Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Sender: Tejun Heo <htejun@gmail.com>
Date:   Tue, 23 May 2023 11:37:14 -1000
From:   Tejun Heo <tj@kernel.org>
To:     Lai Jiangshan <jiangshanlai@gmail.com>
Cc:     torvalds@linux-foundation.org, peterz@infradead.org,
        linux-kernel@vger.kernel.org, kernel-team@meta.com,
        joshdon@google.com, brho@google.com, briannorris@chromium.org,
        nhuck@google.com, agk@redhat.com, snitzer@kernel.org,
        void@manifault.com
Subject: Re: [PATCH 03/24] workqueue: Not all work insertion needs to wake up
 a worker
Message-ID: <ZG0yCiRI8apvfWkq@slm.duckdns.org>
References: <20230519001709.2563-1-tj@kernel.org>
 <20230519001709.2563-4-tj@kernel.org>
 <CAJhGHyCdgfNY83ddpQRpsCVvPQF9HtuNXXFFbpJuxYLL+mYcZQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <CAJhGHyCdgfNY83ddpQRpsCVvPQF9HtuNXXFFbpJuxYLL+mYcZQ@mail.gmail.com>
Precedence: bulk

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@kernel.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