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Message-ID: <tencent_B51A9DA220288A95A435E3435A0443BEB007@qq.com>
Date: Mon, 4 Mar 2024 18:54:46 +0800
From: linke li <lilinke99@...com>
To:
Cc: lilinke99@...com,
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>,
Joel Fernandes <joel@...lfernandes.org>,
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] rcutorture: Fix rcu_torture_pipe_update_one()/rcu_torture_writer() data race and concurrency bug
Some changes are done to fix a data race in commit 202489101f2e ("rcutorture: Fix rcu_torture_one_read()/rcu_torture_writer() data race")
{
int i;
- i = rp->rtort_pipe_count;
+ i = READ_ONCE(rp->rtort_pipe_count);
if (i > RCU_TORTURE_PIPE_LEN)
i = RCU_TORTURE_PIPE_LEN;
atomic_inc(&rcu_torture_wcount[i]);
- if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
+ WRITE_ONCE(rp->rtort_pipe_count, i + 1);
+ if (rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
rp->rtort_mbtest = 0;
return true;
}
But ++rp->rtort_pipe_count is meant to add itself by 1, not give i+1 to
rp->rtort_pipe_count, because rp->rtort_pipe_count may write by
rcu_torture_writer() concurrently.
Also, rp->rtort_pipe_count in the next line should be read using
READ_ONCE() because of data race.
Signed-off-by: linke li <lilinke99@...com>
---
kernel/rcu/rcutorture.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 7567ca8e743c..00059ace4fd5 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -465,8 +465,8 @@ rcu_torture_pipe_update_one(struct rcu_torture *rp)
if (i > RCU_TORTURE_PIPE_LEN)
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) {
+ WRITE_ONCE(rp->rtort_pipe_count, rp->rtort_pipe_count + 1);
+ if (READ_ONCE(rp->rtort_pipe_count) >= RCU_TORTURE_PIPE_LEN) {
rp->rtort_mbtest = 0;
return true;
}
--
2.39.3 (Apple Git-145)
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