linux-kernel - Re: [PATCH 1/8] rcu/exp: Remove full barrier upon main thread wakeup

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Message-ID: <ZbkaBO99-6ZuNCcR@localhost.localdomain>
Date: Tue, 30 Jan 2024 16:47:16 +0100
From: Frederic Weisbecker <frederic@...nel.org>
To: Boqun Feng <boqun.feng@...il.com>
Cc: linux-kernel@...r.kernel.org, rcu@...r.kernel.org,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Neeraj Upadhyay <neeraj.iitr10@...il.com>,
	Joel Fernandes <joel@...lfernandes.org>,
	Josh Triplett <josh@...htriplett.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>
Subject: Re: [PATCH 1/8] rcu/exp: Remove full barrier upon main thread wakeup

Le Mon, Jan 29, 2024 at 03:23:39PM -0800, Boqun Feng a écrit :
> From: Frederic Weisbecker <frederic@...nel.org>
> 
> When an expedited grace period is ending, care must be taken so that all
> the quiescent states propagated up to the root are correctly ordered
> against the wake up of the main expedited grace period workqueue.
> 
> This ordering is already carried through the root rnp locking augmented
> by an smp_mb__after_unlock_lock() barrier.
> 
> Therefore the explicit smp_mb() placed before the wake up is not needed
> and can be removed.
> 
> Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
> Signed-off-by: Paul E. McKenney <paulmck@...nel.org>

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Thanks!