linux-kernel - Re: [PATCH 2/6] workqueue: Protect wq_unbound_cpumask with wq_pool_attach_mutex in init

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Message-ID: <7b105f07-5c13-4f69-9834-05e7054ddb36@redhat.com>
Date: Wed, 3 Jul 2024 11:14:44 -0400
From: Waiman Long <longman@...hat.com>
To: Lai Jiangshan <jiangshanlai@...il.com>, linux-kernel@...r.kernel.org
Cc: Lai Jiangshan <jiangshan.ljs@...group.com>, Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH 2/6] workqueue: Protect wq_unbound_cpumask with
 wq_pool_attach_mutex in init_rescuer()


On 7/2/24 23:38, Lai Jiangshan wrote:
> From: Lai Jiangshan <jiangshan.ljs@...group.com>
>
> wq_unbound_cpumask can be possibly changed without wq_pool_attach_mutex
> or wq_pool_mutex held in init_rescuer().
>
> Use wq_pool_attach_mutex to protect it.
>
> Fixes: 49584bb8ddbe("workqueue: Bind unbound workqueue rescuer to wq_unbound_cpumask")
> Signed-off-by: Lai Jiangshan <jiangshan.ljs@...group.com>
> ---
>   kernel/workqueue.c | 5 +++++
>   1 file changed, 5 insertions(+)
>
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index c738b3024cc2..cf1a129eb547 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -5533,6 +5533,9 @@ static int init_rescuer(struct workqueue_struct *wq)
>   		return ret;
>   	}
>   
> +	/* lock wq_pool_attach_mutex for wq_unbound_cpumask */
> +	mutex_lock(&wq_pool_attach_mutex);
> +
>   	wq->rescuer = rescuer;
>   	if (wq->flags & WQ_UNBOUND)
>   		kthread_bind_mask(rescuer->task, wq_unbound_cpumask);
> @@ -5540,6 +5543,8 @@ static int init_rescuer(struct workqueue_struct *wq)
>   		kthread_bind_mask(rescuer->task, cpu_possible_mask);
>   	wake_up_process(rescuer->task);
>   
> +	mutex_unlock(&wq_pool_attach_mutex);
> +
>   	return 0;
>   }
>   
Reviewed-by: Waiman Long <longman@...hat.com>

Thanks!