 0, "Shutdown time (s), <= zero to disable.");
 torture_param(int, stall_cpu, 0, "Stall duration (s), zero to disable.");
 torture_param(int, stall_cpu_holdoff, 10,
 	     "Time to wait before starting stall (s).");
+torture_param(bool, stall_no_softlockup, false,
+	     "Avoid softlockup warning during cpu stall.");
 torture_param(int, stall_cpu_irqsoff, 0, "Disable interrupts while stalling.");
 torture_param(int, stall_cpu_block, 0, "Sleep while stalling.");
 torture_param(int, stall_gp_kthread, 0,
@@ -2024,6 +2027,8 @@ static int rcu_torture_stall(void *args)
 				    stop_at))
 			if (stall_cpu_block)
 				schedule_timeout_uninterruptible(HZ);
+			else if (stall_no_softlockup)
+				touch_softlockup_watchdog();
 		if (stall_cpu_irqsoff)
 			local_irq_enable();
 		else if (!stall_cpu_block)
-- 
2.27.0