linux-kernel - Re: [RFC PATCH] workqueue: Fix rescuer task's name truncated

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Date: Wed, 24 Apr 2024 08:12:40 +0100
From: Aaron Tomlin <atomlin@...mlin.com>
To: Wenchao Hao <haowenchao2@...wei.com>
Cc: Tejun Heo <tj@...nel.org>, Lai Jiangshan <jiangshanlai@...il.com>, 
	linux-kernel@...r.kernel.org, Wenchao Hao <haowenchao22@...il.com>, neelx@...hat.com
Subject: Re: [RFC PATCH] workqueue: Fix rescuer task's name truncated

On Tue, Apr 23, 2024 at 12:55:22PM +0800, Wenchao Hao wrote:
> Hi Tejun and all:
> 
> I added another logic in wq_worker_comm() to append worker's desc when
> worker is not attached to a work pool. I don't know why the origin
> logic only append worker's desc when worker is attached to a work pool,
> so I am not sure if it's safe to using worker here directly.

Hi Wenchao,

A worker description is always updated under the per-pool workqueue lock.
You can indeed use the rescuer's own description to store its associated
workqueue name - good idea. We know the caller of set_worker_desc() will
never touch a rescuer. For this unique rescuer case, if I understand
correctly, you can read a rescuer's description outside the per-pool
workqueue lock; albeit, you need to prevent a race with destroy_workqueue()
to avoid a use-after-free.

Kind regards,

-- 
Aaron Tomlin