Re: [PATCH] mm: Introduce dedicated WQ_MEM_RECLAIM workqueue to do lru_add_drain_all

[Tejun Heo <tj@kernel.org>]

On Thu, Jun 02, 2016 at 03:48:51PM +0800, Wang Sheng-Hui wrote:
> +static int __init lru_init(void)
> +{
> +	lru_add_drain_wq = alloc_workqueue("lru-add-drain",
> +		WQ_MEM_RECLAIM | WQ_UNBOUND, 0);

Why is it unbound?

> +	if (WARN(!lru_add_drain_wq,
> +		"Failed to create workqueue lru_add_drain_wq"))
> +		return -ENOMEM;

I don't think we need an explicit warn here.  Doesn't error return
from an init function trigger boot failure anyway?

> +	return 0;
> +}
> +early_initcall(lru_init);
> +
>  void lru_add_drain_all(void)
>  {
>  	static DEFINE_MUTEX(lock);
>  	static struct cpumask has_work;
>  	int cpu;
>  
> +	struct workqueue_struct *lru_wq = lru_add_drain_wq ?: system_wq;
> +
> +	WARN_ONCE(!lru_add_drain_wq,
> +		"Use system_wq to do lru_add_drain_all()");

Ditto.  The system is crashing for sure.  What's the point of this
warning?

Thanks.

-- 
tejun

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