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From:   Lai Jiangshan <jiangshanlai@gmail.com>
Date:   Tue, 6 Dec 2022 14:23:39 +0800
Message-ID: <CAJhGHyAVbCm6i7pTRDDXgdwS25d5O3uMCvKzyOcafRAdN-S7JQ@mail.gmail.com>
Subject: Re: work item still be scheduled to execute after destroy_workqueue?
To:     richard clark <richard.xnu.clark@gmail.com>
Cc:     tj@kernel.org, linux-kernel@vger.kernel.org
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On Tue, Dec 6, 2022 at 12:35 PM richard clark
<richard.xnu.clark@gmail.com> wrote:

> >
> A WARN is definitely reasonable and has its benefits. Can I try to
> submit the patch and you're nice to review as maintainer?
>
> Thanks,
> Richard
> >

Sure, go ahead.

What's in my mind is that the following code is wrapped in a new function:

        mutex_lock(&wq->mutex);
        if (!wq->nr_drainers++)
                wq->flags |= __WQ_DRAINING;
        mutex_unlock(&wq->mutex);


and the new function replaces the open code drain_workqueue() and
is also called in destroy_workqueue() (before calling drain_workqueue()).


__WQ_DRAINING will cause the needed WARN on illegally queuing items on
destroyed workqueue.

Thanks
Lai