linux-kernel - Re: [PATCH 03/24] workqueue: Not all work insertion needs to wake up a worker

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Message-ID: <ZG0yCiRI8apvfWkq@slm.duckdns.org>
Date:   Tue, 23 May 2023 11:37:14 -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,
        joshdon@...gle.com, brho@...gle.com, briannorris@...omium.org,
        nhuck@...gle.com, agk@...hat.com, snitzer@...nel.org,
        void@...ifault.com
Subject: Re: [PATCH 03/24] workqueue: Not all work insertion needs to wake up
 a worker

On Tue, May 23, 2023 at 05:54:10PM +0800, Lai Jiangshan wrote:
> On Fri, May 19, 2023 at 8:17 AM Tejun Heo <tj@...nel.org> wrote:
> 
> > +       pool = pwq->pool;
> > +
> >         /*
> >          * If @work was previously on a different pool, it might still be
> >          * running there, in which case the work needs to be queued on that
> >          * pool to guarantee non-reentrancy.
> >          */
> >         last_pool = get_work_pool(work);
> > -       if (last_pool && last_pool != pwq->pool) {
> > +       if (last_pool && last_pool != pool) {
> >                 struct worker *worker;
> >
> >                 raw_spin_lock(&last_pool->lock);
> > @@ -1638,13 +1636,14 @@ static void __queue_work(int cpu, struct workqueue_struct *wq,
> >
> >                 if (worker && worker->current_pwq->wq == wq) {
> >                         pwq = worker->current_pwq;
> > +                       pool = pwq->pool;
> 
> The code above does a "raw_spin_lock(&last_pool->lock);", and
> the code next does a "raw_spin_unlock(&pool->lock);".
> 
>                             WARN_ON_ONCE(pool != last_pool);
> 
> can be added here and served as a comment.

Yeah, this is a bit confusing. Added WARN_ON_ONCE().

Thanks.

-- 
tejun