linux-kernel - Re: [PATCH 3/4] workqueue: Allow modifying low level unbound workqueue cpumask

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Date:	Thu, 24 Apr 2014 11:30:48 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Christoph Lameter <cl@...ux.com>,
	Kevin Hilman <khilman@...aro.org>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Mike Galbraith <bitbucket@...ine.de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Viresh Kumar <viresh.kumar@...aro.org>
Subject: Re: [PATCH 3/4] workqueue: Allow modifying low level unbound
 workqueue cpumask

On Thu, Apr 24, 2014 at 04:37:35PM +0200, Frederic Weisbecker wrote:
> +static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
> +					const struct workqueue_attrs *attrs);

Can't we reorder things so that we don't need the above prototype?

> +/* Must be called with wq_unbound_mutex held */

Please use lockdep_assert_held() instead.

> +static int unbounds_cpumask_apply_all(cpumask_var_t cpumask)
> +{
> +	struct workqueue_struct *wq;
> +
> +	list_for_each_entry(wq, &workqueues, list) {
> +		struct workqueue_attrs *attrs;
> +
> +		if (!(wq->flags & WQ_UNBOUND))
> +			continue;
> +		/* Ordered workqueues need specific treatment */
> +		if (wq->flags & __WQ_ORDERED)
> +			continue;
> +
> +		attrs = wq_sysfs_prep_attrs(wq);
> +		if (!attrs)
> +			return -ENOMEM;

So, we're failing in the middle without rolling back?

> +
> +		WARN_ON_ONCE(apply_workqueue_attrs_locked(wq, attrs));

Are we triggering WARN on -ENOMEM too and then ignore the failure?

> +		free_workqueue_attrs(attrs);
> +	}
> +
> +	return 0;
> +}

Shouldn't we separate allocation stage from switching stage so that we
can either succeed or fail?  The above is very mushy about error
handling.

Thanks.

-- 
tejun
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