linux-kernel - Re: [PATCH 4/5] workqueue: Automatically mark CPU-hogging work items CPU

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Date:   Mon, 24 Apr 2023 05:29:11 -1000
From:   Tejun Heo <tj@...nel.org>
To:     Lai Jiangshan <jiangshanlai@...il.com>
Cc:     torvalds@...ux-foundation.org, peterz@...radead.org,
        linux-kernel@...r.kernel.org, kernel-team@...a.com
Subject: Re: [PATCH 4/5] workqueue: Automatically mark CPU-hogging work items
 CPU_INTENSIVE

Hello, Lai.

On Sun, Apr 23, 2023 at 11:23:28AM +0800, Lai Jiangshan wrote:
> wq_worker_stopping() and sched_submit_work() are only called from
> schedule() and are not called for other various kinds of scheduling,
> such as schedule_rtlock(), preempt_schedule_*(), __cond_resched().
> 
> A work item hogging CPU may not call the bare schedule().  To make
> the new wq_worker_stopping() works, it has to be added to other kinds
> of scheduling, IMO.

Yeah, you're right. The proposed code would work fine only on !preempt
kernels. I guess the right thing to do is splitting out the hook for
non-sleeping schedulers and adding them in those paths. I'll look into it.

Thanks for spotting the issue.

-- 
tejun