linux-kernel - Re: [PATCH] rcutorture: Traverse possible cpu to set maxcpu in rcu_nocb

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Date:   Tue, 29 Aug 2023 06:12:35 -0400
From:   Joel Fernandes <joel@...lfernandes.org>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     "Paul E. McKenney" <paulmck@...nel.org>,
        Z qiang <qiang.zhang1211@...il.com>,
        linux-kernel@...r.kernel.org, rcu@...r.kernel.org
Subject: Re: [PATCH] rcutorture: Traverse possible cpu to set maxcpu in rcu_nocb_toggle()



> On Aug 29, 2023, at 5:24 AM, Frederic Weisbecker <frederic@...nel.org> wrote:
> 
> On Mon, Aug 28, 2023 at 05:51:09PM -0400, Joel Fernandes wrote:
>> I think the issue is the loop later in the function does
>> not try to toggle cpus that came online too late.
>> 
>> So it does not test offloading on all CPUs just because max got updated too
>> late.
> 
> Right, and therefore for_each_possible_cpu() or for_each_present_cpu()
> should be fine to iterate since it's ok to try to toggle an offline CPU.

Ah I see what you mean, sounds good.

> 
>> 
>> One fix could be to periodically check in the loop if a new cpu at maxcpu + 1
>> ever got onlined. If it did, update the maxcpu.
> 
> Is it worth the complication though?

Probably not and so your suggestion sounds fine.

Thanks!

 - Joel


> 
> Thanks.
> 
>> 
>> Thanks.
>> 
>> 
>>> 
>>> Thanks.