linux-kernel - [PATCH v2] rcutorture: Reuse value read using READ

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Date: Wed,  6 Mar 2024 10:05:20 +0800
From: linke li <lilinke99@...com>
To: 
Cc: lilinke99@...com,
	Joel Fernandes <joel@...lfernandes.org>,
	Davidlohr Bueso <dave@...olabs.net>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Josh Triplett <josh@...htriplett.org>,
	Frederic Weisbecker <frederic@...nel.org>,
	Neeraj Upadhyay <quic_neeraju@...cinc.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>,
	linux-kernel@...r.kernel.org,
	rcu@...r.kernel.org
Subject: [PATCH v2] rcutorture: Reuse value read using READ_ONCE instead of re-reading it

rp->rtort_pipe_count is modified concurrently by rcu_torture_writer(). To
prevent a data race, reuse i which is read using READ_ONCE before instead
of re-reading it.

Signed-off-by: linke li <lilinke99@...com>
Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>
---
v1 -> v2: change the patch to focus on data race in rcu_torture_pipe_update_one ; update change log

 kernel/rcu/rcutorture.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 7567ca8e743c..53415121be39 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -466,7 +466,7 @@ rcu_torture_pipe_update_one(struct rcu_torture *rp)
 		i = RCU_TORTURE_PIPE_LEN;
 	atomic_inc(&rcu_torture_wcount[i]);
 	WRITE_ONCE(rp->rtort_pipe_count, i + 1);
-	if (rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
+	if (i + 1 >= RCU_TORTURE_PIPE_LEN) {
 		rp->rtort_mbtest = 0;
 		return true;
 	}
-- 
2.39.3 (Apple Git-145)