linux-kernel - Re: [PATCH 1/1] rcu/sync: simplify the state machine

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Message-ID: <20190429160603.GC17715@redhat.com>
Date:   Mon, 29 Apr 2019 18:06:04 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     "Paul E. McKenney" <paulmck@...ux.ibm.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Josh Triplett <josh@...htriplett.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] rcu/sync: simplify the state machine

On 04/28, Paul E. McKenney wrote:
>
> And it still looks good after review, so I have pushed it.

Thanks!

> I did add
> READ_ONCE() and WRITE_ONCE() to unprotected uses of ->gp_state, but
> please let me know if I messed anything up.

Well, at least WRITE_ONCE()'s look certainly unneeded to me, gp_state
is protected by rss_lock.

WARN_ON_ONCE(gp_state) can read gp_state lockless, but even in this case
I do not understand what READ_ONCE() tries to prevent...

Nevermind, this won't hurt and as I already said I don't understand the
_ONCE() magic anyway ;)

Thanks,

Oleg.