From: Rusty Russell <rusty@rustcorp.com.au>
To: Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH 07/19] stop_machine: reimplement without using workqueue
Date: Tue, 6 Oct 2009 20:06:58 +1030
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On Thu, 1 Oct 2009 05:39:06 pm Tejun Heo wrote:
> stop_machine() is the only user of RT workqueue.  Reimplement it using
> kthreads directly and rip RT support from workqueue.  This is in
> preparation of concurrency managed workqueue.

Seems reasonable, but:

>  void stop_machine_destroy(void)
>  {
> +	get_online_cpus();
>  	mutex_lock(&setup_lock);

Did you test hotplug cpu after this change?  Maybe this works fine, but it's
always the one we break when we play with this code :(

Thanks!
Rusty.
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