linux-kernel - Re: [PATCH 5/6] rcu: Remove full memory barrier on RCU stall printout

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Message-ID: <xhsmh7cftheff.mognet@vschneid-thinkpadt14sgen2i.remote.csb>
Date: Thu, 16 May 2024 19:09:08 +0200
From: Valentin Schneider <vschneid@...hat.com>
To: Frederic Weisbecker <frederic@...nel.org>, LKML
 <linux-kernel@...r.kernel.org>
Cc: Frederic Weisbecker <frederic@...nel.org>, "Paul E . McKenney"
 <paulmck@...nel.org>, Boqun Feng <boqun.feng@...il.com>, Joel Fernandes
 <joel@...lfernandes.org>, Neeraj Upadhyay <neeraj.upadhyay@....com>,
 Uladzislau Rezki <urezki@...il.com>, Zqiang <qiang.zhang1211@...il.com>,
 rcu <rcu@...r.kernel.org>
Subject: Re: [PATCH 5/6] rcu: Remove full memory barrier on RCU stall printout

On 15/05/24 14:53, Frederic Weisbecker wrote:
> RCU stall printout fetches the EQS state of a CPU with a preceding full
> memory barrier. However there is nothing to order this read against at
> this debugging stage. It is inherently racy when performed remotely.
>
> Do a plain read instead.
>
> This was the last user of rcu_dynticks_snap().
>
> Signed-off-by: Frederic Weisbecker <frederic@...nel.org>

Reviewed-by: Valentin Schneider <vschneid@...hat.com>