linux-kernel - [PATCH tip/core/rcu 11/21] rcutorture: Halt forward-progress checks at end of run

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Message-Id: <20190530151712.1612-11-paulmck@linux.ibm.com>
Date:   Thu, 30 May 2019 08:17:02 -0700
From:   "Paul E. McKenney" <paulmck@...ux.ibm.com>
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, mingo@...nel.org,
        jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        fweisbec@...il.com, oleg@...hat.com, joel@...lfernandes.org,
        "Paul E. McKenney" <paulmck@...ux.ibm.com>
Subject: [PATCH tip/core/rcu 11/21] rcutorture: Halt forward-progress checks at end of run

Once removed, an rcu_torture element can be deferred-freed by a chain
of call_rcu() invocations, with each callback invoking another round of
call_rcu() until either a fixed number of call_rcu() invocations have
been chained or until the test ends.  This means that if the test ends,
some of the rcu_torture elements will be "stranded" partway through the
deferred-free process, which results in false-positive warnings from
rcu_torture_writer() due to lack of forward progress should the test
end just at the end of a stutter interval.

This commit therefore suppresses rcu_torture_writer()'s forward-progress
checks when the test ends in order to avoid these false-positive reports..

Reported-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Signed-off-by: Paul E. McKenney <paulmck@...ux.ibm.com>
---
 kernel/rcu/rcutorture.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index ef6f6dedf4c4..a3f5488a319a 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1014,7 +1014,8 @@ rcu_torture_writer(void *arg)
 		rcu_torture_writer_state = RTWS_STUTTER;
 		if (stutter_wait("rcu_torture_writer") &&
 		    !READ_ONCE(rcu_fwd_cb_nodelay) &&
-		    !cur_ops->slow_gps)
+		    !cur_ops->slow_gps &&
+		    !torture_must_stop())
 			for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++)
 				if (list_empty(&rcu_tortures[i].rtort_free) &&
 				    rcu_access_pointer(rcu_torture_current) !=
-- 
2.17.1