linux-kernel - Re: [PATCH] workqueue: Rename rescuer kworker

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Date:   Tue,  8 Aug 2023 12:24:21 +0100
From:   Aaron Tomlin <atomlin@...mlin.com>
To:     tj@...nel.org
Cc:     atomlin@...mlin.com, jiangshanlai@...il.com,
        linux-kernel@...r.kernel.org, peterz@...radead.org
Subject: Re: [PATCH] workqueue: Rename rescuer kworker

> I'm not necessarily against the rename but you can't, or at least
> shouldn't, modify the cpu affinity of any workqueue worker. You don't
> know what that worker is going to be executing even at the moment when
> the cpu affinity change is committed, let alone in any future. Can you
> please drop that part from the patch description? It doesn't make a lot
> of sense.

Hi Tejun,

Understood - will do. Initially, I wanted to stress the point that
user-mode should not pay any attention to a rescuer kworker's CPU affinity
since by design it can run on any possible CPU.
According to housekeeping_setup() and workqueue_init_early(), if I
understand correctly, when kernel parameter nohz_full is set then each
unbound kworker is not permitted to execute on any CPU in the specified
range i.e. the unbound workqueue cpumask is set based on the housekeeping
cpumask only. So, that's good enough.

Kind regards,

-- 
Aaron Tomlin