[PATCH 8/9] rcutorture: Complain if an ->up_read() is delayed more than 10 seconds

["Paul E. McKenney" <paulmck@kernel.org>]

The down/up SRCU reader testing uses an hrtimer handler to exit the SRCU
read-side critical section.  This might be delayed, and if delayed for
too long, it can prevent the rcutorture run from completing.  This commit
therefore complains if the hrtimer handler is delayed for more than
ten seconds.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/rcutorture.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 3042a7950fe23..fcdd6271f435c 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -2438,6 +2438,7 @@ rcu_torture_reader(void *arg)
 struct rcu_torture_one_read_state_updown {
 	struct hrtimer rtorsu_hrt;
 	bool rtorsu_inuse;
+	unsigned long rtorsu_j;
 	struct torture_random_state rtorsu_trs;
 	struct rcu_torture_one_read_state rtorsu_rtors;
 };
@@ -2522,6 +2523,7 @@ static void rcu_torture_updown_one(struct rcu_torture_one_read_state_updown *rto
 		schedule_timeout_idle(HZ);
 		return;
 	}
+	rtorsup->rtorsu_j = jiffies;
 	smp_store_release(&rtorsup->rtorsu_inuse, true);
 	t = torture_random(&rtorsup->rtorsu_trs) & 0xfffff; // One per million.
 	if (t < 10 * 1000)
@@ -2544,8 +2546,10 @@ rcu_torture_updown(void *arg)
 		for (rtorsup = updownreaders; rtorsup < &updownreaders[n_up_down]; rtorsup++) {
 			if (torture_must_stop())
 				break;
-			if (smp_load_acquire(&rtorsup->rtorsu_inuse))
+			if (smp_load_acquire(&rtorsup->rtorsu_inuse)) {
+				WARN_ON_ONCE(time_after(jiffies, rtorsup->rtorsu_j + 10 * HZ));
 				continue;
+			}
 			rcu_torture_updown_one(rtorsup);
 		}
 		torture_hrtimeout_ms(1, 1000, &rcu_torture_updown_rand);
-- 
2.40.1