linux-kernel - Re: [PATCH v2] workqueue: let WORKER_CPU

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Message-ID: <ZOURXUD7EfO0JVFE@slm.duckdns.org>
Date:   Tue, 22 Aug 2023 09:49:49 -1000
From:   Tejun Heo <tj@...nel.org>
To:     Tio Zhang <tiozhang@...iglobal.com>
Cc:     linux-kernel@...r.kernel.org, jiangshanlai@...il.com,
        zyhtheonly@...il.com, zyhtheonly@...h.net
Subject: Re: [PATCH v2] workqueue: let WORKER_CPU_INTENSIVE be included in
 watchdog

On Tue, Aug 22, 2023 at 07:06:51PM +0800, Tio Zhang wrote:
> When a pool has a worker with WORKER_CPU_INTENSIVE set but other workers
> are not that busy, the pool->worklist will mostly be empty, which leads
> the intensive work always having a chance of escaping from the watchdog's
> check. This may cause watchdog miss finding out a forever running work
> in WQ_CPU_INTENSIVE.
> 
> Also, after commit '616db8779b1e3f93075df691432cccc5ef3c3ba0',
> workers with potentially intensive works will automatically be converted
> into WORKER_CPU_INTENSIVE. This might let watchdog to miss all work
> potentially running forever.

The watchdog is there to ensure forward progress. CPU_INTENSIVE work items
don't block other work items, so I'm not sure why it should trigger the
watchdog.

Thanks.

-- 
tejun