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From:   Aaron Tomlin <atomlin@atomlin.com>
To:     peterz@infradead.org, tj@kernel.org
Cc:     atomlin@atomlin.com, jiangshanlai@gmail.com,
        linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 1/2] workqueue: Introduce PF_WQ_RESCUE_WORKER
Date:   Tue,  1 Aug 2023 11:04:20 +0100
Message-Id: <20230801100420.939677-1-atomlin@atomlin.com>
In-Reply-To: <20230729160712.GA5697@hirez.programming.kicks-ass.net>
References: <20230729160712.GA5697@hirez.programming.kicks-ass.net>
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> Is the implication that PF_flags are considered ABI? We've been changing
> them quite a bit over the years.

Hi Peter, Tejun,

I never assumed they were.

In this context, one should always check the Linux kernel source code first
i.e. do not assume what is exported via /proc/[PID]/stat will be stable/or
consistent between releases.

> Also, while we have a few spare bits atm, we used to be nearly out for a
> while, and I just don't think this is sane usage of them. We don't use PF
> flags just for userspace.

Fair statement.

Albeit, I suspect it would still be useful for user-mode to easily
differentiate between a kworker and a rescuer kworker. According to
create_worker(), we do make it clear the difference between a CPU-specific
and unbound kworker by way of the task's name. Looking at init_rescuer() a
rescuer kworker is simply given the name of its workqueue. Would you
consider modifying the rescuer's task's name so it is prefixed with
"kworker/r-%s" and then include the workqueue's name e.g.
"kworker/r-ext4-rsv-conver" acceptable?


Kind regards,
-- 
Aaron Tomlin