linux-kernel - [PATCH AUTOSEL 5.15 3/7] rcutorture: Fix rcu_torture_one_read() pipe

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Date: Sun, 26 May 2024 05:43:23 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: "Paul E. McKenney" <paulmck@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Uladzislau Rezki <urezki@...il.com>,
	Sasha Levin <sashal@...nel.org>,
	dave@...olabs.net,
	josh@...htriplett.org,
	frederic@...nel.org,
	neeraj.upadhyay@...nel.org,
	joel@...lfernandes.org,
	boqun.feng@...il.com,
	rcu@...r.kernel.org
Subject: [PATCH AUTOSEL 5.15 3/7] rcutorture: Fix rcu_torture_one_read() pipe_count overflow comment

From: "Paul E. McKenney" <paulmck@...nel.org>

[ Upstream commit 8b9b443fa860276822b25057cb3ff3b28734dec0 ]

The "pipe_count > RCU_TORTURE_PIPE_LEN" check has a comment saying "Should
not happen, but...".  This is only true when testing an RCU whose grace
periods are always long enough.  This commit therefore fixes this comment.

Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>
Closes: https://lore.kernel.org/lkml/CAHk-=wi7rJ-eGq+xaxVfzFEgbL9tdf6Kc8Z89rCpfcQOKm74Tw@mail.gmail.com/
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 d820ef615475b..82c6046db8a42 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1604,7 +1604,8 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp, long myid)
 	preempt_disable();
 	pipe_count = READ_ONCE(p->rtort_pipe_count);
 	if (pipe_count > RCU_TORTURE_PIPE_LEN) {
-		/* Should not happen, but... */
+		// Should not happen in a correct RCU implementation,
+		// happens quite often for torture_type=busted.
 		pipe_count = RCU_TORTURE_PIPE_LEN;
 	}
 	completed = cur_ops->get_gp_seq();
-- 
2.43.0