From: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
To: Frederic Weisbecker <frederic@kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Cc: Zqiang <qiang.zhang1211@gmail.com>,
Boqun Feng <boqun.feng@gmail.com>,
Joel Fernandes <joel@joelfernandes.org>,
Josh Triplett <josh@joshtriplett.org>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
"Paul E . McKenney" <paulmck@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Uladzislau Rezki <urezki@gmail.com>, rcu <rcu@vger.kernel.org>
Subject: Re: [PATCH 2/2] rcu/nocb: Fix missed RCU barrier on deoffloading
Date: Mon, 11 Nov 2024 13:07:16 +0530 [thread overview]
Message-ID: <68c39e33-6281-4978-ba4e-131c6336aa7e@amd.com> (raw)
In-Reply-To: <20241106153213.38896-3-frederic@kernel.org>
> diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
> index 16865475120b..2605dd234a13 100644
> --- a/kernel/rcu/tree_nocb.h
> +++ b/kernel/rcu/tree_nocb.h
> @@ -891,7 +891,18 @@ static void nocb_cb_wait(struct rcu_data *rdp)
> swait_event_interruptible_exclusive(rdp->nocb_cb_wq,
> nocb_cb_wait_cond(rdp));
> if (kthread_should_park()) {
> - kthread_parkme();
> + /*
> + * kthread_park() must be preceded by an rcu_barrier().
> + * But yet another rcu_barrier() might have sneaked in between
> + * the barrier callback execution and the callbacks counter
> + * decrement.
> + */
> + if (rdp->nocb_cb_sleep) {
Is READ_ONCE() not required here?
- Neeraj
> + rcu_nocb_lock_irqsave(rdp, flags);
> + WARN_ON_ONCE(rcu_segcblist_n_cbs(&rdp->cblist));
> + rcu_nocb_unlock_irqrestore(rdp, flags);
> + kthread_parkme();
> + }
> } else if (READ_ONCE(rdp->nocb_cb_sleep)) {
> WARN_ON(signal_pending(current));
> trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WokeEmpty"));
next prev parent reply other threads:[~2024-11-11 7:37 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-11-06 15:32 [PATCH 0/2] RCU NOCB for v6.13 Frederic Weisbecker
2024-11-06 15:32 ` [PATCH 1/2] rcu: Remove unused declaration rcu_segcblist_offload() Frederic Weisbecker
2024-11-06 15:32 ` [PATCH 2/2] rcu/nocb: Fix missed RCU barrier on deoffloading Frederic Weisbecker
2024-11-11 7:37 ` Neeraj Upadhyay [this message]
2024-11-12 21:37 ` Frederic Weisbecker
2024-11-13 3:22 ` Neeraj Upadhyay
2024-11-11 17:33 ` [PATCH 0/2] RCU NOCB for v6.13 Neeraj Upadhyay
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