rcutorture: Avoid soft lockup during cpu stall

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

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

kernel/rcu/rcutorture.c

@@ -46,6 +46,7 @@
 #include <linux/oom.h>
 #include <linux/tick.h>
 #include <linux/rcupdate_trace.h>
+#include <linux/nmi.h>
 
 #include "rcu.h"
 
@@ -112,6 +113,8 @@ 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,
@@ -2085,6 +2088,8 @@ static int rcu_torture_stall(void *args)
 #else
 				schedule_timeout_uninterruptible(HZ);
 #endif
+			} else if (stall_no_softlockup) {
+				touch_softlockup_watchdog();
 			}
 		if (stall_cpu_irqsoff)
 			local_irq_enable();