linux-kernel - [PATCH 3/5] rcutorture: Check for no up/down readers at task level

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Message-Id: <20250508234502.1996788-3-paulmck@kernel.org>
Date: Thu,  8 May 2025 16:45:00 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: rcu@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	kernel-team@...a.com,
	rostedt@...dmis.org,
	"Paul E. McKenney" <paulmck@...nel.org>
Subject: [PATCH 3/5] rcutorture: Check for no up/down readers at task level

The design of testing of up/down readers such as srcu_down_read()
and srcu_up_read() assumes that these are tested only by the
rcu_torture_updown() kthread, and never by the rcu_torture_reader()
kthread.  Because we all know which road is paved with good intentions,
this commit adds WARN_ON_ONCE() to verify that things are going to plan.

Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/rcu/rcutorture.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 21ff365fca5d9..d94b24f19cf59 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -2231,6 +2231,7 @@ rcutorture_loop_extend(int *readstate, bool insoftirq, struct torture_random_sta
 	i = ((i | (i >> 3)) & RCUTORTURE_RDR_MAX_LOOPS) + 1;
 	for (j = 0; j < i; j++) {
 		mask = rcutorture_extend_mask(*readstate, trsp);
+		WARN_ON_ONCE(mask & RCUTORTURE_RDR_UPDOWN);
 		rcutorture_one_extend(readstate, mask, insoftirq, trsp, &rtrsp[j]);
 	}
 	return &rtrsp[j];
@@ -2367,6 +2368,7 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp, long myid)
 	WARN_ON_ONCE(!rcu_is_watching());
 	init_rcu_torture_one_read_state(&rtors, trsp);
 	newstate = rcutorture_extend_mask(rtors.readstate, trsp);
+	WARN_ON_ONCE(newstate & RCUTORTURE_RDR_UPDOWN);
 	rcutorture_one_extend(&rtors.readstate, newstate, myid < 0, trsp, rtors.rtrsp++);
 	if (!rcu_torture_one_read_start(&rtors, trsp, myid)) {
 		rcutorture_one_extend(&rtors.readstate, 0, myid < 0, trsp, rtors.rtrsp);
-- 
2.40.1