[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20240728004901.1704470-2-sashal@kernel.org>
Date: Sat, 27 Jul 2024 20:48:55 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
stable@...r.kernel.org
Cc: "Paul E. McKenney" <paulmck@...nel.org>,
Marco Elver <elver@...gle.com>,
Andrey Konovalov <andreyknvl@...il.com>,
kasan-dev@...glegroups.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,
urezki@...il.com,
rcu@...r.kernel.org
Subject: [PATCH AUTOSEL 5.10 2/6] rcutorture: Fix rcu_torture_fwd_cb_cr() data race
From: "Paul E. McKenney" <paulmck@...nel.org>
[ Upstream commit 6040072f4774a575fa67b912efe7722874be337b ]
On powerpc systems, spinlock acquisition does not order prior stores
against later loads. This means that this statement:
rfcp->rfc_next = NULL;
Can be reordered to follow this statement:
WRITE_ONCE(*rfcpp, rfcp);
Which is then a data race with rcu_torture_fwd_prog_cr(), specifically,
this statement:
rfcpn = READ_ONCE(rfcp->rfc_next)
KCSAN located this data race, which represents a real failure on powerpc.
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Acked-by: Marco Elver <elver@...gle.com>
Cc: Andrey Konovalov <andreyknvl@...il.com>
Cc: <kasan-dev@...glegroups.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
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 9f505688291e5..5c4bdbe76df04 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1867,7 +1867,7 @@ static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp)
spin_lock_irqsave(&rfp->rcu_fwd_lock, flags);
rfcpp = rfp->rcu_fwd_cb_tail;
rfp->rcu_fwd_cb_tail = &rfcp->rfc_next;
- WRITE_ONCE(*rfcpp, rfcp);
+ smp_store_release(rfcpp, rfcp);
WRITE_ONCE(rfp->n_launders_cb, rfp->n_launders_cb + 1);
i = ((jiffies - rfp->rcu_fwd_startat) / (HZ / FWD_CBS_HIST_DIV));
if (i >= ARRAY_SIZE(rfp->n_launders_hist))
--
2.43.0
Powered by blists - more mailing lists