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References: <20230519001709.2563-1-tj@kernel.org> <20230519001709.2563-4-tj@kernel.org>
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From:   Lai Jiangshan <jiangshanlai@gmail.com>
Date:   Tue, 23 May 2023 17:54:10 +0800
Message-ID: <CAJhGHyCdgfNY83ddpQRpsCVvPQF9HtuNXXFFbpJuxYLL+mYcZQ@mail.gmail.com>
Subject: Re: [PATCH 03/24] workqueue: Not all work insertion needs to wake up
 a worker
To:     Tejun Heo <tj@kernel.org>
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
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On Fri, May 19, 2023 at 8:17=E2=80=AFAM Tejun Heo <tj@kernel.org> wrote:

> +       pool =3D 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 th=
at
>          * pool to guarantee non-reentrancy.
>          */
>         last_pool =3D get_work_pool(work);
> -       if (last_pool && last_pool !=3D pwq->pool) {
> +       if (last_pool && last_pool !=3D pool) {
>                 struct worker *worker;
>
>                 raw_spin_lock(&last_pool->lock);
> @@ -1638,13 +1636,14 @@ static void __queue_work(int cpu, struct workqueu=
e_struct *wq,
>
>                 if (worker && worker->current_pwq->wq =3D=3D wq) {
>                         pwq =3D worker->current_pwq;
> +                       pool =3D 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 !=3D last_pool);

can be added here and served as a comment.

>                 } else {
>                         /* meh... not running there, queue here */
>                         raw_spin_unlock(&last_pool->lock);
> -                       raw_spin_lock(&pwq->pool->lock);
> +                       raw_spin_lock(&pool->lock);
>                 }
>         } else {
> -               raw_spin_lock(&pwq->pool->lock);
> +               raw_spin_lock(&pool->lock);
>         }
>