linux-kernel - Re: [PATCH 2/4] stop_machine: reimplement using cpuhog

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Date:	Mon, 8 Mar 2010 20:06:07 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	linux-kernel@...r.kernel.org, rusty@...tcorp.com.au,
	sivanich@....com, heiko.carstens@...ibm.com,
	torvalds@...ux-foundation.org, mingo@...e.hu, peterz@...radead.org,
	dipankar@...ibm.com, josh@...edesktop.org,
	paulmck@...ux.vnet.ibm.com, akpm@...ux-foundation.org
Subject: Re: [PATCH 2/4] stop_machine: reimplement using cpuhog

On 03/09, Tejun Heo wrote:
>
>  int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus)
>  {
> ...
> +	/* Set the initial state and hog all online cpus. */
> +	set_state(&smdata, STOPMACHINE_PREPARE);
> +	return hog_cpus(cpu_online_mask, stop_cpu, &smdata);
>  }

Could you please confirm this is correct?

I am not sure I understand how the code looks with the patch applied,
but the lockless set_state() above can confuse another stop_machine()
in progress?

Oleg.

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