linux-kernel - Re: [PATCH] kernel: Introduce enable_and_queue

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Date: Thu, 29 Feb 2024 10:30:35 +0800
From: Lai Jiangshan <jiangshanlai@...il.com>
To: Allen Pais <apais@...ux.microsoft.com>
Cc: tj@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kernel: Introduce enable_and_queue_work() convenience function

On Thu, Feb 29, 2024 at 2:18 AM Allen Pais <apais@...ux.microsoft.com> wrote:
>
> The enable_and_queue_work() function is introduced to streamline
> the process of enabling and queuing a work item on a specific
> workqueue. This function combines the functionalities of
> enable_work() and queue_work() in a single call, providing a
> concise and convenient API for enabling and queuing work items.
>
> The function accepts a target workqueue and a work item as parameters.
> It first attempts to enable the work item using enable_work(). If the
> enable operation is successful, the work item is then queued on the
> specified workqueue using queue_work(). The function returns true if
> the work item was successfully enabled and queued, and false otherwise.
>
> This addition aims to enhance code readability and maintainability by
> providing a unified interface for the common use case of enabling and
> queuing work items on a workqueue.
>
> Signed-off-by: Allen Pais <allen.lkml@...il.com>
> ---
>  include/linux/workqueue.h | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
>
> diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
> index aedfb81f9c49..31bbd38ef8c8 100644
> --- a/include/linux/workqueue.h
> +++ b/include/linux/workqueue.h
> @@ -678,6 +678,29 @@ static inline bool schedule_work(struct work_struct *work)
>         return queue_work(system_wq, work);
>  }
>
> +/**
> + * enable_and_queue_work - Enable and queue a work item on a specific workqueue
> + * @wq: The target workqueue
> + * @work: The work item to be enabled and queued
> + *
> + * This function attempts to enable the specified work item using enable_work().
> + * If the enable operation is successful, the work item is then queued on the

Could you please specify what "successful" means and also please
document it that it might cause unnecessary spurious wake-ups and
the caller should prepare for it if it is not desired.

Thanks
Lai

PS:

I'm afraid it can cause unnecessary spurious wake-ups in cases
where the work item is expected to be dormant ordinarily but disable/enable()
are called often for maintenance.  However, the user can resort to other
synchronization in this case rather than just disable/enable() only to avoid the
wake-ups overheads.



> + * provided workqueue using queue_work(). It returns %true if the work item was
> + * successfully enabled and queued, and %false otherwise.
> + *
> + * This function combines the operations of enable_work() and queue_work(),
> + * providing a convenient way to enable and queue a work item in a single call.
> + */
> +static inline bool enable_and_queue_work(struct workqueue_struct *wq,
> +                                        struct work_struct *work)
> +{
> +       if (enable_work(work)) {
> +               queue_work(wq, work);
> +               return true;
> +       }
> +       return false;
> +}
> +
>  /*
>   * Detect attempt to flush system-wide workqueues at compile time when possible.
>   * Warn attempt to flush system-wide workqueues at runtime.
> --
> 2.17.1
>