linux-kernel - [PATCH rcu 07/25] rcutorture: Verify long-running reader prevents full polling from completing

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Message-Id: <20220831181210.2695080-7-paulmck@kernel.org>
Date:   Wed, 31 Aug 2022 11:11:52 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com,
        rostedt@...dmis.org, "Paul E. McKenney" <paulmck@...nel.org>
Subject: [PATCH rcu 07/25] rcutorture: Verify long-running reader prevents full polling from completing

This commit adds full-state polling checks to accompany the old-style
polling checks in the rcu_torture_one_read() function.  If a polling
cycle within an RCU reader completes, a WARN_ONCE() is triggered.

Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/rcu/rcutorture.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 236bd6b57277f..3d85420108477 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1770,6 +1770,7 @@ rcutorture_loop_extend(int *readstate, struct torture_random_state *trsp,
 static bool rcu_torture_one_read(struct torture_random_state *trsp, long myid)
 {
 	unsigned long cookie;
+	struct rcu_gp_oldstate cookie_full;
 	int i;
 	unsigned long started;
 	unsigned long completed;
@@ -1787,6 +1788,8 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp, long myid)
 	rcutorture_one_extend(&readstate, newstate, trsp, rtrsp++);
 	if (cur_ops->get_gp_state && cur_ops->poll_gp_state)
 		cookie = cur_ops->get_gp_state();
+	if (cur_ops->get_gp_state_full && cur_ops->poll_gp_state_full)
+		cur_ops->get_gp_state_full(&cookie_full);
 	started = cur_ops->get_gp_seq();
 	ts = rcu_trace_clock_local();
 	p = rcu_dereference_check(rcu_torture_current,
@@ -1827,6 +1830,13 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp, long myid)
 			  rcu_torture_writer_state_getname(),
 			  rcu_torture_writer_state,
 			  cookie, cur_ops->get_gp_state());
+	if (cur_ops->get_gp_state_full && cur_ops->poll_gp_state_full)
+		WARN_ONCE(cur_ops->poll_gp_state_full(&cookie_full),
+			  "%s: Cookie check 6 failed %s(%d) online %*pbl\n",
+			  __func__,
+			  rcu_torture_writer_state_getname(),
+			  rcu_torture_writer_state,
+			  cpumask_pr_args(cpu_online_mask));
 	rcutorture_one_extend(&readstate, 0, trsp, rtrsp);
 	WARN_ON_ONCE(readstate);
 	// This next splat is expected behavior if leakpointer, especially
-- 
2.31.1.189.g2e36527f23