Re: [PATCH 07/19] acpi: use queue_work_on() instead of binding workqueue worker to cpu0

[Andrew Morton <akpm@linux-foundation.org>]

On Fri, 20 Nov 2009 13:46:35 +0900 Tejun Heo <tj@kernel.org> wrote:

> ACPI works need to be executed on cpu0 and acpi/osl.c achieves this by
> creating singlethread workqueue and then binding it to cpu0 from a
> work which is quite unorthodox.  Make it create regular workqueues and
> use queue_work_on() instead.  This is in preparation of concurrency
> managed workqueue and the extra workers won't be a problem after it's
> implemented.
> 
> ...
>
>  acpi_status acpi_os_initialize1(void)
>  {
> -	/*
> -	 * On some machines, a software-initiated SMI causes corruption unless
> -	 * the SMI runs on CPU 0.  An SMI can be initiated by any AML, but
> -	 * typically it's done in GPE-related methods that are run via
> -	 * workqueues, so we can avoid the known corruption cases by binding
> -	 * the workqueues to CPU 0.
> -	 */
> -	kacpid_wq = create_singlethread_workqueue("kacpid");
> -	bind_workqueue(kacpid_wq);
> -	kacpi_notify_wq = create_singlethread_workqueue("kacpi_notify");
> -	bind_workqueue(kacpi_notify_wq);
> -	kacpi_hotplug_wq = create_singlethread_workqueue("kacpi_hotplug");
> -	bind_workqueue(kacpi_hotplug_wq);
> +	kacpid_wq = create_workqueue("kacpid");
> +	kacpi_notify_wq = create_workqueue("kacpi_notify");
> +	kacpi_hotplug_wq = create_workqueue("kacpi_hotplug");

Well that sucks.  We create an additional ((num_possible_cpus()-1)*3)
kernel threads just because the previous code was "unorthodox"?

I guess that problem goes away with concurrency-managed workqueues. 
But please let's not merge this patch without also merging
concurrency-managed workqueues!