linux-kernel - Re: [PATCH 4/4 V6] workqueue: Allow modifying low level unbound workqueue cpumask

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Date:	Mon, 6 Apr 2015 21:58:17 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org, Christoph Lameter <cl@...ux.com>,
	Kevin Hilman <khilman@...aro.org>,
	Mike Galbraith <bitbucket@...ine.de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 4/4 V6] workqueue: Allow modifying low level unbound
 workqueue cpumask

Hello, Lai.

On Tue, Apr 07, 2015 at 09:25:59AM +0800, Lai Jiangshan wrote:
> On 04/06/2015 11:53 PM, Tejun Heo wrote:
> > On Thu, Apr 02, 2015 at 07:14:42PM +0800, Lai Jiangshan wrote:
> >>  	/* make a copy of @attrs and sanitize it */
> >>  	copy_workqueue_attrs(new_attrs, attrs);
> >> -	cpumask_and(new_attrs->cpumask, new_attrs->cpumask, wq_unbound_global_cpumask);
> >> +	copy_workqueue_attrs(pwq_attrs, attrs);
> >> +	cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
> >> +	cpumask_and(pwq_attrs->cpumask, pwq_attrs->cpumask, unbound_cpumask);
> > 
> > Hmmm... why do we need to keep track of both cpu_possible_mask and
> > unbound_cpumask?  Can't we just make unbound_cpumask replace
> > cpu_possible_mask for unbound workqueues?
> > 
> 
> I want to save the original user-setting cpumask.
> 
> When any time the wq_unbound_global_cpumask is changed,
> the new effective cpumask is
> the-original-user-setting-cpumask & wq_unbound_global_cpumask
> instead of
> the-last-effective-cpumask & wq_unbound_global_cpumask.

Yes, I get that, but that'd require just tracking the original
configured value and the unbound_cpumask masked value, no?  What am I
missing?

Thanks.

-- 
tejun
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