linux-kernel - Re: [PATCH 15/21] workqueue: remove worker_maybe_bind_and

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Message-ID: <20130320181010.GA30484@htj.dyndns.org>
Date:	Wed, 20 Mar 2013 11:10:10 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 15/21] workqueue: remove worker_maybe_bind_and_lock()

On Wed, Mar 20, 2013 at 03:28:15AM +0800, Lai Jiangshan wrote:
>  static struct worker *alloc_worker(void)
>  {
>  	struct worker *worker;
> @@ -2326,7 +2262,8 @@ repeat:
>  		spin_unlock_irq(&wq_mayday_lock);
>  
>  		/* migrate to the target cpu if possible */
> -		worker_maybe_bind_and_lock(pool);
> +		set_cpus_allowed_ptr(current, pool->attrs->cpumask);
> +		spin_lock_irq(&pool->lock);
>  		rescuer->pool = pool;

You can't do this.  The CPU might go up between set_cpus_allowed_ptr()
and spin_lock_irq() and the rescuer can end up executing a work item
which was issued while the target CPU is up on the wrong CPU.

Thanks.

-- 
tejun
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