From: "Paul E. McKenney" <paulmck@kernel.org>
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
rostedt@goodmis.org,
"Joel Fernandes (Google)" <joel@joelfernandes.org>,
Frederic Weisbecker <frederic@kernel.org>,
"Paul E . McKenney" <paulmck@kernel.org>
Subject: [PATCH rcu 4/8] rcu: Use READ_ONCE() for lockless read of rnp->qsmask
Date: Wed, 19 Oct 2022 15:46:55 -0700 [thread overview]
Message-ID: <20221019224659.2499511-4-paulmck@kernel.org> (raw)
In-Reply-To: <20221019224652.GA2499358@paulmck-ThinkPad-P17-Gen-1>
From: "Joel Fernandes (Google)" <joel@joelfernandes.org>
The rnp->qsmask is locklessly accessed from rcutree_dying_cpu(). This
may help avoid load tearing due to concurrent access, KCSAN
issues, and preserve sanity of people reading the mask in tracing.
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/tree.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 0ca21ac0f0648..5ec97e3f7468f 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2106,7 +2106,7 @@ int rcutree_dying_cpu(unsigned int cpu)
if (!IS_ENABLED(CONFIG_HOTPLUG_CPU))
return 0;
- blkd = !!(rnp->qsmask & rdp->grpmask);
+ blkd = !!(READ_ONCE(rnp->qsmask) & rdp->grpmask);
trace_rcu_grace_period(rcu_state.name, READ_ONCE(rnp->gp_seq),
blkd ? TPS("cpuofl-bgp") : TPS("cpuofl"));
return 0;
--
2.31.1.189.g2e36527f23
next prev parent reply other threads:[~2022-10-19 22:47 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-19 22:46 [PATCH rcu 0/8] Miscellaneous fixes for v6.2 Paul E. McKenney
2022-10-19 22:46 ` [PATCH rcu 1/8] rcu: Remove duplicate RCU exp QS report from rcu_report_dead() Paul E. McKenney
2022-10-19 22:46 ` [PATCH rcu 2/8] rcu: Synchronize ->qsmaskinitnext in rcu_boost_kthread_setaffinity() Paul E. McKenney
2022-10-19 22:46 ` [PATCH rcu 3/8] rcu: Remove unused 'cpu' in rcu_virt_note_context_switch() Paul E. McKenney
2022-10-19 22:46 ` Paul E. McKenney [this message]
2022-10-19 22:46 ` [PATCH rcu 5/8] slab: Explain why SLAB_DESTROY_BY_RCU reference before locking Paul E. McKenney
2022-10-20 7:10 ` Vlastimil Babka
2022-10-20 16:31 ` Paul E. McKenney
2022-10-21 7:44 ` Christoph Lameter
2022-10-21 13:43 ` Paul E. McKenney
2022-10-21 13:50 ` Vlastimil Babka
2022-10-21 15:42 ` Paul E. McKenney
2022-10-21 15:50 ` Vlastimil Babka
2022-10-21 16:10 ` Paul E. McKenney
2022-10-19 22:46 ` [PATCH rcu 6/8] rcu: Remove rcu_is_idle_cpu() Paul E. McKenney
2022-10-19 22:46 ` [PATCH rcu 7/8] rcu-tasks: Make grace-period-age message human-readable Paul E. McKenney
2022-10-19 22:46 ` [PATCH rcu 8/8] rcu: Fix __this_cpu_read() lockdep warning in rcu_force_quiescent_state() Paul E. McKenney
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