linux-kernel - Re: [PATCH 37/38] workqueue: Replace deprecated CPU-hotplug functions.

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Date:   Wed, 4 Aug 2021 09:36:21 +0800
From:   Lai Jiangshan <jiangshanlai@...il.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH 37/38] workqueue: Replace deprecated CPU-hotplug functions.

On Tue, Aug 3, 2021 at 10:17 PM Sebastian Andrzej Siewior
<bigeasy@...utronix.de> wrote:
>
> The functions get_online_cpus() and put_online_cpus() have been
> deprecated during the CPU hotplug rework. They map directly to
> cpus_read_lock() and cpus_read_unlock().
>
> Replace deprecated CPU-hotplug functions with the official version.
> The behavior remains unchanged.
>
> Cc: Tejun Heo <tj@...nel.org>
> Cc: Lai Jiangshan <jiangshanlai@...il.com>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> ---


Reviewed-by: Lai Jiangshan <jiangshanlai@...il.com>

>  kernel/workqueue.c | 22 +++++++++++-----------
>  1 file changed, 11 insertions(+), 11 deletions(-)
>
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index f148eacda55a9..f967aa4050d08 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -3293,7 +3293,7 @@ int schedule_on_each_cpu(work_func_t func)
>         if (!works)
>                 return -ENOMEM;
>
> -       get_online_cpus();
> +       cpus_read_lock();
>
>         for_each_online_cpu(cpu) {
>                 struct work_struct *work = per_cpu_ptr(works, cpu);
> @@ -3305,7 +3305,7 @@ int schedule_on_each_cpu(work_func_t func)
>         for_each_online_cpu(cpu)
>                 flush_work(per_cpu_ptr(works, cpu));
>
> -       put_online_cpus();
> +       cpus_read_unlock();
>         free_percpu(works);
>         return 0;
>  }
> @@ -4016,14 +4016,14 @@ static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
>  static void apply_wqattrs_lock(void)
>  {
>         /* CPUs should stay stable across pwq creations and installations */
> -       get_online_cpus();
> +       cpus_read_lock();
>         mutex_lock(&wq_pool_mutex);
>  }
>
>  static void apply_wqattrs_unlock(void)
>  {
>         mutex_unlock(&wq_pool_mutex);
> -       put_online_cpus();
> +       cpus_read_unlock();
>  }
>
>  static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
> @@ -4068,7 +4068,7 @@ static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
>   *
>   * Performs GFP_KERNEL allocations.
>   *
> - * Assumes caller has CPU hotplug read exclusion, i.e. get_online_cpus().
> + * Assumes caller has CPU hotplug read exclusion, i.e. cpus_read_lock().
>   *
>   * Return: 0 on success and -errno on failure.
>   */
> @@ -4196,7 +4196,7 @@ static int alloc_and_link_pwqs(struct workqueue_struct *wq)
>                 return 0;
>         }
>
> -       get_online_cpus();
> +       cpus_read_lock();
>         if (wq->flags & __WQ_ORDERED) {
>                 ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);
>                 /* there should only be single pwq for ordering guarantee */
> @@ -4206,7 +4206,7 @@ static int alloc_and_link_pwqs(struct workqueue_struct *wq)
>         } else {
>                 ret = apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
>         }
> -       put_online_cpus();
> +       cpus_read_unlock();
>
>         return ret;
>  }
> @@ -5168,10 +5168,10 @@ long work_on_cpu_safe(int cpu, long (*fn)(void *), void *arg)
>  {
>         long ret = -ENODEV;
>
> -       get_online_cpus();
> +       cpus_read_lock();
>         if (cpu_online(cpu))
>                 ret = work_on_cpu(cpu, fn, arg);
> -       put_online_cpus();
> +       cpus_read_unlock();
>         return ret;
>  }
>  EXPORT_SYMBOL_GPL(work_on_cpu_safe);
> @@ -5443,7 +5443,7 @@ static ssize_t wq_pool_ids_show(struct device *dev,
>         const char *delim = "";
>         int node, written = 0;
>
> -       get_online_cpus();
> +       cpus_read_lock();
>         rcu_read_lock();
>         for_each_node(node) {
>                 written += scnprintf(buf + written, PAGE_SIZE - written,
> @@ -5453,7 +5453,7 @@ static ssize_t wq_pool_ids_show(struct device *dev,
>         }
>         written += scnprintf(buf + written, PAGE_SIZE - written, "\n");
>         rcu_read_unlock();
> -       put_online_cpus();
> +       cpus_read_unlock();
>
>         return written;
>  }
> --
> 2.32.0
>