linux-kernel - Re: [RFC 06/10] rcu/hotplug: Make rcutree_dead

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Date:   Wed, 24 Aug 2022 09:44:59 -0400
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Pingfan Liu <kernelfans@...il.com>
Cc:     Joel Fernandes <joel@...lfernandes.org>,
        LKML <linux-kernel@...r.kernel.org>, rcu <rcu@...r.kernel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Price <steven.price@....com>,
        Mark Rutland <mark.rutland@....com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Subject: Re: [RFC 06/10] rcu/hotplug: Make rcutree_dead_cpu() parallel

On 8/22/22, Pingfan Liu <kernelfans@...il.com> wrote:
> On Mon, Aug 22, 2022 at 02:08:38PM -0400, Joel Fernandes wrote:
>> On Sun, Aug 21, 2022 at 10:16 PM Pingfan Liu <kernelfans@...il.com>
>> wrote:
>> >
>> > In order to support parallel, rcu_state.n_online_cpus should be
>> > atomic_dec()
>>
>> What does Parallel mean? Is that some kexec terminology?
>>
>
> 'Parallel' means concurrent. It is not a kexec terminology, instead,
> should be SMP.

Only sort of. See section A.6 of Paul 's book:
http://kernel.org/pub/linux/kernel/people/paulmck/perfbook/perfbook.html

Jason